阅读说明：本技术 二次电池的阴极的制备方法 (Method for preparing cathode of secondary battery ) 是由 何锦镖 江英凯 于 2020-05-22 设计创作，主要内容包括：本文提供了一种基于水性浆料制备阴极的方法。本发明提供了一种阴极浆料,其包含在水中具有改善的稳定性的阴极活性材料,特别是含镍的阴极活性材料。使用锂化合物处理含镍阴极活性材料可以通过防止材料的不期望的分解来改善阴极的稳定性。另外,包含通过本文公开的方法制备的阴极的电池显示出优异的电化学性能。(A method for preparing a cathode based on an aqueous slurry is provided. The present invention provides a cathode slurry comprising a cathode active material having improved stability in water, particularly a cathode active material containing nickel. Treating a nickel-containing cathode active material with a lithium compound can improve the stability of the cathode by preventing undesirable decomposition of the material. In addition, batteries comprising cathodes prepared by the methods disclosed herein exhibit excellent electrochemical performance.)

1. A method of preparing a cathode for a secondary battery, comprising the steps of:

1) dispersing a binder material and a conductive agent in water to form a first suspension;

2) adding an aqueous solution comprising at least one lithium compound to the first suspension to form a second suspension;

3) adding a cathode active material to the second suspension to form a third suspension;

4) homogenizing the third suspension by a homogenizer to obtain a homogenized slurry;

5) coating the homogenized slurry on a current collector to form a coating film on the current collector; and is

6) Drying the coating film on the current collector to form the cathode,

wherein the lithium compound is selected from the group consisting of lithium borate, lithium bromide, lithium chloride, lithium bicarbonate, lithium hydroxide, lithium iodide, lithium nitrate, lithium sulfate, lithium acetate, lithium lactate, lithium citrate, lithium succinate, and combinations thereof.

2. The method of claim 1, wherein the cathode active material is selected from the group consisting of Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂、LiNi_0.33Mn_0.33Co_0.33O₂、LiNi_0.4Mn_0.4Co_0.2O₂、LiNi_0.5Mn_0.3Co_0.2O₂、LiNi_0.6Mn_0.2Co_0.2O₂、LiNi_0.7Mn_0.15Co_0.15O₂、LiNi_0.8Mn_0.1Co_0.1O₂、LiNi_0.92Mn_0.04Co_0.04O₂、LiNi_0.8Co_0.15Al_0.05O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃And combinations thereof; wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1.

3. The method of claim 1, wherein the cathode active material comprises or is itself a core-shell composite having a core and shell structure, wherein each of the core and the shell independently comprises Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃、LiCrO₂、Li₄Ti₅O₁₂、LiV₂O₅、LiTiS₂、LiMoS₂And combinations thereof; wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1.

4. The method of claim 1, wherein the solubility of the lithium compound in water is greater than 1g/100mL at 20 ℃, and the concentration of lithium ions in the second suspension is in the range of about 0.0005M to about 0.5M.

5. The method of claim 1, wherein the mixing in step 2) is at a temperature of about 5 ℃ to about 30 ℃ for a period of about 5 minutes to about 60 minutes, and wherein the pH of the second suspension is about 7 to about 13.

6. The method of claim 1, wherein the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof.

7. The method of claim 1, further comprising the step of degassing the third suspension under vacuum at a pressure of about 1kPa to about 20kPa for about 30 minutes to about 4 hours.

8. The method of claim 1, wherein the third suspension is homogenized at a temperature of about 10 ℃ to about 30 ℃ for a period of about 30 minutes to about 6 hours.

9. The method of claim 1, wherein the solids content of the homogenized slurry is about 45% to about 75% by weight based on the total weight of the homogenized slurry, and wherein the homogenized slurry is free of dispersants, wherein the dispersants are selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and polymeric acids.

10. The process of claim 1, wherein the pH reduction of step 4) is observed to be about 0.1 to about 1.0, and wherein the pH of the homogenized slurry is about 8 to about 14.

11. The method of claim 1, wherein the coating film on the current collector is dried at a temperature of about 25 ℃ to about 75 ℃ for about 2 minutes to about 20 minutes.

12. The method of claim 1, wherein the total processing time of steps 3) -6) is less than 5 hours.

Technical Field

The present invention relates to the field of batteries. In particular, the present invention relates to a method of making a cathode for a lithium ion battery.

Background

In the past decades, Lithium Ion Batteries (LIBs) have been widely used in a variety of applications, particularly consumer electronics, due to their excellent energy density, long cycle life and high discharge capacity. Due to the rapid market development of Electric Vehicles (EVs) and grid energy storage, high performance, low cost LIBs currently provide one of the most promising options for large-scale energy storage devices.

The use of multiple lithium transition metal oxides such as lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminum oxide (NCA) has become popular because of their superior electrochemical properties over, for example, LiMnO₂、LiCoO₂And LiNiO₂Conventional cathode active materials. Excellent electrochemical properties include high energy density and excellent capacity performance.

Currently, a cathode is generally prepared by dispersing a cathode active material, a binder material, and a conductive agent in an organic solvent, such as N-methyl-2-pyrrolidone (NMP), to prepare a cathode slurry, and then coating the cathode slurry on a current collector and drying.

For environmental and ease of handling reasons, it is preferred to use aqueous solutions instead of organic solvents, and thus water-based slurries have been considered. However, a cathode active material containing nickel may react with water during electrode preparation, which may cause metals in the cathode active material to leach out of the cathode active material and cause performance degradation. Dissolution of lithium at the surface of the cathode active material results in the formation of a soluble base. A high content of soluble alkali increases the pH of the cathode slurry, which may affect the dispersion uniformity of components (e.g., cathode active material) in the cathode slurry, and the binding power of the binder material. Also, the metal components of the electrode (e.g., current collector) and, thus, the performance of the cathode active material, are adversely affected. For example, cathodesThe active material reacts with the aluminum current collector to form Al (OH)₃Precipitation, which hinders the transport of lithium ions, thereby lowering the capacity retention rate of the battery. Both of these factors result in poor electrochemical performance. Conventionally, a pH adjuster is used to adjust the pH of the cathode slurry. However, the additives may also adversely affect the electrochemical processes occurring at the cathode, especially at high voltages and temperatures, which in turn reduces the battery performance. Accordingly, it is desirable to prevent lithium from dissolving from the surface of the cathode active material during the preparation of the cathode slurry.

European patent application publication No. 3044822a discloses a water-based lithium transition metal oxide cathode slurry. The slurry comprises a lithium transition metal oxide powder consisting of primary particles containing a coating comprising a polymer. The coating consists of two layers. The outer layer comprises a fluoropolymer that prevents the pH-raised ion exchange reaction with water by reducing the surface coverage of the water. The inner layer comprises the reaction product between the polymer of the outer layer and the lithium transition metal oxide, such as LiF, wherein the reaction decomposes the alkali at the surface and lowers the alkali potential of the oxide. However, fluoropolymers increase electrical resistance, resulting in decreased battery performance and posing a risk to human health and the environment.

In view of the above, there is always a need to develop a cathode slurry containing a nickel cathode active material for a lithium ion battery having good electrochemical properties using a simple, rapid and environmentally friendly method.

Disclosure of Invention

The foregoing needs are met by the various aspects and embodiments disclosed herein. In one aspect, provided herein is a method of preparing a cathode for a secondary battery, comprising the steps of:

1) dispersing a binder material and a conductive agent in water to form a first suspension;

2) adding an aqueous solution comprising at least one lithium compound to the first suspension to form a second suspension;

3) adding a cathode active material to the second suspension to form a third suspension;

4) homogenizing the third suspension by a homogenizer to obtain a homogenized slurry;

5) coating the homogenized slurry on a current collector to form a coating film on the current collector; and is

6) Drying the coating film on the current collector to form a cathode,

wherein the lithium compound is selected from the group consisting of lithium borate, lithium bromide, lithium chloride, lithium bicarbonate, lithium hydroxide, lithium iodide, lithium nitrate, lithium sulfate, lithium acetate, lithium lactate, lithium citrate, lithium succinate, and combinations thereof.

In some embodiments, the cathode active material is selected from the group consisting of Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂、LiNi_0.33Mn_0.33Co_0.33O₂、LiNi_0.4Mn_0.4Co_0.2O₂、LiNi_0.5Mn_0.3Co_0.2O₂、LiNi_0.6Mn_0.2Co_0.2O₂、LiNi_0.7Mn_0.15Co_0.15O₂、LiNi_0.8Mn_0.1Co_0.1O₂、LiNi_0.92Mn_0.04Co_0.04O₂、LiNi_0.8Co_0.15Al_0.05O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃And combinations thereof; wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1. In a further embodiment, the cathode active material comprises or is itself a core-shell composite having a core and shell structure, wherein each of the core and shell independently comprises Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃、LiCrO₂、Li₄Ti₅O₁₂、LiV₂O₅、LiTiS₂、LiMoS₂And combinations thereof; wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1.

In certain embodiments, the solubility of the lithium compound in water at 20 ℃ is greater than 1g/100 mL. In some embodiments, the concentration of lithium ions in the second suspension is in the range of about 0.0005M to about 0.5M.

In some embodiments, the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof.

In certain embodiments, the mixing in step 2) is at a temperature of about 5 ℃ to about 30 ℃ for a period of about 5 minutes to about 60 minutes. In some embodiments, the pH of the second suspension is from about 7 to about 13.

In some embodiments, the third suspension is homogenized at a temperature of about 10 ℃ to about 30 ℃ for a period of about 30 minutes to about 6 hours. In certain embodiments, the methods provided herein further comprise the step of degassing the third suspension under vacuum at a pressure of about 1kPa to about 20kPa for about 30 minutes to about 4 hours.

In certain embodiments, the pH reduction of step 4) is observed to be from about 0.1 to about 1.0. In some embodiments, the solids content of the homogenized slurry is about 45% to about 75% by weight, based on the total weight of the homogenized slurry. In a further embodiment, the pH of the homogenized slurry is from about 8 to about 14.

In some embodiments, the homogenized slurry is free of dispersants, wherein the dispersants are selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and polymeric acids.

In certain embodiments, the coating film on the current collector is dried at a temperature of about 25 ℃ to about 75 ℃ for about 2 minutes to about 20 minutes.

In some embodiments, the total processing time of steps 3) -6) is less than 5 hours.

Drawings

Fig. 1 is a flow chart showing one embodiment of the steps of preparing a cathode.

Figure 2 depicts the D50 particle size distributions for the organic and alkali treated slurries, respectively.

Fig. 3 is a bar graph showing the peel strength of electrodes prepared by different methods.

Fig. 4 shows three specific capacity-voltage curves for the first discharge cycle of NMC 811.

FIG. 5 shows data on infrared spectra of polyacrylamide after mixing with LiOH.

Fig. 6 shows infrared spectral data of polyacrylamide after mixing with LiI.

Detailed Description

Provided herein is a method of preparing a cathode for a secondary battery, comprising the steps of:

1) dispersing a binder material and a conductive agent in water to form a first suspension;

2) adding an aqueous solution comprising at least one lithium compound to the first suspension to form a second suspension;

3) adding a cathode active material to the second suspension to form a third suspension;

4) homogenizing the third suspension by a homogenizer to obtain a homogenized slurry;

5) coating the homogenized slurry on a current collector to form a coating film on the current collector; and is

6) Drying the coating film on the current collector to form a cathode,

wherein the lithium compound is selected from the group consisting of lithium borate, lithium bromide, lithium chloride, lithium bicarbonate, lithium hydroxide, lithium iodide, lithium nitrate, lithium sulfate, lithium acetate, lithium lactate, lithium citrate, lithium succinate, and combinations thereof.

The term "electrode" refers to either the "cathode" or the "anode".

The term "cathode" is used interchangeably with cathode. Also, the term "negative electrode" is used interchangeably with anode.

The term "binder material" refers to a chemical or substance that can hold the electrode material and/or conductive agent in place and adhere both to the conductive metal part to form an electrode. In some embodiments, the electrode does not contain any conductive agent.

The term "conductive agent" refers to a material that is chemically inert and has good electrical conductivity. Therefore, the conductive agent is generally mixed with the electrode active material when forming the electrode to improve the conductivity of the electrode.

"Polymer" means a polymeric compound prepared by polymerizing monomers of the same or different types. The generic term "polymer" includes the terms "homopolymer," copolymer, "" terpolymer, "and" interpolymer.

"interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. The generic term "interpolymer" encompasses the term "copolymer" (generally referring to a polymer prepared from two different monomers) as well as the term "terpolymer" (generally referring to a polymer prepared from three different types of monomers). It also includes polymers prepared by polymerizing four or more types of monomers.

The term "homogenizer" refers to an apparatus that can be used for homogenization of a material. The term "homogenization" refers to a process of uniformly distributing material throughout a fluid. Any conventional homogenizer may be used in the methods disclosed herein. Some non-limiting examples of homogenizers include stirred mixers, planetary stirred mixers, and sonicators.

The term "planetary mixer" refers to a device that can be used to mix or stir different materials to produce a homogenized mixture, consisting of paddles that perform a planetary motion within a vessel. In some embodiments, the planetary mixer comprises at least one planetary paddle and at least one high speed dispersing paddle. Planetary paddles and high speed dispersing paddles rotate about their own axis and also rotate continuously around the vessel. The rotation speed may be expressed in revolutions per minute (rpm), which refers to the number of rotations the rotating body completes in one minute.

The term "sonicator" refers to a device that can apply ultrasonic energy to agitate particles in a sample. Any sonicator that can disperse the slurries disclosed herein can be used herein. Some non-limiting examples of ultrasonic generators include ultrasonic baths, probe-type ultrasonic generators, and ultrasonic flow cells.

The term "ultrasonic bath" refers to a device through which ultrasonic energy is transmitted into a liquid sample by means of the walls of the vessel of the ultrasonic bath.

The term "probe-type ultrasonic generator" refers to an ultrasonic probe immersed in a medium for direct ultrasonic treatment. The term "direct sonication" refers to the direct incorporation of ultrasonic waves into the treatment liquid.

The term "ultrasonic flow cell" or "ultrasonic reactor chamber" refers to an apparatus that: with this apparatus, the sonication process can be carried out in flow-through mode. In some embodiments, the ultrasonic flow cell is a single-pass (single-pass) configuration, a multiple-pass (multiple-pass) configuration, or a recirculation configuration.

The term "applying" refers to the act of laying or spreading a substance on a surface.

The term "current collector" refers to any electrically conductive substrate that is in contact with the electrode layer and is used to conduct current to the electrode during discharge or charge of the secondary battery. Some non-limiting examples of current collectors include a single conductive metal layer or substrate and a single conductive metal layer or substrate covered with a conductive coating, such as a carbon black-based coating. The conductive metal layer or substrate may be in the form of a foil or a porous body having a three-dimensional network structure, and may be a polymer or a metallic material or a metallized polymer. In some embodiments, the three-dimensional porous current collector is covered with a conformal carbon layer (conformal carbon layer).

The term "electrode layer" refers to a layer comprising electrochemically active material in contact with a current collector. In some embodiments, the electrode layer is made by applying a coating on the current collector. In some embodiments, the electrode layer is located on a surface of the current collector. In other embodiments, the three-dimensional porous current collector is covered with a conformal electrode layer.

The term "doctor blading" refers to a process for making large area films on rigid or flexible substrates. The coating thickness can be controlled by an adjustable gap width between the blade and the coated side, which allows the deposition of variable wet layer thicknesses.

The term "slot-die coating" refers to a process for producing large area films on rigid or flexible substrates. The slurry is applied to a substrate mounted on a roll and continuously delivered to the nozzle by continuously pumping the slurry through the nozzle onto the substrate. The thickness of the coating is controlled by various methods, such as changing the flow rate of the slurry or the speed of the roll.

The term "room temperature" refers to a room temperature of about 18 ℃ to about 30 ℃, such as 18 ℃, 19 ℃,20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃. In some embodiments, room temperature refers to a temperature of about 20 ℃ +/-1 ℃ or +/-2 ℃ or +/-3 ℃. In other embodiments, room temperature refers to a temperature of about 22 ℃ or about 25 ℃.

The term "average particle diameter D50" refers to the cumulative 50% size on a volume basis (D50), which is the particle diameter at the point of 50% on the cumulative curve when the cumulative curve is plotted (i.e., the particle diameter at the 50 th percentile (median) of the particle volume), such that a particle size distribution is obtained on a volume basis and the total volume is 100%. In addition, regarding the cathode active material of the present invention, the particle diameter D50 refers to the volume average particle diameter of secondary particles formed by mutual agglomeration of primary particles, and in the case where the particles are composed of only primary particles, the average particle diameter refers to the volume average particle diameter of primary particles.

The term "solids content" refers to the amount of non-volatile material remaining after evaporation.

The term "peel strength" refers to the amount of force required to separate two materials (e.g., current collector and electrode active material coating) that are adhered to each other. It is a measure of the strength of the bond between these two materials, usually expressed in N/cm.

The term "C-rate" refers to the charge rate or discharge rate of a battery in terms of its total storage capacity, expressed as Ah or mAh. For example, a rate of 1C means that all stored energy is utilized within one hour; 0.1C means that 10% of the energy is utilized within one hour or the entire energy is utilized within 10 hours; and 5C means that the full energy is utilized within 12 minutes.

The term "ampere-hour (Ah)" refers to a unit used in explaining the storage capacity of a battery. For example, a 1Ah capacity battery may provide 1 amp of current for 1 hour or 0.5 amps for two hours, etc. Thus, 1 ampere-hour (Ah) corresponds to 3,600 coulombs of charge. Similarly, the term "milliamp hour (mAh)" also refers to the unit used in the storage capacity of the battery and is 1/1,000 amp hours.

The term "battery cycle life" refers to the number of full charge/discharge cycles that a battery can perform before its rated capacity drops below 80% of its initial rated capacity.

The term "capacity" refers to a characteristic of an electrochemical cell and refers to the total amount of charge that an electrochemical cell (e.g., battery) is capable of retaining. Capacity is typically expressed in ampere-hours. The term "specific capacity" refers to the capacity output per unit weight of an electrochemical cell (e.g., battery), typically expressed as Ah/kg or mAh/g.

In the following description, all numbers disclosed herein are approximate values, regardless of whether the word "about" or "approximately" is used in conjunction. They may vary by 1%, 2%, 5% or sometimes 10% to 20%. Whenever disclosed having a lower limit R^LAnd an upper limit R^UTo the extent that any numerical range recited herein is intended, any numerical value falling within the range is specifically disclosed. Specifically, the following values within this range are specifically disclosed: r ═ R^L+k*(R^U-R^L) Where k is a variable from 0% to 100%. Also, any numerical range defined by two R numbers as defined above is also specifically disclosed.

Generally, lithium ion battery electrodes are manufactured by casting an organic slurry onto a metallic current collector. The slurry comprises an electrode active material, conductive carbon and a binder in an organic solvent, most commonly N-methyl-2-pyrrolidone (NMP). As the binder, polyvinylidene fluoride (PVDF), which is the most common, is dissolved in a solvent, and a conductive additive and an electrode active material are suspended in a slurry. PVDF provides good electrochemical stability and high adhesion for electrode materials and current collectors. However, PVDF can only be dissolved in some specific organic solvents, such as flammable and toxic N-methyl-2-pyrrolidone (NMP), requiring specific handling.

During the drying process, an NMP recovery system must be used to recover the NMP vapor. Since this requires a large capital investment, a significant cost is incurred in the manufacturing process. It is preferred to use an inexpensive and environmentally friendly solvent, such as an aqueous solvent, as this can reduce the capital intensive overhead of the recovery system. Attempts to use water-based coating processes instead of organic NMP-containing coating processes have been successfully used for the negative electrode. A typical water-based slurry for anodic coating contains carboxymethyl cellulose (CMC) and Styrene Butadiene Rubber (SBR). Within the cell, the cathode is at a high voltage. Most rubbers, including SBR, are stable only at low voltage of the anode and decompose at high voltage. Thus, in contrast to anodes, it is much more difficult to prepare water-based coatings for cathodes.

Another concern with using aqueous processes is that many cathode active materials are not inert in water, which can cause problems and complicate the aqueous coating process of the cathode. Lithium in the cathode active material may react with H₂The O reaction generates LiOH, resulting in a decrease in electrochemical performance. Generally, the surface of the cathode active material is coated with an ion-conductive solid compound to improve its stability and compatibility with an aqueous process. The pH of the slurry may be adjusted by adding an acid to the solution to neutralize the alkali on the surface of the cathode active material. However, when exposed to water, a large amount of the soluble alkali LiOH continues to be formed, thereby damaging the cathode active material at an extremely high rate.

Accordingly, the present invention provides a method of preparing a cathode using an aqueous slurry. Fig. 1 shows a flow diagram of one embodiment of the steps of a method 100 of making a cathode. The slurry prepared by the method disclosed herein exhibits improved stability by reducing the reaction of the cathode active material and water, thereby improving battery performance.

In general, nickel-rich NMC materials can react with water during electrode preparation, resulting in metal leaching, which can lead to structural changes and performance degradation. When the NMC material is mixed with water, delithiated surface regions can form rapidly within minutes, and surface impurities (e.g., LiOH) formed in the delithiated surface regions can lead to a significant capacity reduction. However, the addition of additional amounts of LiOH or other lithium compounds in the concentrations described herein has the unexpected effect of improving the capacity and electrochemical performance of cathodes formed therefrom.

In some embodiments, the first suspension is formed by dispersing the binder material in water in step 101. In other embodiments, the first suspension further comprises a conductive agent dispersed in water.

In certain embodiments, the binder material is Styrene Butadiene Rubber (SBR), carboxymethylcellulose (CMC), acrylonitrile copolymer, polyacrylic acid (PAA), Polyacrylonitrile (PAN), Polyacrylamide (PAM), LA132, LA133, LA138, latex, alginate, polyvinylidene fluoride (PVDF), poly (vinylidene fluoride) -hexafluoropropylene (PVDF-HFP), Polytetrafluoroethylene (PTFE), polystyrene, polyvinyl alcohol (PVA), polyvinyl acetate, polyisoprene, polyaniline, polyethylene, polyimide, polyurethane, polyvinyl butyral, polyvinyl pyrrolidone (PVP), gelatin, chitosan, starch, agar, xanthan gum, gellan gum, guar gum arabic, caraya gum (gum karaya), tara gum (tagura m), tragacanth gum, casein, amylose, pectin, PEDOT: PSS, carrageenan, and combinations thereof. In certain embodiments, the alginate comprises a material selected from the group consisting of Na, Li, K, Ca, NH₄A cation of Mg, Al, or a combination thereof. In certain embodiments, the binder material is free of styrene butadiene rubber, carboxymethylcellulose, acrylonitrile copolymers, polyacrylic acid, polyacrylonitrile, LA132, LA133, LA138, TRD202A, latex, alginate, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polystyrene, polyvinyl alcohol, polyvinyl acetate, polyisoprene, polyaniline, polyethylene, polyimide, polyurethane, polyvinyl butyral, polyvinyl pyrrolidone, gelatin, chitosan, starch, agar, xanthan gum, gum arabic, gellan gum, guar gum, caraya gum (gum karaya), tara gum (tara gum), tragacanth gum, casein, amylose, pectin, or carrageenan. In certain embodiments, the adhesiveThe binder material is not a fluoropolymer such as PVDF, PVDF-HFP, or PTFE.

In some embodiments, the binder material is a polymer comprising one or more functional groups comprising halogen, O, N, S, or a combination thereof. Some non-limiting examples of suitable functional groups include alkoxy, aryloxy, nitro, thiol, thioether, imine, cyano, amide, amine (primary, secondary, or tertiary), carboxyl, ketone, aldehyde, ester, hydroxyl, and combinations thereof. In some embodiments, the functional group is or includes an alkoxy group, an aryloxy group, a carboxyl group (i.e., -COOH), a nitrile, -CO₂CH₃、-CONH₂、-OCH₂CONH₂or-NH₂。

In certain embodiments, the binder material is a polymer comprising one or more selectively substituted monomers selected from the group consisting of: vinyl ethers, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, acrylic acid, methacrylic acid, acrylates, methacrylates, 2-hydroxyethyl acrylate, and combinations thereof.

In some embodiments, the adhesive materials disclosed herein are derived from at least one olefin monomer and at least one monomer comprising a functional group selected from the group consisting of amine groups, cyano groups, carboxyl groups, and combinations thereof. By olefin is meant an unsaturated hydrocarbon-based compound containing at least one carbon-carbon double bond. In certain embodiments, the olefin is a conjugated diene. Some non-limiting examples of suitable olefins include C containing ethylenic unsaturation_2-20Aliphatic Compounds and C_8-20Aromatic compounds, and cyclic compounds such as cyclobutene, cyclopentene, dicyclopentadiene, and norbornene. Some non-limiting examples of suitable olefin monomers include styrene, ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4, 6-dimethyl-1-heptene, 4-vinylcyclohexene, vinylcyclohexane, norbornadiene, ethylidene norbornene, cyclopentene, cyclohexene, dicyclopentadieneCyclooctene, C_4-40Dienes and combinations thereof. In certain embodiments, the olefin monomer is propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or combinations thereof. In some embodiments, C_4-40Diolefins include, but are not limited to, 1, 3-butadiene, 1, 3-pentadiene, 1, 4-hexadiene, 1, 5-hexadiene, 1, 7-octadiene, 1, 9-decadiene, isoprene, myrcene, and combinations thereof.

In certain embodiments, the binder materials disclosed herein are derived from at least two vinyl monomers selected from the group consisting of styrene, substituted styrenes, vinyl halides, vinyl ethers, vinyl acetate, vinyl pyridine, vinylidene fluoride, acrylonitrile, acrylic acid, acrylates, methacrylic acid, methacrylates, acrylamides, methacrylamides, and combinations thereof. In certain embodiments, the binder materials disclosed herein are derived from acrylonitrile or methacrylonitrile, and acrylic or methacrylic acid. In certain embodiments, the binder materials disclosed herein are derived from acrylonitrile or methacrylonitrile, and acrylamide or methacrylamide. In certain embodiments, the binder materials disclosed herein are derived from acrylonitrile or methacrylonitrile, and acrylic or methacrylic acid, and acrylamide or methacrylamide. In some embodiments, the binder materials disclosed herein are derived from acrylonitrile or methacrylonitrile, and acrylic acid or methacrylic acid, and methyl acrylate or methyl methacrylate, and acrylamide or methacrylamide.

In some embodiments, the binder materials disclosed herein are random interpolymers. In other embodiments, the binder materials disclosed herein are random interpolymers wherein at least two monomeric units are randomly distributed. In some embodiments, the binder material disclosed herein is an alternating interpolymer. In other embodiments, the binder materials disclosed herein are alternating interpolymers wherein at least two monomeric units are alternately distributed. In certain embodiments, the binder material is a block interpolymer.

In certain embodiments, the conductive agent is a carbonaceous material selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In certain embodiments, the conductive agent does not comprise a carbonaceous material.

In some embodiments, the conductive agent is a conductive polymer selected from the group consisting of polypyrrole, polyaniline, polyacetylene, polyphenylene sulfide (PPS), poly-p-styrene (PPV), poly (3, 4-ethylenedioxythiophene) (PEDOT), polythiophene, and combinations thereof. In some embodiments, the conductive agent plays both roles, acting not only as a conductive agent but also as a binder. In certain embodiments, the positive electrode layer includes two components, a cathode active material and a conductive polymer. In other embodiments, the positive electrode layer includes a cathode active material, a conductive agent, and a conductive polymer. In certain embodiments, the conductive polymer is an additive, and the positive electrode layer includes a cathode active material, a conductive agent, a binder, and a conductive polymer. In other embodiments, the positive electrode layer does not contain a conductive polymer.

In certain embodiments, the amount of each of the binder material and the conductive material in the first suspension is independently about 1% to about 50%, about 1% to about 40%, about 1% to about 30%, about 1% to about 20%, about 1% to about 15%, about 1% to about 10%, about 1% to about 5%, about 3% to about 20%, about 5% to about 10%, about 10% to about 20%, about 10% to about 15%, or about 15% to about 20% by weight, based on the total weight of the first suspension. In some embodiments, the amount of each of the binder material and the conductive material in the first suspension is independently less than 20%, less than 15%, less than 10%, less than 8%, or less than 6% by weight, based on the total weight of the first suspension.

In some embodiments, the solids content of the first suspension is about 10% to about 40%, about 10% to about 35%, about 10% to about 30%, about 10% to about 25%, about 10% to about 20%, about 10% to about 18%, about 12% to about 25%, about 12% to about 20%, about 12% to about 18%, about 15% to about 25%, about 15% to about 20%, or about 18% to about 25% by weight, based on the total weight of the first suspension. In certain embodiments, the solids content of the first suspension is about 10%, about 12%, about 15%, about 18%, about 20%, or about 25% by weight, based on the total weight of the first suspension. In certain embodiments, the solids content of the first suspension is at least 10%, at least 12%, at least 15%, at least 18%, or at least 20% by weight, based on the total weight of the first suspension. In certain embodiments, the solids content of the first suspension is less than 25%, less than 20%, less than 18%, or less than 15% by weight, based on the total weight of the first suspension.

In certain embodiments, the first suspension is mixed at a temperature of from about 10 ℃ to about 40 ℃, from about 10 ℃ to about 35 ℃, from about 10 ℃ to about 30 ℃, from about 10 ℃ to about 25 ℃, from about 10 ℃ to about 20 ℃, or from about 10 ℃ to about 15 ℃. In some embodiments, the first suspension is mixed at a temperature of less than 40 ℃, less than 35 ℃, less than 30 ℃, less than 25 ℃, less than 20 ℃, less than 15 ℃ or less than 10 ℃. In some embodiments, the first suspension is mixed at a temperature of about 40 ℃, about 35 ℃, about 30 ℃, about 25 ℃, about 20 ℃, about 15 ℃, or about 10 ℃.

In some embodiments, the aqueous solution of the lithium-containing compound is prepared by dissolving the lithium compound in water. In step 102, a second suspension is formed by adding an aqueous solution of a lithium-containing compound to the first suspension.

In certain embodiments, the lithium compound is selected from the group consisting of lithium borate, lithium bromide, lithium chloride, lithium bicarbonate, lithium hydroxide, lithium iodide, lithium nitrate, lithium sulfate, lithium acetate, lithium lactate, lithium citrate, lithium succinate, and combinations thereof.

The second suspension is formed by adding an aqueous solution comprising a lithium compound to the first suspension. It was found that the second suspension should be stirred for less than about 1 hour, since stirring times of more than 60 minutes may damage the binder or the conductive agent. In some embodiments, the second suspension is stirred for about 1 minute to about 60 minutes, about 1 minute to about 50 minutes, about 1 minute to about 40 minutes, about 1 minute to about 30 minutes, about 1 minute to about 20 minutes, about 1 minute to about 10 minutes, about 5 minutes to about 60 minutes, about 5 minutes to about 50 minutes, about 5 minutes to about 40 minutes, about 5 minutes to about 30 minutes, about 5 minutes to about 20 minutes, about 5 minutes to about 10 minutes, a period of about 10 minutes to about 60 minutes, about 10 minutes to about 50 minutes, about 10 minutes to about 40 minutes, about 10 minutes to about 30 minutes, about 10 minutes to about 20 minutes, about 15 minutes to about 60 minutes, about 15 minutes to about 50 minutes, about 15 minutes to about 40 minutes, about 15 minutes to about 30 minutes, about 15 minutes to about 20 minutes, about 20 minutes to about 50 minutes, about 20 minutes to about 40 minutes, or about 20 minutes to about 30 minutes.

In certain embodiments, the second suspension is stirred for a period of less than 60 minutes, less than 55 minutes, less than 50 minutes, less than 45 minutes, less than 40 minutes, less than 35 minutes, less than 30 minutes, less than 25 minutes, less than 20 minutes, less than 15 minutes, less than 10 minutes, or less than 5 minutes. In some embodiments, the second suspension is stirred for a period of time of greater than about 55 minutes, greater than about 50 minutes, greater than about 45 minutes, greater than about 40 minutes, greater than about 35 minutes, greater than about 30 minutes, greater than about 25 minutes, greater than about 20 minutes, greater than about 15 minutes, greater than about 10 minutes, or greater than about 5 minutes.

In some embodiments, the second suspension is stirred at a temperature in the range of about 5 ℃ to about 35 ℃, about 5 ℃ to about 30 ℃, about 5 ℃ to about 25 ℃, about 5 ℃ to about 20 ℃, about 5 ℃ to about 15 ℃, or about 5 ℃ to about 10 ℃. In certain embodiments, the second suspension is stirred at a temperature of less than 35 ℃, less than 30 ℃, less than 25 ℃, less than 20 ℃, less than 15 ℃ or less than 10 ℃. In some embodiments, the second suspension is stirred at a temperature greater than about 25 ℃, greater than about 20 ℃, greater than about 15 ℃, greater than about 10 ℃, or greater than about 5 ℃.

Lithium ions (Li) in the second suspension⁺) Is critical to the effect of cell performance. In some embodiments, Li in the second suspension⁺The concentration is about 0.0005M to 0.5M or about 0.001M to 0.5M. In certain embodiments, Li in the second suspension⁺Concentrations of about 0.001M to about 0.4M, about 0.001M to about 0.3M, about 0.001M to about 0.25M, about 0.001M to about 0.2M, about 0.001M to about 0.15M, about 0.001M to about 0.1M, about 0.001M to about 0.05M, about 0.001M to about 0.01M, about 0.005M to about 0.5M, about 0.005M to about 0.4M, about 0.005M to about 0.35M, about 0.005M to about 0.3M, about 0.005M to about 0.25M, about 0.005M to about 0.2M, about 0.005M to about 0.15M, about 0.005M to about 0.1M, or about 0.005M to about 0.05M. In some embodiments, Li in the second suspension⁺The concentration is less than about 0.5M, less than about 0.4M, less than about 0.35M, less than about 0.3M, less than about 0.25M, less than about 0.2M, less than about 0.15M, or less than about 0.1M. In some embodiments, Li in the second suspension⁺Concentrations greater than about 0.001M, greater than about 0.005M, greater than about 0.01M, greater than about 0.05M, greater than about 0.1M, greater than about 0.15M, or greater than about 0.2M.

In a conventional method of preparing a cathode slurry, an organic compound, such as NMP, is generally used as a solvent. However, the use of organic solvents causes serious environmental problems. One of the advantages of the present invention is that it prepares the cathode slurry by an aqueous process using water as a solvent. A lithium compound is added to the slurry to stabilize the cathode active material in the aqueous slurry. Therefore, it is necessary that the lithium compound be soluble in water. In some embodiments, the lithium compound has a solubility in water of about 1g/100ml to about 200g/100ml, about 1g/100ml to about 180g/100ml, about 1g/100ml to about 160g/100ml, about 1g/100ml to about 140g/100ml, about 1g/100ml to about 120g/100ml, about 1g/100ml to about 100g/100ml, about 1g/100ml to about 90g/100ml, about 1g/100ml to about 80g/100ml, about 1g/100ml to about 70g/100ml, about 1g/100ml to about 60g/100ml, about 1g/100ml to about 50g/100ml, about 1g/100ml to about 40g/100ml, about 1g/100ml to about 30g/100ml, at 20 ℃ From about 1g/100ml to about 20g/100ml, from about 1g/100ml to about 10g/100ml, from about 20g/100ml to about 100g/100ml, from about 20g/100ml to about 80g/100ml, from about 20g/100ml to about 60g/100ml, from about 20g/100ml to about 40g/100ml, from about 20g/100ml to about 30g/100ml, from about 40g/100ml to about 100g/100ml, from about 40g/100ml to about 80g/100ml, from about 40g/100ml to about 60g/100ml, from about 60g/100ml to about 100g/100ml, from about 60g/100ml to about 80g/100ml, from about 100g/100ml to about 200g/100ml, from about 100g/100ml to about 180g/100ml, or from about 120g/100ml to about 180g/100 ml. In some embodiments, the solubility of the lithium compound in water is less than 200g/100ml, less than 180g/100ml, less than 160g/100ml, less than 140g/100ml, less than 120g/100ml, less than 100g/100ml, less than 80g/100ml, less than 60g/100ml, less than 40g/100ml, or less than 20g/100ml at 20 ℃. In some embodiments, the solubility of the lithium compound in water should be greater than about 1g/100ml, greater than about 10g/100ml, greater than about 20g/100ml, greater than about 30g/100ml, greater than about 40g/100ml, greater than about 50g/100ml, greater than about 60g/100ml, greater than about 70g/100ml, greater than about 80g/100ml, greater than about 90g/100ml, greater than about 100g/100ml, greater than about 120g/100ml, or greater than about 140g/100ml at 20 ℃.

In some embodiments, in step 103, a third suspension is formed by dispersing the cathode active material in a second suspension comprising a binder, a conductive agent, and at least one lithium compound.

In some embodiments, the active battery electrode material is a cathode active material, wherein the cathode active material is selected from the group consisting of LiCoO₂、LiNiO₂、LiNi_xMn_yO₂、Li_1+zNi_xMn_yCo_1-x-yO₂、LiNi_xCo_yAl_zO₂、LiV₂O₅、LiTiS₂、LiMoS₂、LiMnO₂、LiCrO₂、LiMn₂O₄、Li₂MnO₃、LiFeO₂、LiFePO₄And combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. In certain embodiments, the cathode active material is selected from the group consisting of LiCoO₂、LiNiO₂、LiNi_xMn_yO₂、Li_1+zNi_xMn_yCo_1-x-yO₂(NMC)、LiNi_xCo_yAl_zO₂、LiV₂O₅、LiTiS₂、LiMoS₂、LiMnO₂、LiCrO₂、LiMn₂O₄、LiFeO₂、LiFePO₄And combinations thereof, wherein each x is independently 0.4 to 0.6;each y is independently 0.2 to 0.4; and each z is independently 0 to 0.1. In other embodiments, the cathode active material is not LiCoO₂、LiNiO₂、LiV₂O₅、LiTiS₂、LiMoS₂、LiMnO₂、LiCrO₂、LiMn₂O₄、LiFeO₂Or LiFePO₄. In a further embodiment, the cathode active material is not LiNi_xMn_yO₂、Li_{1+ z}Ni_xMn_yCo_1-x-yO₂Or LiNi_xCo_yAl_zO₂Wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. In certain embodiments, the cathode active material is Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂(ii) a Wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c ≦ 1. In some embodiments, the cathode active material has the general formula Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂Wherein a is more than or equal to 0.33 and less than or equal to 0.92, a is more than or equal to 0.33 and less than or equal to 0.9, a is more than or equal to 0.33 and less than or equal to 0.8, a is more than or equal to 0.5 and less than or equal to 0.92, a is more than or equal to 0.5 and less than or equal to 0.9, a is more than or equal to 0.5 and less than or equal to 0.8, a is more than or equal to 0.6 and less; b is more than or equal to 0 and less than or equal to 0.5, b is more than or equal to 0 and less than or equal to 0.3, b is more than or equal to 0.1 and less than or equal to 0.5, b is more than or equal to 0.1 and less than or equal to 0.4, b is more than or equal to 0.1 and less than or equal to 0.3, b is more than or equal to 0.1 and less than or equal to 0.2 or b; c is more than or equal to 0 and less than or equal to 0.5, c is more than or equal to 0 and less than or equal to 0.3, c is more than or equal to 0.1 and less than or equal to 0.5, c is more than or equal to 0.1 and less than or equal to 0.4, c is more than or equal to 0.1 and less than or equal to 0.3, c is more than or equal to 0.1 and less than or equal to 0.2 or c.

In certain embodiments, the cathode active material is doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In some embodiments, the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si, or Ge. In certain embodiments, the dopant is not Al, Sn, or Zr.

The methods disclosed herein are particularly suitable for preparing cathodes using nickel-containing cathode active materials. Nickel-containing cathodes prepared by the methods disclosed herein exhibit improved electrochemical performance and long-term stability.

In some embodiments, the cathode active material is LiNi_0.33Mn_0.33Co_0.33O₂(NMC333)、LiNi_0.4Mn_0.4Co_0.2O₂、LiNi_0.5Mn_0.3Co_0.2O₂(NMC532)、LiNi_0.6Mn_0.2Co_0.2O₂(NMC622)、LiNi_0.7Mn_0.15Co_0.15O₂、LiNi_0.8Mn_0.1Co_0.1O₂(NMC811)、LiNi_0.92Mn_0.04Co_0.04O₂、LiNi_0.8Co_0.15Al_0.05O₂(NCA)、LiNiO₂(LNO) and combinations thereof.

In other embodiments, the cathode active material is not LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄Or Li₂MnO₃. In a further embodiment, the cathode active material is not LiNi_0.33Mn_0.33Co_0.33O₂、LiNi_0.4Mn_0.4Co_0.2O₂、LiNi_0.5Mn_0.3Co_0.2O₂、LiNi_0.6Mn_0.2Co_0.2O₂、LiNi_0.7Mn_0.15Co_0.15O₂、LiNi_0.8Mn_0.1Co_0.1O₂、LiNi_0.92Mn_0.04Co_0.04O₂Or LiNi_0.8Co_0.15Al_0.05O₂。

In certain embodiments, the cathode active material comprises or is itself a core-shell composite having a core structure and a shell structure, wherein the core and the shell each independently comprise a lithium transition metal oxide selected from the group consisting of Li_{1+ x}Ni_aMn_bCo_cAl_(1-a-b-c)O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃、LiCrO₂、Li₄Ti₅O₁₂、LiV₂O₅、LiTiS₂、LiMoS₂And combinations thereof, wherein-0.2. ltoreq. x.ltoreq.0.2, 0. ltoreq. a<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1. In other embodiments, the core and the shell each independently comprise two or more lithium transition metal oxides. In some embodiments, one of the core or shell comprises only one lithium transition metal oxide, while the other comprises two or more lithium transition metal oxides. The lithium transition metal oxides in the core and shell may be the same or different or partially different. In some embodiments, two or more lithium transition metal oxides are uniformly distributed in the core. In certain embodiments, the two or more lithium transition metal oxides are not uniformly distributed in the core. In some embodiments, the cathode active material is not a core-shell composite.

In some embodiments, the lithium transition metal oxide in the core and the shell are each independently doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In certain embodiments, the core and the shell each independently comprise two or more doped lithium transition metal oxides. In some embodiments, the two or more doped lithium transition metal oxides are uniformly distributed on the core and/or the shell. In certain embodiments, the two or more doped lithium transition metal oxides are non-uniformly distributed on the core and/or the shell.

In some embodiments, the cathode active material comprises, or is itself, a core-shell composite comprising a core comprising a lithium transition metal oxide and a shell comprising a transition metal oxide. In certain embodiments, the lithium transition metal oxide is selected from the group consisting of Li_1+xNi_aMn_bCo_cAl_(1-a-b-c)O₂、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li₂MnO₃、LiCrO₂、Li₄Ti₅O₁₂、LiV₂O₅、LiTiS₂、LiMoS₂And combinations thereof; wherein x is more than or equal to-0.2 and less than or equal to 0.2, and a is more than or equal to 0<1、0≤b<1、0≤c<1 and a + b + c is less than or equal to 1. In some embodimentsWherein the transition metal oxide is selected from Fe₂O₃、MnO₂、Al₂O₃、MgO、ZnO、TiO₂、La₂O₃、CeO₂、SnO₂、ZrO₂、RuO₂And combinations thereof. In certain embodiments, the shell comprises a lithium transition metal oxide and a transition metal oxide.

In some embodiments, the core has a diameter of about 1 μm to about 15 μm, about 3 μm to about 10 μm, about 5 μm to about 45 μm, about 5 μm to about 35 μm, about 5 μm to about 25 μm, about 10 μm to about 45 μm, about 10 μm to about 40 μm, about 10 μm to about 35 μm, about 10 μm to about 25 μm, about 15 μm to about 45 μm, about 15 μm to about 30 μm, about 15 μm to about 25 μm, about 20 μm to about 35 μm, or about 20 μm to about 30 μm. In certain embodiments, the shell has a thickness of about 1 μm to about 45 μm, about 1 μm to about 35 μm, about 1 μm to about 25 μm, about 1 μm to about 15 μm, about 1 μm to about 10 μm, about 1 μm to about 5 μm, about 3 μm to about 15 μm, about 3 μm to about 10 μm, about 5 μm to about 10 μm, about 10 μm to about 35 μm, about 10 μm to about 20 μm, about 15 μm to about 30 μm, about 15 μm to about 25 μm, or about 20 μm to about 35 μm. In certain embodiments, the ratio of the diameter or thickness of the core and shell is in the range of 15:85 to 85:15, 25:75 to 75:25, 30:70 to 70:30, or 40:60 to 60: 40. In certain embodiments, the core and shell are 95:5, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, or 30:70 by volume or weight ratio.

In some embodiments, the binder material and the conductive agent may be mixed in the first suspension prior to adding the aqueous solution containing the lithium compound. This is advantageous because it enables a better dispersion of the material in the second suspension. However, it requires mixing the binder material with the lithium compound before adding the cathode active material. In some embodiments, a binder material, a conductive agent, and a lithium compound may be mixed to form a first suspension. In other embodiments, the binder material and the lithium compound may be mixed to form the first suspension. Thereafter, a second suspension is formed by dispersing the cathode active material and/or the conductive agent in the first suspension. The conductive agent may be added in any process step prior to forming the homogenized slurry.

Since the cathode active material can chemically react with water, it is necessary to add the cathode active material to an aqueous environment containing a lithium compound. In some embodiments, a binder material and a conductive agent may be mixed to form a first suspension. The cathode active material and the aqueous solution including the lithium compound may be mixed to form a second suspension. Thereafter, a third suspension is formed by mixing the first and second suspensions. In other embodiments, the cathode active material and the aqueous solution containing the lithium compound may be mixed to form a first suspension. In some embodiments, the binder material and the conductive agent may be mixed to form a second suspension. Thereafter, a third suspension is formed by mixing the first and second suspensions. In certain embodiments, the binder material and the conductive agent are not separately mixed to form the second suspension, but are added directly to the first suspension, and then homogenized by a homogenizer to obtain a homogenized slurry. When the binder material and the conductive agent are added in order without forming the second suspension, stirring or dispersion may be performed between the addition processes.

In some embodiments, the third suspension is degassed under reduced pressure for a short period of time to remove entrapped gas bubbles in the suspension prior to homogenizing the third suspension. In some embodiments, the second suspension is degassed at a pressure of about 1kPa to about 20kPa, about 1kPa to about 15kPa, about 1kPa to about 10kPa, about 5kPa to about 20kPa, about 5kPa to about 15kPa, or about 10kPa to about 20 kPa. In certain embodiments, the suspension is degassed at a pressure of less than 20kPa, less than 15kPa, or less than 10 kPa. In some embodiments, the suspension is degassed for a period of time from about 30 minutes to about 4 hours, from about 1 hour to about 4 hours, from about 2 hours to about 4 hours, or from about 30 minutes to about 2 hours. In certain embodiments, the second suspension is degassed for a period of less than 4 hours, less than 2 hours, or less than 1 hour.

In certain embodiments, the third suspension is degassed after homogenization. The degassing step may also be carried out before homogenising the third suspension, using the pressure and time conditions specified in the degassing step for the third suspension.

Homogenizing the third suspension by a homogenizer at a temperature of about 10 ℃ to about 30 ℃ to obtain a homogenized slurry. The homogenizer may be equipped with a temperature control system, and the temperature of the third suspension may be controlled by the temperature control system. Any homogenizer that can reduce or eliminate particle aggregation and/or promote uniform distribution of the slurry components can be used herein. The homogeneous distribution plays an important role in manufacturing a battery having good battery performance. In some embodiments, the homogenizer is a planetary mixer, a stirred mixer, a stirrer, or an sonicator.

In some embodiments, homogenizing the third suspension is performed at a temperature of about 10 ℃ to about 30 ℃, about 10 ℃ to about 25 ℃, about 10 ℃ to about 20 ℃, or about 10 ℃ to about 15 ℃. In some embodiments, homogenizing the third suspension is performed at a temperature of less than 30 ℃, less than 25 ℃, less than 20 ℃, or less than 15 ℃.

In some embodiments, the planetary mixing mixer comprises at least one planetary paddle and at least one high speed dispersing paddle. In certain embodiments, the rotation speed of the planetary paddles is about 20rpm to about 200rpm, about 20rpm to about 150rpm, about 30rpm to about 150rpm, or about 50rpm to about 100 rpm. In certain embodiments, the rotation speed of the dispersing paddles is about 1,000rpm to about 4,000rpm, about 1,000rpm to about 3,500rpm, about 1,000rpm to about 3,000rpm, about 1,000rpm to about 2,000rpm, about 1,500rpm to about 3,000rpm, or about 1,500rpm to about 2,500 rpm.

In certain embodiments, the sonicator is an ultrasonic bath, a probe-type sonicator, or an ultrasonic flow cell. In some embodiments, the ultrasonic generator operates at a power density of about 10W/L to about 100W/L, about 20W/L to about 100W/L, about 30W/L to about 100W/L, about 40W/L to about 80W/L, about 40W/L to about 70W/L, about 40W/L to about 60W/L, about 40W/L to about 50W/L, about 50W/L to about 60W/L, about 20W/L to about 80W/L, about 20W/L to about 60W/L, or about 20W/L to about 40W/L. In certain embodiments, the ultrasonic generator operates at a power density of about 10W/L, about 20W/L, about 30W/L, about 40W/L, about 50W/L, about 60W/L, about 70W/L, about 80W/L, about 90W/L, or about 100W/L.

When the cathode active material is homogenized in the aqueous slurry for a long time, water may damage the cathode active material even if the lithium compound is present in the third suspension. In some embodiments, the third suspension is homogenized for a period of about 10 minutes to about 6 hours, about 10 minutes to about 5 hours, about 10 minutes to about 4 hours, about 10 minutes to about 3 hours, about 10 minutes to about 2 hours, about 10 minutes to about 1 hour, about 10 minutes to about 30 minutes, about 30 minutes to about 3 hours, about 30 minutes to about 2 hours, about 30 minutes to about 1 hour, about 1 hour to about 6 hours, about 1 hour to about 5 hours, about 1 hour to about 4 hours, about 1 hour to about 3 hours, about 1 hour to about 2 hours, about 2 hours to about 6 hours, about 2 hours to about 4 hours, about 2 hours to about 3 hours, about 3 hours to about 5 hours, or about 4 hours to about 6 hours. In certain embodiments, the third suspension is homogenized for a period of less than 6 hours, less than 5 hours, less than 4 hours, less than 3 hours, less than 2 hours, less than 1 hour, or less than 30 minutes. In some embodiments, the third suspension is homogenized for a period of time greater than about 6 hours, greater than about 5 hours, greater than about 4 hours, greater than about 3 hours, greater than about 2 hours, greater than about 1 hour, greater than about 30 minutes, greater than about 20 minutes, or greater than about 10 minutes.

The most common method of achieving homogeneity is to use high agitation rates, ideally causing turbulence. However, an increase in agitation rate typically results in a large increase in energy requirements, and the stress required to achieve turbulence typically exceeds the capacity of the equipment. In addition, since some cathode active materials are sensitive to shear forces, such stresses may damage the cathode active materials. One advantage of the present invention is that the addition of the lithium compound stabilizes the pH of the slurry, which in turn stabilizes the viscosity of the slurry. This makes it easier to homogenize the slurry and achieve efficient mixing under mild agitation conditions. Another advantage of the present invention is that the time required to mix the components to achieve homogeneity is reduced.

When the pH of the slurry is changed during homogenization or exceeds a certain range, the dispersion uniformity and particle size distribution of water-insoluble components (e.g., electrode active material and conductive agent) in the slurry may be affected, resulting in a decrease in electrode performance. Therefore, it is desirable to maintain a constant pH in the slurry during homogenization.

In some embodiments, the pH of the homogenized slurry is about 8 to about 14, about 8 to about 13.5, about 8 to about 13, about 8 to about 12.5, about 8 to about 12, about 8 to about 11.5, about 8 to about 11, about 8 to about 10.5, about 8 to about 10, about 8 to about 9, about 9 to about 14, about 9 to about 13, about 9 to about 12, about 9 to about 11, about 10 to about 14, about 10 to about 13, about 10 to about 12, about 10 to about 11, about 10.5 to about 14, about 10.5 to about 13.5, about 10.5 to about 13, about 10.5 to about 12.5, about 10.5 to about 12, about 10.5 to about 11.5, about 11 to about 14, about 11 to about 13, about 11 to about 12, about 11.5 to about 12.5, about 11.5 to about 12, or about 12 to about 14. In certain embodiments, the pH of the homogenized slurry is less than 14, less than 13.5, less than 13, less than 12.5, less than 12, less than 11.5, less than 11, less than 10.5, less than 10, less than 9.5, less than 9, less than 8.5, or less than 8. In some embodiments, the pH of the homogenized slurry is about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5, about 12, about 12.5, about 13, about 13.5, or about 14.

In certain embodiments, the amount of conductive agent in the homogenized slurry is about 0.5% to about 5%, about 0.5% to about 3%, about 1% to about 5%, about 1% to about 4%, or about 2% to about 3% by weight, based on the total weight of the homogenized slurry. In some embodiments, the amount of conductive agent in the homogenized slurry is at least about 0.5%, at least about 1%, at least about 2%, at least about 3%, or at least about 4% by weight, based on the total weight of the homogenized slurry. In certain embodiments, the amount of conductive agent in the homogenized slurry is at most about 1%, at most about 2%, at most about 3%, at most about 4%, or at most about 5% by weight, based on the total weight of the homogenized slurry.

In certain embodiments, the amount of binder material in the homogenized slurry is about 1% to about 15%, about 1% to about 10%, about 1% to about 5%, about 3% to about 15%, about 5% to about 10%, or about 10% to about 15% by weight, based on the total weight of the homogenized slurry. In some embodiments, the amount of binder material in the homogenized slurry is less than 15%, less than 10%, less than 8%, or less than 6% by weight, based on the total weight of the homogenized slurry.

In some embodiments, the weight of the binder material is greater than, less than, or equal to the weight of the conductive agent in the homogenized slurry. In certain embodiments, the weight ratio of binder material to conductive agent is about 1:10 to about 10:1, about 1:10 to about 5:1, about 1:10 to about 1:5, about 1:5 to about 5:1, about 1:3 to about 3:1, about 1:2 to about 2:1, or about 1:1.5 to about 1.5: 1.

In certain embodiments, the content of cathode active material in the homogenized slurry is at least 20%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, or at least 60% by weight, based on the total weight of the homogenized slurry. In some embodiments, the content of cathode active material in the homogenized slurry is at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, or at most 75% by weight, based on the total weight of the homogenized slurry.

In some embodiments, the content of cathode active material in the homogenized slurry is about 20% to about 70%, about 20% to about 65%, about 20% to about 60%, about 20% to about 55%, about 20% to about 50%, about 20% to about 40%, about 20% to about 30%, about 30% to about 70%, about 30% to about 65%, about 30% to about 60%, about 30% to about 55%, about 30% to about 50%, about 40% to about 70%, about 40% to about 65%, about 40% to about 60%, about 40% to about 55%, about 40% to about 50%, about 50% to about 70%, or about 50% to about 60% by weight, based on the total weight of the homogenized slurry. In certain embodiments, the content of cathode active material in the homogenized slurry is about 20%, about 30%, about 45%, about 50%, about 65%, or about 70% by weight, based on the total weight of the homogenized slurry.

In some embodiments, the solids content of the homogenized slurry is about 40% to about 80%, about 45% to about 75%, about 45% to about 70%, about 45% to about 65%, about 45% to about 60%, about 45% to about 55%, about 45% to about 50%, about 50% to about 75%, about 50% to about 70%, about 50% to about 65%, about 55% to about 75%, about 55% to about 70%, about 60% to about 75%, or about 65% to about 75% by weight, based on the total weight of the homogenized slurry. In certain embodiments, the solids content of the homogenized slurry is about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, or about 80% by weight, based on the total weight of the homogenized slurry. In certain embodiments, the solids content of the homogenized slurry is at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, or at least 70% by weight, based on the total weight of the homogenized slurry. In certain embodiments, the solids content of the homogenized slurry is less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, or less than 50% by weight, based on the total weight of the homogenized slurry.

The homogenized slurry of the invention may have a higher solids content than conventional cathode slurries. This makes it possible to process more cathode active materials at a time, thereby improving efficiency and maximizing productivity.

The solvent used in the homogenized slurry disclosed herein may comprise at least one alcohol. The addition of alcohol can improve the workability of the slurry and lower the freezing point of water. Some non-limiting examples of suitable alcohols include ethanol, isopropanol, n-propanol, tert-butanol, n-butanol, and combinations thereof. The total amount of alcohol may range from about 1% to about 30%, about 1% to about 20%, about 1% to about 10%, about 1% to about 5%, about 1% to about 3%, about 3% to about 30%, about 3% to about 20%, about 3% to about 10%, about 5% to about 20%, about 5% to about 15%, about 5% to about 10%, or about 8% to about 15% by weight, based on the total weight of the homogenized slurry. In some embodiments, the slurry does not comprise an alcohol.

The viscosity of the homogenized slurry is preferably below about 8,000 mPa-s. In some embodiments, the homogenized slurry has a viscosity of from about 1,000 to about 8,000 mPa-s, from about 1,000 to about 7,000 mPa-s, from about 1,000 to about 6,000 mPa-s, from about 1,000 to about 5,000 mPa-s, from about 1,000 to about 4,000 mPa-s, from about 1,000 to about 3,000 mPa-s, or from about 1,000 to about 2,000 mPa-s. In certain embodiments, the homogenized slurry has a viscosity of less than 8,000 mPa-s, less than 7,000 mPa-s, less than 6,000 mPa-s, less than 5,000 mPa-s, less than 4,000 mPa-s, less than 3,000 mPa-s, or less than 2,000 mPa-s. In some embodiments, the viscosity of the homogenized slurry is about 1,000 mPa-s, about 2,000 mPa-s, about 3,000 mPa-s, about 4,000 mPa-s, about 5,000 mPa-s, about 6,000 mPa-s, about 7,000 mPa-s, or about 8,000 mPa-s. Thus, the resulting slurry can be thoroughly mixed or homogenized.

At alkaline pH, the surface chemistry of the cathode active material may change, thereby affecting the dispersion uniformity and particle size distribution of the electrode components (e.g., cathode active material and conductive agent) in the cathode slurry.

The cathode slurry disclosed herein has a small D50, uniform and narrow particle size distribution. Fig. 2 depicts D50 of cathode active material particles in NMP-containing slurry and alkali-treated slurry of the present invention, respectively. It can be seen that the D50 value for the NMP-containing slurry was large and exhibited a wavy state, while the D50 for the base-treated slurry remained small and constant over time. This indicates that the particles of the alkali-treated slurry of the present invention do not agglomerate or break up over time, and that the slurry can maintain a high and stable degree of dispersion even after prolonged storage. This not only improves the life of the lithium ion battery made therefrom, but also improves the production efficiency because the slurry can be left to stand for a long time for reuse after being made without any fear of any change in the dispersibility of the slurry particles.

The cathode slurry disclosed herein has a small D50, uniform and narrow particle size distribution. In some embodiments, the cathode slurry of the invention has a particle size D50 ranging from about 1 μm to about 15 μm, from about 1 μm to about 12 μm, from about 1 μm to about 10 μm, from about 1 μm to about 8 μm, from about 1 μm to about 6 μm, from about 3 μm to about 15 μm, from about 3 μm to about 12 μm, from about 3 μm to about 10 μm, from about 3 μm to about 8 μm, from about 3 μm to about 6 μm, from about 4 μm to about 15 μm, from about 4 μm to about 12 μm, from about 4 μm to about 10 μm, from about 4 μm to about 8 μm, from about 4 μm to about 6 μm, from about 6 μm to about 15 μm, from about 6 μm to about 12 μm, from about 6 μm to about 10 μm, from about 6 μm to about 8 μm, from about 6 μm to about 15 μm, from about 10 μm to about 10 μm, from about 8 μm to about 8 μm, from about 10 μm to about 10 μm, from about 8 μm to about 10 μm, from about 10 μm to about 10 μm, In the range of about 10 μm to about 12 μm or about 11 μm to about 15 μm. In certain embodiments, the particle size D50 of the cathode active material is less than 15 μm, less than 12 μm, less than 10 μm, less than 8 μm, less than 6 μm, or less than 4 μm. In some embodiments, the particle size D50 of the cathode active material is greater than 1 μm, greater than 3 μm, greater than 4 μm, greater than 6 μm, greater than 8 μm, greater than 10 μm, or greater than 11 μm.

In a conventional method of preparing a cathode slurry, a dispersant may be used to assist dispersion of a cathode active material, a conductive agent, and a binder material in the slurry. Some non-limiting examples of dispersants include polymeric acids and surfactants that can reduce the surface tension between a liquid and a solid. In some embodiments, the dispersant is a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a combination thereof.

One advantage of the present invention is that the components of the slurry can be uniformly dispersed at room temperature without the use of a dispersant. In some embodiments, the method of the present invention does not comprise the step of adding a dispersant to the first suspension, the second suspension, the third suspension, or the homogenized slurry. In certain embodiments, each of the first suspension, the second suspension, the third suspension, and the homogenized slurry is independently free of a dispersant.

Some non-limiting examples of polymeric acids include polylactic acid, polysuccinic acid, polymaleic acid, pyromucic acid, polyfumaric acid, polysorbates, polylinoleic acid, polyglutamic acid, polymethacrylic acid, poly octadeca-9, 11, 13-trien-4-one acid (polymeric acid), polyglycolic acid, polyaspartic acid, polyamic acid, polycarbamic acid, polyacetic acid, polypropionic acid, polybutanoic acid, polysebacic acid, copolymers thereof, and combinations thereof. In certain embodiments, the homogenized slurry is free of polymeric acid.

Some non-limiting examples of suitable nonionic surfactants include carboxylic acid esters, polyethylene glycol esters, and combinations thereof. In some embodiments, the homogenized slurry is free of nonionic surfactants.

Some non-limiting examples of suitable anionic surfactants include alkyl sulfates, alkyl polyethoxylated ether sulfates, alkyl benzene sulfonates, alkyl ether sulfates, sulfonates, sulfosuccinates, sarcosinates, and combinations thereof. In some embodiments, the anionic surfactant comprises a cation selected from the group consisting of sodium, potassium, ammonium, and combinations thereof. In certain embodiments, the anionic surfactant is sodium dodecylbenzene sulfonate, sodium stearate, lithium dodecyl sulfate, or a combination thereof. In some embodiments, the homogenized slurry is free of anionic surfactants.

Some non-limiting examples of suitable cationic surfactants include ammonium salts, phosphonium salts, imidazolium salts, sulfonium salts, and combinations thereof. Some non-limiting examples of suitable ammonium salts include stearyl trimethylammonium bromide (STAB), cetyl trimethylammonium bromide (CTAB), myristyl trimethylammonium bromide (MTAB), trimethylhexadecyl ammonium chloride, and combinations thereof. In some embodiments, the homogenized slurry is free of cationic surfactants.

Some non-limiting examples of suitable amphoteric surfactants are surfactants containing both cationic and anionic groups. The cationic group is ammonium, phosphonium, imidazole, sulfonium, or a combination thereof. The anionic hydrophilic group is a carboxylate, sulfonate, sulfate, phosphate, or a combination thereof. In some embodiments, the homogenized slurry is free of amphoteric surfactants.

After the slurry components are uniformly mixed, the homogenized slurry may be applied to a current collector to form a coating film on the current collector, and then dried in step 104. The current collector serves to collect electrons generated by an electrochemical reaction of the cathode active material or to supply electrons required for the electrochemical reaction. In some embodiments, the current collector may be in the form of a foil, sheet, or film. In certain embodiments, the current collector is stainless steel, titanium, nickel, aluminum, copper, or alloys thereof, or conductive resins. In certain embodiments, the current collector has a two-layer structure including an outer layer and an inner layer, wherein the outer layer comprises a conductive material and the inner layer comprises an insulating material or another conductive material; for example, aluminum covered with a conductive resin layer or a polymer insulating material coated with an aluminum film. In some embodiments, the current collector has a three-layer structure comprising an outer layer, an intermediate layer, and an inner layer, wherein the outer and inner layers comprise a conductive material, and the intermediate layer comprises an insulating material or another conductive material; for example, a plastic substrate coated on both sides with a metal film. In certain embodiments, each of the outer layer, the intermediate layer, and the inner layer is independently stainless steel, titanium, nickel, aluminum, copper, or alloys thereof, or conductive resins. In some embodiments, the insulating material is a polymeric material selected from the group consisting of polycarbonate, polyacrylate, polyacrylonitrile, polyester, polyamide, polystyrene, polyurethane, polyepoxy, poly (acrylonitrile butadiene styrene), polyimide, polyolefin, polyethylene, polypropylene, polyphenylene sulfide, poly (vinyl ester), polyvinyl chloride, polyether, polyphenylene oxide, cellulosic polymers, and combinations thereof. In certain embodiments, the current collector has a three-layer or more structure. In some embodiments, the current collector is coated with a protective coating. In certain embodiments, the protective coating comprises a carbonaceous material. In some embodiments, the current collector is not coated with a protective coating.

In certain embodiments, each of the cathode electrode layer and the anode electrode layer on the current collector independently has a thickness of about 5 μm to about 50 μm, about 5 μm to about 25 μm, about 10 μm to about 90 μm, about 10 μm to about 50 μm, about 10 μm to about 30 μm, about 15 μm to about 90 μm, about 20 μm to about 90 μm, about 25 μm to about 80 μm, about 25 μm to about 75 μm, about 25 μm to about 50 μm, about 30 μm to about 90 μm, about 30 μm to about 80 μm, about 35 μm to about 90 μm, about 35 μm to about 85 μm, about 35 μm to about 80 μm, or about 35 μm to about 75 μm. In some embodiments, the thickness of the electrode layer on the current collector is about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, or about 75 μm.

In some embodiments, a cathode electrode layer and an anode on a current collectorThe areal density of each of the pole electrode layers is independently about 1mg/cm²To about 40mg/cm²About 1mg/cm²To about 35mg/cm²About 1mg/cm²To about 30mg/cm²About 1mg/cm²To about 25mg/cm²About 1mg/cm²To about 15mg/cm²About 3mg/cm²To about 40mg/cm²About 3mg/cm²To about 35mg/cm²About 3mg/cm²To about 30mg/cm²About 3mg/cm²To about 25mg/cm²About 3mg/cm²To about 20mg/cm²About 3mg/cm²To about 15mg/cm²About 5mg/cm²To about 40mg/cm²About 5mg/cm²To about 35mg/cm²About 5mg/cm²To about 30mg/cm²About 5mg/cm²To about 25mg/cm²About 5mg/cm²To about 20mg/cm²About 5mg/cm²To about 15mg/cm²About 8mg/cm²To about 40mg/cm²About 8mg/cm²To about 35mg/cm²About 8mg/cm²To about 30mg/cm²About 8mg/cm²To about 25mg/cm²About 8mg/cm²To about 20mg/cm²About 10mg/cm²To about 40mg/cm²About 10mg/cm²To about 35mg/cm²About 10mg/cm²To about 30mg/cm²About 10mg/cm²To about 25mg/cm²About 10mg/cm²To about 20mg/cm²About 15mg/cm²To about 40mg/cm²Or about 20mg/cm²To about 40mg/cm²。

In some embodiments, an electrically conductive layer may be coated on the aluminum current collector to improve its current conductivity. In certain embodiments, the conductive layer comprises a material selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In some embodiments, the conductive agent is not carbon, carbon black, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, or mesoporous carbon.

In some embodiments, the conductive layer has a thickness of about 0.5 μm to about 5.0 μm. The thickness of the conductive layer will affect the volume occupied by the current collector in the cell and the amount of electrode material, and thus the capacity in the cell.

In certain embodiments, the thickness of the conductive layer on the current collector is from about 0.5 μm to about 4.5 μm, from about 1.0 μm to about 4.0 μm, from about 1.0 μm to about 3.5 μm, from about 1.0 μm to about 3.0 μm, from about 1.0 μm to about 2.5 μm, from about 1.0 μm to about 2.0 μm, from about 1.1 μm to about 2.0 μm, from about 1.2 μm to about 2.0 μm, from about 1.5 μm to about 2.0 μm, from about 1.8 μm to about 2.0 μm, from about 1.0 μm to about 1.8 μm, from about 1.2 μm to about 1.8 μm, from about 1.5 μm to about 1.8 μm, from about 1.0 μm to about 1.5 μm, or from about 1.2 μm to about 1.5 μm. In some embodiments, the thickness of the conductive layer on the current collector is less than 4.5 μm, less than 4.0 μm, less than 3.5 μm, less than 3.0 μm, less than 2.5 μm, less than 2.0 μm, less than 1.8 μm, less than 1.5 μm, or less than 1.2 μm. In some embodiments, the thickness of the conductive layer on the current collector is greater than 1.0 μm, greater than 1.2 μm, greater than 1.5 μm, greater than 1.8 μm, greater than 2.0 μm, greater than 2.5 μm, greater than 3.0 μm, or greater than 3.5 μm.

In addition, the cathode prepared by the present invention shows strong adhesion of the electrode layer to the current collector. It is important that the electrode layer has good peel strength to the current collector, since this can prevent delamination or separation of the electrode, which greatly affects the mechanical stability of the electrode and the cyclability of the battery. Therefore, the electrode should have sufficient peel strength to withstand the stringent requirements of battery manufacture.

Fig. 3 shows bar graphs of peel strength of cathodes coated with an organic slurry, an aqueous slurry comprising untreated cathode active material, and an aqueous slurry prepared according to the present invention, respectively. The figure shows the increase in peel strength of the coating film to the current collector in the electrode prepared by the method disclosed herein.

In some embodiments, the peel strength between the current collector and the electrode layer is from about 1.0N/cm to about 8.0N/cm, from about 1.0N/cm to about 6.0N/cm, from about 1.0N/cm to about 5.0N/cm, from about 1.0N/cm to about 4.0N/cm, from about 1.0N/cm to about 3.0N/cm, from about 1.0N/cm to about 2.5N/cm, from about 1.0N/cm to about 2.0N/cm, from about 1.2N/cm to about 3.0N/cm, from about 1.2N/cm to about 2.5N/cm, from about 1.2N/cm to about 2.0N/cm, from about 1.5N/cm to about 3.0N/cm, from about 1.5N/cm to about 2.5N/cm, from about 1.5N/cm to about 2.0N/cm, from about 1.5N/cm to about 8N/cm, from about 1.0N/cm to about 2 cm, from about 1.0N/cm, from about 2 cm, or from about 1.0N/cm, About 2.0N/cm to about 6.0N/cm, about 2.0N/cm to about 5.0N/cm, about 2.0N/cm to about 3.0N/cm, about 2.0N/cm to about 2.5N/cm, about 2.2N/cm to about 3.0N/cm, about 2.5N/cm to about 3.0N/cm, about 3.0N/cm to about 8.0N/cm, about 3.0N/cm to about 6.0N/cm, or about 4.0N/cm to about 6.0N/cm. In some embodiments, the peel strength between the current collector and the electrode layer is 1.0N/cm or more, 1.2N/cm or more, 1.5N/cm or more, 2.0N/cm or more, 2.2N/cm or more, 2.5N/cm or more, 3.0N/cm or more, 3.5N/cm or more, 4.5N/cm or more, 5.0N/cm or more, 5.5N/cm or more. In some embodiments, the peel strength between the current collector and the electrode layer is less than 6.5.0N/cm, less than 6.0N/cm, less than 5.5N/cm, less than 5.0N/cm, less than 4.5N/cm, less than 4.0N/cm, less than 3.5N/cm, less than 3.0N/cm, less than 2.8N/cm, less than 2.5N/cm, less than 2.2N/cm, less than 2.0N/cm, less than 1.8N/cm, or less than 1.5N/cm.

During the coating process, pH is a very important parameter for controlling the stability of the slurry, since it affects the critical properties of the slurry, such as viscosity and dispersion. These key properties will change if the pH of the slurry changes. The risk of pH instability leads to the need to coat the slurry on the current collector immediately after homogenization. This is difficult to achieve under mass production conditions, as the coating process typically lasts for several hours. Any fluctuations in critical characteristics of the coating process are a serious problem and can make the coating process unstable. One benefit of the present invention is that the pH and key characteristics of the slurry remain stable during and for a long period of time after homogenization. It was found that the pH of the slurries disclosed herein remained relatively constant during extended storage for up to two weeks, while the pH of conventional aqueous slurries increased significantly during storage. The stability of the pH allows the slurries disclosed herein to remain homogeneous and homogeneous during such extended storage, thereby allowing sufficient time for the slurry to be transported for the coating process.

In some embodiments, lithium ions (Li) in the cathode slurry⁺) The concentration is from about 0.0001M to about 1M. In certain embodiments, Li in the cathode slurry⁺A concentration of about 0.0001M to about 0.9M, 0.0001M to about 0.85M, 0.0001M to about 0.8M, 0.0001M to about 0.75M, 0001M to about 0.7M, 0001M to about 0.65M, 0001M to about 0.6M, 0.0001M to about 0.55M, about 0.0001M to about 0.5M, about 0.0001M to about 0.45M, about 0.0001M to about 0.4M, about 0.0001M to about 0.35M, about 0.0001M to about 0.3M, about 0.0001M to about 0.25M, about 0.0001M to about 0.2M, about 0.0001M to about 0.15M, about 0.0001M to about 0.1M, about 0.0001M to about 0.05M, about 0.001M to about 0.01M, about 0.001M to about 0.0.0.001M, about 0.001M to about 0.0.0.0.0.0.001M to about 0.0.0.0.0.0.0.0.0.0.0.001M to about 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.001M to about 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.001M, about 0.0.0.0.0 to about 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.001 to about 0.0.0.0.0.0, About 0.01M to about 0.6M, about 0.01M to about 0.55M, about 0.01M to about 0.5M, about 0.01M to about 0.45M, about 0.01M to about 0.4M, about 0.01M to about 0.35M, about 0.01M to about 0.3M, about 0.01M to about 0.25M, about 0.01M to about 0.2M, about 0.01M to about 0.1M, about 0.1M to about 0.6M, about 0.1M to about 0.55M, about 0.1M to about 0.5M, about 0.1M to about 0.45M, about 0.1M to about 0.4M, about 0.1M to about 0.35M, about 0.1M to about 0.3M, about 0.2M to about 0.6M, about 0.2M to about 0.55M, about 0.2M to about 0.5M, about 0.2M to about 0.45M, about 0.2M to about 0.4M, about 0.2M to about 0.35M, about 0.2M to about 0.3M, about 0.3M to about 0.6M, about 0.3M to about 0.55M, about 0.3M to about 0.5M, about 0.35M to about 0.6M, about 0.35M to about 0.55M, about 0.35M to about 0.5M, about 0.4M to about 0.6M, about 0.4M to about 0.55M, or about 0.4M to about 0.5M. In certain embodiments, Li in the cathode slurry⁺At a concentration of at least about 0.0001M, at least about 0.0005M, at least about 0.001M, at least about 0.005M, at least about 0.01M, at least about 0.05M, at least about 0.1M, at least about 0.2M, at least about 0.3M, at least about 0.35M, at least about 0.4M, at least about 0.45M, at least about 0.5M, at least about 0.55M, at least about 0.6M, at least about 0.65M, at least about 0.7M, at least about 0.75M, at least about 0.8M, at least about 0.85M, or at least about 0.9M. In certain embodiments, the cathodeLi in the slurry⁺Less than about 1M, less than about 0.95M, less than about 0.9M, less than about 0.85M, less than about 0.8M, less than about 0.75M, less than about 0.7M, less than about 0.65M, less than about 0.6M, less than about 0.55M, less than about 0.5M, less than about 0.45M, less than about 0.4M, less than about 0.35M, less than about 0.3M, less than about 0.25M, less than about 0.2M, less than about 0.15M, less than about 0.1M, less than about 0.05M, less than about 0.01M, less than about 0.005M, or less than about 0.001M.

In certain embodiments, the pH of the cathode slurry is from about 10 to about 14, from about 10 to about 13, from about 10 to about 12, from about 10 to about 11.8, from about 10 to about 11.5, from about 10.3 to about 11.8, from about 11 to about 14, from about 11 to about 13, or from about 12 to about 14. In some embodiments, the pH of the cathode slurry is less than about 13, less than about 12.5, less than about 12, less than about 11.5, less than about 11, less than about 10.5, less than about 10, or less than about 9. In certain embodiments, the pH of the cathode slurry is above about 10, above about 10.5, above about 11, above about 11.5, above about 12, above about 12.5, or above about 13.

The slurry should maintain a stable pH during homogenization because an unstable pH would greatly shorten the useful life of the cell. Typically, when a lithium compound is present in the slurry, the pH of the slurry is found to change only slightly during homogenization. In certain embodiments, the amount of pH change observed during homogenization is from about 0.01 to about 0.5, from about 0.01 to about 0.45, from about 0.01 to about 0.4, from about 0.01 to about 0.35, from about 0.01 to about 0.3, from about 0.01 to about 0.25, from about 0.01 to about 0.2, from about 0.01 to about 0.15, or from about 0.01 to about 0.1. In certain embodiments, the amount of pH reduction observed during homogenization is less than 0.5, less than 0.45, less than 0.4, less than 0.35, less than 0.3, less than 0.2, or less than 0.1.

The thickness of the current collector affects the volume it occupies in the battery, the amount of electrode active material required, and therefore the capacity of the battery. In some embodiments, the current collector has a thickness of about 5 μm to about 30 μm. In certain embodiments, the current collector has a thickness of about 5 μm to about 20 μm, about 5 μm to about 15 μm, about 10 μm to about 30 μm, about 10 μm to about 25 μm, or about 10 μm to about 20 μm.

In certain embodiments, the coating process is performed using a knife coater, a die coater, a transfer coater, a spray coater, a roll coater, a bump coater, a dip coater, or a curtain coater.

Evaporation of the solvent is required to produce a dry porous electrode to produce a battery. After the homogenized slurry is applied on the current collector, the coating film on the current collector may be dried by a dryer to obtain a battery electrode. Any dryer that can dry the coating film on the current collector may be used herein. Some non-limiting examples of dryers include batch dryers, tunnel dryers, and microwave dryers. Some non-limiting examples of tunnel dryers include tunnel hot air dryers, tunnel resistance dryers, tunnel induction dryers, and tunnel microwave dryers.

In some embodiments, a tunnel drying oven for drying a coating film on a current collector comprises one or more heating stages, wherein each heating stage is individually temperature controlled, and wherein each heating stage may comprise independently controlled heating zones.

In certain embodiments, the tunnel oven comprises a first heating section on one side of the conveyor belt and a second heating section on an opposite side of the conveyor belt from the first heating section, wherein each of the first heating section and the second heating section independently comprises one or more heating assemblies and a temperature control system connected to the heating assemblies of the first heating section and the heating assemblies of the second heating section in a manner that monitors and selectively controls the temperature of each heating section.

In some embodiments, the tunnel kiln includes a plurality of heating sections, wherein each heating section includes a separate heating assembly that is operated to maintain a constant temperature within the heating section.

In certain embodiments, each of the first heating section and the second heating section independently has an inlet heating zone and an outlet heating zone, wherein the inlet heating zone and the outlet heating zone each independently comprise one or more heating assemblies and a temperature control system connected to the heating assembly of the inlet heating zone and the heating assembly of the outlet heating zone in a manner that monitors and selectively controls the temperature of each heating zone separately from the temperature control of the other heating zones.

The coating film on the current collector should be dried at a temperature of about 75 c or less in about 20 minutes or less. Drying the coated positive electrode at temperatures above 75 c may result in undesirable decomposition of the cathode, thereby affecting the performance of the positive electrode.

In some embodiments, the coating film on the current collector may be dried at a temperature of about 25 ℃ to about 75 ℃. In certain embodiments, the coating film is dried at a temperature of about 25 ℃ to about 70 ℃, about 25 ℃ to about 65 ℃, about 25 ℃ to about 60 ℃, about 25 ℃ to about 55 ℃, about 25 ℃ to about 50 ℃, about 25 ℃ to about 45 ℃, about 25 ℃ to about 40 ℃, about 30 ℃ to about 75 ℃, about 30 ℃ to about 70 ℃, about 30 ℃ to about 65 ℃, about 30 ℃ to about 60 ℃, about 30 ℃ to about 55 ℃, about 30 ℃ to about 50 ℃, about 35 ℃ to about 75 ℃, about 35 ℃ to about 70 ℃, about 35 ℃ to about 65 ℃, about 35 ℃ to about 60 ℃, about 40 ℃ to about 75 ℃, about 40 ℃ to about 70 ℃, about 40 ℃ to about 65 ℃, or about 40 ℃ to about 60 ℃. In some embodiments, the coating film on the current collector may be dried at a temperature of less than 75 ℃, less than 70 ℃, less than 65 ℃, less than 60 ℃, less than 55 ℃, or less than 50 ℃. In some embodiments, the coating film on the current collector may be dried at a temperature above about 70 ℃, above about 65 ℃, above about 60 ℃, above about 55 ℃, above about 50 ℃, above about 45 ℃, above about 40 ℃, above about 35 ℃, above about 30 ℃ or above about 25 ℃.

In certain embodiments, the conveyor belt is positioned at a rate of from about 1 meter/minute to about 120 meters/minute, from about 1 meter/minute to about 100 meters/minute, from about 1 meter/minute to about 80 meters/minute, from about 1 meter/minute to about 60 meters/minute, from about 1 meter/minute to about 40 meters/minute, from about 10 meters/minute to about 120 meters/minute, from about 10 meters/minute to about 80 meters/minute, from about 10 meters/minute to about 60 meters/minute, from about 10 meters/minute to about 40 meters/minute, from about 25 meters/minute to about 120 meters/minute, from about 25 meters/minute to about 100 meters/minute, from about 25 meters/minute to about 80 meters/minute, from about 25 meters/minute to about 60 meters/minute, from about 50 meters/minute to about 120 meters/minute, a, A speed of about 50 meters/minute to about 100 meters/minute, about 50 meters/minute to about 80 meters/minute, about 75 meters/minute to about 120 meters/minute, about 75 meters/minute to about 100 meters/minute, about 2 meters/minute to about 25 meters/minute, about 2 meters/minute to about 20 meters/minute, about 2 meters/minute to about 16 meters/minute, about 3 meters/minute to about 30 meters/minute, about 3 meters/minute to about 20 meters/minute, or about 3 meters/minute to about 16 meters/minute.

The drying time of the coating film can be adjusted by controlling the length and speed of the conveyor belt. In some embodiments, the coating film on the current collector may be dried for a period of about 1 minute to about 30 minutes, about 1 minute to about 25 minutes, about 2 minutes to about 20 minutes, about 2 minutes to about 17 minutes, about 2 minutes to about 15 minutes, about 2 minutes to about 14 minutes, about 2 minutes to about 10 minutes, about 2 minutes to about 11 minutes, about 2 minutes to about 8 minutes, about 5 minutes to about 30 minutes, about 5 minutes to about 20 minutes, about 5 minutes to about 11 minutes, about 5 minutes to about 14 minutes, about 5 minutes to about 17 minutes, about 5 minutes to about 10 minutes, about 10 minutes to about 30 minutes, or about 10 minutes to about 20 minutes. In certain embodiments, the coating film on the current collector may be dried for a period of less than 5 minutes, less than 8 minutes, less than 10 minutes, less than 11 minutes, less than 14 minutes, less than 17 minutes, or less than 20 minutes. In some embodiments, the coating film on the current collector may be dried for a period of about 5 minutes, about 8 minutes, about 10 minutes, about 11 minutes, about 14 minutes, about 17 minutes, or about 20 minutes.

Since the cathode active material has sufficient activity to chemically react with water, it is necessary to control the overall processing time of the process, particularly steps 1) -5). In some embodiments, the total treatment time of steps 1) -5) is about 2 hours to about 8 hours, about 2 hours to about 7 hours, about 2 hours to about 6 hours, about 2 hours to about 5 hours, about 2 hours to about 4 hours, or about 2 hours to about 3 hours. In certain embodiments, the total treatment time of steps 1) -5) is less than 8 hours, less than 7 hours, less than 6 hours, less than 5 hours, less than 4 hours, or less than 3 hours. In some embodiments, the total treatment time for steps 1) -5) is about 8 hours, about 7 hours, about 6 hours, about 5 hours, about 4 hours, about 3 hours, or about 2 hours.

In some embodiments, the total treatment time of steps 1) -4) or steps 3) -5) is about 2 hours to about 8 hours, about 2 hours to about 7 hours, about 2 hours to about 6 hours, about 2 hours to about 5 hours, about 2 hours to about 4 hours, or about 2 hours to about 3 hours. In certain embodiments, the total treatment time of steps 1) -4) is less than 8 hours, less than 7 hours, less than 6 hours, less than 5 hours, less than 4 hours, less than 3 hours, or less than 2 hours.

In some embodiments, the total treatment time of steps 4) -5) is from about 5 minutes to about 2 hours, from about 5 minutes to about 1.5 hours, from about 5 minutes to about 1 hour, from about 5 minutes to about 30 minutes, from about 10 minutes to about 2 hours, from about 10 minutes to about 1.5 hours, from about 10 minutes to about 1 hour, from about 10 minutes to about 30 minutes, from about 15 minutes to about 2 hours, from about 15 minutes to about 1.5 hours, from about 15 minutes to about 1 hour, or from about 15 minutes to about 30 minutes. In certain embodiments, the total treatment time of steps 4) -5) is less than 2 hours, less than 1.5 hours, less than 1 hour, less than 45 minutes, less than 30 minutes, less than 25 minutes, less than 20 minutes, less than 10 minutes, or less than 5 minutes.

After the coating film on the current collector is dried, a cathode is formed. In some embodiments, the cathode is mechanically compressed to increase the density of the cathode.

An advantage of the method disclosed herein is the use of aqueous solvents in the manufacturing process, saving process time and facilities by avoiding the need to handle or recycle hazardous organic solvents, while improving safety. In addition, by simplifying the overall process, the cost is reduced. Therefore, the method is particularly suitable for industrial processes due to its low cost and easy handling.

As described above, the slurry preparation method disclosed herein has a controlled pH of the cathode slurry, which is advantageous for improving the stability of the slurry, by the manner of adding the cathode active material to the lithium compound disclosed herein. The development of aqueous cathode slurries without degrading battery performance (such as cyclability and capacity) is achieved by the present invention. Batteries comprising a positive electrode prepared according to the present invention exhibit high cycle stability. In addition, the low drying temperature and reduced drying time of the coating film significantly improve the performance of the battery.

Fig. 4 shows the discharge curves of three cells, respectively including a cathode prepared using an NMP-containing slurry, a cathode prepared containing an untreated aqueous slurry and a cathode prepared using an LiOH-treated aqueous slurry according to the present invention. As shown, the LiOH treated aqueous slurry of the present invention produced a battery exhibiting better discharge performance than the conventional untreated aqueous slurry. The results provide further evidence that the LiOH treated slurry preparation method of the present invention significantly improves the electrochemical performance of the cell. In addition, the disclosed process is significantly superior to conventional aqueous processes.

As shown in fig. 4, the battery prepared from the LiOH-treated aqueous slurry of the present invention exhibited similar discharge performance as compared to the battery using the NMP-containing slurry. However, by using an aqueous solvent and a water-soluble material, the method of the present invention reduces the environmental impact of the manufacturing process and reduces production costs, since water-soluble materials are generally cheaper and require less specialized equipment to process. Thus, the present invention can produce lithium ion batteries in a more economical and environmentally friendly manner without sacrificing battery performance.

Analysis of the cathode slurry and its components has revealed useful physical and chemical properties resulting from the present method. Fig. 5 and 6 show infrared spectral data of Polyacrylamide (PAM) exposed to lithium hydroxide and lithium iodide, respectively. The solid line shows the transmission spectrum of untreated PAM mixed with NMC811 and water for only 3 hours. The dashed line shows the transmission spectrum of PAM mixed with lithium salt for 30 minutes and further mixed with NMC811 for 3 hours. It can be seen that the intensity of many peaks has changed after exposure to lithium salts compared to the spectrum of untreated PAM. This indicates that the PAM undergoes a significant chemical change after contact with the lithium salt, as in step b) of the process.

Table 3 below shows ICP mass spectrometry data for NMC811 diluted solutions with various concentrations of LiOH added. The data indicate that less lithium from the cathode active material is dissolved in the solution, thus indicating that the lithium salt inhibits the loss of lithium from the cathode active material. It can be seen that the concentration of the lithium salt added is proportional to the inhibition of lithium loss of the cathode active material.

In some embodiments, lithium loss in the cathode active material is inhibited by 1% to 50% compared to lithium loss of the cathode material in pure water. In certain embodiments, lithium loss in the cathode active material is inhibited by 1% to 20% compared to lithium loss of the cathode material in pure water. In certain embodiments, lithium loss in the cathode active material is inhibited by 1% to 30%, 1.5% to 20%, 2% to 20%, 2.5% to 20%, 3% to 20%, 4% to 20%, 5% to 20%, 10% to 20%, 1.5% to 18%, 2% to 18%, 2.5% to 18%, 3% to 18%, 4% to 18%, 5% to 18%, 8% to 18%, 1.5% to 15%, 2% to 15%, 2.5% to 15%, 3% to 15%, 4% to 15%, 5% to 15%, 10% to 15%, 1.5% to 14%, 2% to 14%, 2.5% to 14%, 3% to 14%, 4% to 14%, 5% to 14%, 1% to 13%, 1.5% to 13%, 2% to 13%, 2.5% to 13%, 3% to 13%, 4% to 13%, 1% to 12%, 12% to 13%, or more than lithium loss in the cathode active material in pure water, 1.5% to 12%, 2% to 12%, 2.5% to 12%, 3% to 12%, 4% to 12%, or 5% to 12%. In some embodiments, lithium loss in the cathode active material is inhibited by 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, 3.5% or more, 4% or more, 4.5% or more, 5% or more, 5.5% or more, 6% or more, 6.5% or more, 7% or more, 7.5% or more, 8% or more, 8.5% or more, 9% or more, 9.5% or more, 10% or more, 10.5% or more, 11% or more, 11.5% or more, 12% or more, 12.5% or more, 13% or more, 13.5% or more, 14% or more, 14.5% or more, 15% or more, as compared to lithium loss in the cathode active material in pure water. In some embodiments, lithium loss in the cathode active material is inhibited by 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14.5% or less, 14% or less, 13.5% or less, 13% or less, 12.5% or less, 12% or less, 11.5% or less, 11% or less, 10.5% or less, 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 2.5% or less, 2% or less, 1.5% or less, as compared to lithium loss in the cathode active material in pure water.

Also provided herein is an electrode assembly including the cathode prepared by the above method. The electrode assembly includes at least one cathode, at least one anode, and at least one separator disposed between the cathode and the anode.

In some embodiments, the electrode assembly is dried after assembly to reduce its moisture content. In other embodiments, at least one component of the electrode assembly is dried prior to assembly of the electrode assembly. In some embodiments, at least one of the components is pre-dried prior to assembly of the electrode assembly. In some embodiments, the separator is pre-dried prior to being assembled to the electrode assembly.

It is not necessary to dry the membrane to a very low moisture content. The residual moisture content of the pre-dried membrane can be further reduced by a subsequent drying step. In some embodiments, the pre-dried membrane has a water content by weight of about 50ppm to about 800ppm, about 50ppm to about 700ppm, about 50ppm to about 600ppm, about 50ppm to about 500ppm, about 50ppm to 400ppm, about 50ppm to about 300ppm, about 50ppm to 200ppm, about 50ppm to 100ppm, about 100ppm to about 500ppm, about 100ppm to about 400ppm, about 100ppm to about 300ppm, about 100ppm to about 200ppm, about 200ppm to about 500ppm, about 200ppm to about 400ppm, about 300ppm to about 800ppm, about 300ppm to about 600ppm, about 300ppm to about 500ppm, about 300ppm to about 400ppm, about 400ppm to about 800ppm, or about 400ppm to about 500ppm, based on the total weight of the pre-dried membrane. In some embodiments, the moisture content in the pre-dried membrane is less than 500ppm, less than 400ppm, less than 300ppm, less than 200ppm, less than 100ppm, or less than 50ppm by weight based on the total weight of the pre-dried membrane.

In certain embodiments, the dried electrode assembly has a water content of about 20ppm to 350ppm, about 20ppm to 300ppm, about 20ppm to 250ppm, about 20ppm to 200ppm, about 20ppm to about 100ppm, about 20ppm to about 50ppm, about 50ppm to about 350ppm, about 50ppm to about 250ppm, about 50ppm to about 150ppm, about 100ppm to about 350ppm, about 100ppm to about 300ppm, about 100ppm to about 250ppm, about 100ppm to about 200ppm, about 100ppm to about 150ppm, about 150ppm to about 350ppm, about 150ppm to about 300ppm, about 150ppm to about 250ppm, about 150ppm to about 200ppm, about 200ppm to about 350ppm, about 250ppm to about 350ppm, or about 300ppm to about 350ppm by weight based on the total weight of the dried electrode assembly.

The following examples are given for the purpose of illustrating embodiments of the invention and are not intended to limit the invention to the particular examples set forth. Unless indicated to the contrary, all parts and percentages are by weight. All numerical values are approximate. When numerical ranges are given, it should be understood that embodiments outside the stated ranges still fall within the scope of the invention. Specific details described in the various embodiments should not be construed as essential features of the invention.

Examples

The pH of the slurry was measured by an electrode type pH meter (ION 2700, Eutech Instruments). The viscosity of the slurry was measured using a rotational viscometer (NDJ-5S, Shanghai JT Electronic Technology Co. Ltd., China).

The peel strength of the dried electrode layer was measured by a peel tester (DZ-106A, from Dongguan Zonhow Test Equipment co.ltd., china). This test measures the average force in newtons required to peel the electrode layer from the current collector at a 180 ° angle per 18mm wide sample. A strip of 18mm wide tape (3M; usa; model 810) was adhered to the surface of the cathode electrode layer. The cathode strip was clamped on the tester and the tape was then folded back at 180 deg. and then placed in a movable jaw and pulled at room temperature at a peel speed of 200 mm/min. The maximum peel force measured was the peel strength. The measurements were repeated 3 times to take an average.

The water content in the electrode assembly was measured by Karl-Fisher titration. The electrode assembly was cut into 1cm x 1cm pieces in a glove box filled with argon. The cut electrode assemblies having a size of 1cm x 1cm were weighed in the sample bottles. The weighed electrode assembly was then placed into a titration vessel for Karl-Fisher titration using a Karl Fisher coulometry moisture meter (831KF coulometer, Metrohm, switzerland). The measurement was repeated 3 times to obtain an average value.

The water content in the membrane was measured by Karl-Fisher titration. The electrode assembly was cut into 1cm x 1cm pieces in a glove box filled with argon. The electrode assembly is divided into an anode layer, a cathode layer and a separator layer. The water content of the separated membrane layers was analyzed by the Karl-Fisher titration method described above. The measurement was repeated 3 times to obtain an average value.

Example 1

A) Preparation of the Positive electrode

A first suspension was prepared by dispersing 0.9g of a conductive agent (SuperP; from Timcal Ltd, Bodio, Switzerland) and 6g of Polyacrylamide (PAM) (15% solids content) in 7.4g of deionized water while stirring with an overhead stirrer (R20, IKA). After the addition, the first suspension was further stirred at 1,200rpm for about 30 minutes at 25 ℃.

An aqueous lithium solution having a LiOH concentration of 0.01M was prepared by dissolving 0.02g of LiOH in 100g of deionized water at 25 ℃. After the addition, the aqueous solution was further stirred at 25 ℃ for about 5 minutes. Then, 7.5g of an aqueous solution was added to the first suspension to prepare a second suspension. After addition, the second suspension was further stirred at 25 ℃ for about 30 minutes.

Thereafter, a third suspension was prepared by adding 28.2g of NMC532 (from new energy co., ltd, tianjiao, shandong, china) to the second suspension while stirring with an overhead stirrer at 25 ℃. The third suspension was then degassed at a pressure of about 10kPa for 1 hour. The third suspension was then further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃ to form a homogenized slurry.

The homogenized slurry was coated on one side of an aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The coated slurry film on the aluminum foil was dried by an electrically heated tunnel drying oven (TH-1A, from south kyoto hao drying equipment ltd, china) at 50 ℃ at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

B) Preparation of the negative electrode

90 wt.% of hard carbon (BTR New Energy Materials Inc., Shenzhen, Guangdong, China), 1.5 wt.% of carboxymethyl cellulose (CMC, BSH-12, DKS Co. Ltd., Japan) as a binder, and 3.5 wt.% of SBR (AL-2001, NIPPON A) were mixed in deionized water&L inc., japan) and 5 wt.% carbon black as a conductive agent. The solid content of the anode slurry was 50 wt.%. The slurry was coated on one side of a copper foil having a thickness of 8 μm using a knife coater having a gap width of about 55 μm. The coating film on the copper foil was dried by a hot air dryer at about 50 ℃ for 2.4 minutes to obtain a negative electrode. The electrodes were then pressed to reduce the coating thickness to 30 μm with an areal density of 10mg/cm²。

C) Button cell assembly

A CR2032 button-type Li battery was assembled in an argon-filled glove box. The coated cathode and anode sheets were cut into disc-shaped cathodes and anodes, and an electrode assembly was assembled by alternately stacking cathode and anode electrode sheets and then housing in a CR2032 type case made of stainless steel. The cathode and anode sheets are held apart by a separator. The separator is a ceramic-coated microporous membrane made of a non-woven fabric (MPM, japan) and has a thickness of about 25 μm. The electrode assembly was then dried in a box-type resistance furnace (DZF-6020, from Shenzhenjac Crystal technologies, Inc., China) under vacuum at 105 ℃ for about 16 hours. The moisture contents of the dried separator and electrode assembly were 200ppm and 300ppm, respectively.

The electrolyte is injected into a case containing the packaged electrode under a high-purity argon atmosphere having a humidity and an oxygen content of less than 3ppm, respectively. The electrolyte is ethylene carbonate (E) with the volume ratio of 1:1:1C) Mixtures of Ethyl Methyl Carbonate (EMC) and dimethyl carbonate (DMC) containing LiPF₆(1M) of a solution. After electrolyte injection, the button cells were vacuum sealed and then mechanically pressed using a press tool with a standard circular shape.

D) Electrochemical measurements

Button cells were analyzed in a constant current mode using a multichannel cell tester (BTS-4008-5V10mA, from Neware Electronics Co. Ltd., China). After 1 cycle at C/20, charge and discharge were performed at a C/2 rate. At 25 ℃, the discharge capacity was obtained by conducting charge/discharge cycle test of the battery at a current density of C/2 between 3.0V and 4.3V. The electrochemical performance of the coin cells of example 1 was measured and is shown in table 1 below.

Example 2

A positive electrode was prepared in the same manner as in example 1, except that 0.12g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.05M was prepared, and a second suspension was prepared by adding 7.5g of the aqueous solution to the first suspension.

Example 3

A positive electrode was prepared in the same manner as in example 1, except that 1.20g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.5M was prepared, and a second suspension was prepared by adding 7.5g of the aqueous solution to the first suspension.

Example 4

A positive electrode was prepared in the same manner as in example 2, except that the second suspension was further stirred at 25 ℃ for about 5 minutes.

Example 5

A positive electrode was prepared in the same manner as in example 2, except that the second suspension was further stirred at 25 ℃ for about 60 minutes.

Example 6

A positive electrode was prepared in the same manner as in example 2, except that 0.67g of LiI was dissolved with 100g of deionized water to prepare an aqueous solution having a LiI concentration of 0.05M at 25 ℃.

Example 7

A positive electrode was prepared in the same manner as in example 2, except that 0.33g of LiAc was dissolved in 100g of deionized water to prepare an aqueous solution having a LiAc concentration of 0.05M at 25 ℃.

Comparative example 1

28.2g NMC532 (from New energy Co., Ltd., Tianjiao, Shandong, China), 0.9g conductive agent (SuperP; from Timcal Ltd, Bodio, Switzerland) and 6g polyacrylamide binder (15% solids content) were dispersed in 14.9g deionized water while stirring with an overhead stirrer to prepare a positive electrode slurry. The slurry was degassed at a pressure of about 10kPa for 1 hour. Then, the slurry was further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃.

The homogenized slurry was coated on one side of an aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The coated slurry film on the aluminum foil was dried at 50 c by an electrically heated tunnel oven (TH-1A, from south kyoto hao drying equipment ltd, china) at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

Comparative example 2

28.2g NMC532 (from New energy Co., Ltd., Shandong Tianjiao, China), 0.9g conductive agent (SuperP; from Timcal Ltd., Bodio, Switzerland) and 9g polyvinylidene fluoride (PVDF; a 10 wt% solution of NMP) were dispersed in 11.9g N-methyl-2-pyrrolidone (NMP;. gtoreq.99%, Sigma-Aldrich, USA);5130 from Solvay s.a., belgium), while stirring with an overhead stirrer. The slurry was degassed at a pressure of about 10kPa for 1 hour. Then, the slurry was further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃.

The homogenized slurry was coated on one side of an aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The coated slurry film on the aluminum foil was dried at 50 c by an electrically heated tunnel oven (TH-1A, from south kyoto hao drying equipment ltd, china) at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

Preparation of negative electrodes of examples 2 to 7 and comparative examples 1 to 2

Negative electrodes of examples 2 to 7 and comparative examples 1 to 2 were prepared by the method of example 1.

Assembly of button cells of examples 2 to 7 and comparative examples 1 to 2

The button cells of examples 2 to 7 and comparative examples 1 to 2 were assembled by the method of example 1.Examples 2 to 7 and comparison Electrochemical measurements of examples 1-2

The electrochemical performance of the button cells of examples 2 to 7 and comparative examples 1 to 2 was measured by the method of example 1, and the test results are shown in table 1 below.

Example 8

A positive electrode was prepared in the same manner as in example 1, except that 28.2g of NMC532 was replaced with the same weight of NMC622 (from shandong tianjiao co., china).

Example 9

A positive electrode was prepared in the same manner as in example 8, except that 0.12g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.05M was prepared, and a second suspension was prepared by adding 7.5g of the aqueous solution to the first suspension.

Example 10

A positive electrode was prepared in the same manner as in example 8, except that 1.20g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.5M was prepared, and a second suspension was prepared by adding 7.5g of the aqueous solution to the first suspension.

Practice ofExample 11

A positive electrode was prepared in the same manner as in example 9, except that the second suspension was further stirred at 25 ℃ for about 5 minutes.

Example 12

A positive electrode was prepared in the same manner as in example 9, except that the second suspension was further stirred at 25 ℃ for about 60 minutes.

Example 13

A positive electrode was prepared in the same manner as in example 9, except that 0.67g of LiI was dissolved with 100g of deionized water to prepare an aqueous solution having a LiI concentration of 0.05M at 25 ℃.

Example 14

A positive electrode was prepared in the same manner as in example 9, except that 0.33g of LiAc was dissolved in 100g of deionized water to prepare an aqueous solution having a LiAc concentration of 0.05M at 25 ℃.

Comparative example 3

A positive electrode was prepared in the same manner as in comparative example 1, except that 28.2g of NMC533 was replaced with the same weight of NMC 622.

Comparative example 4

A positive electrode was prepared in the same manner as in comparative example 2, except that 28.2g of NMC533 was replaced with the same weight of NMC 622.

Preparation of negative electrodes of examples 8 to 14 and comparative examples 3 to 4

Negative electrodes of examples 8 to 14 and comparative examples 3 to 4 were prepared by the method of example 1.

Assembly of button cells of examples 8 to 14 and comparative examples 3 to 4

The button cells of examples 8 to 14 and comparative examples 3 to 4 were assembled by the method of example 1.Examples 8 to 14 and ratios Electrochemical measurements of comparative examples 3 to 4

The electrochemical performance of the button cells of examples 8 to 14 and comparative examples 3 to 4 was measured by the method of example 1, and the test results are shown in table 1 below.

Example 15

A) Preparation of the Positive electrode

A first suspension was prepared by dispersing 0.9g of conductive agent (SuperP; from Timcal Ltd, Bodio, Switzerland) and 6g of PAM binder in 4.9g of deionized water while stirring with an overhead stirrer (R20, IKA). After the addition, the second suspension was further stirred at 1,200rpm for about 30 minutes at 25 ℃.

An aqueous lithium solution having a LiOH concentration of 0.01M was prepared by dissolving 0.02g of LiOH in 100g of deionized water at 25 ℃. After the addition, the aqueous solution was further stirred at 25 ℃ for about 5 minutes. Then, 10g of an aqueous solution was added to the first suspension to prepare a second suspension. After addition, the second suspension was further stirred at 25 ℃ for about 30 minutes.

Thereafter, 28.2g of NMC811 (from new energy co., ltd. Tianjiao, Shandong, China) was added to the second suspension while stirring with an overhead stirrer at 25 ℃ to prepare a third suspension. The third suspension was then degassed at a pressure of about 10kPa for 1 hour. The third suspension was then further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃ to form a homogenized slurry.

The homogenized slurry was coated onto the side of the carbon coated aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The thickness of the carbon coating was 1 μm. The coated slurry film on the aluminum foil was dried by an electrically heated tunnel drying oven (TH-1A, from south kyoto hao drying equipment ltd, china) at 50 ℃ at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

Example 16

A positive electrode was prepared in the same manner as in example 15, except that 0.12g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.05M was prepared, and a second suspension was prepared by adding 10g of the aqueous solution to the first suspension.

Example 17

A positive electrode was prepared in the same manner as in example 15, except that 1.20g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.5M was prepared, and a second suspension was prepared by adding 10g of the aqueous solution to the first suspension.

Example 18

A positive electrode was prepared in the same manner as in example 16, except that the second suspension was further stirred at 25 ℃ for about 5 minutes.

Example 19

A positive electrode was prepared in the same manner as in example 16, except that the second suspension was further stirred at 25 ℃ for about 60 minutes.

Example 20

A positive electrode was prepared in the same manner as in example 16, except that 0.67g of LiI was dissolved with 100g of deionized water to prepare an aqueous solution having a LiI concentration of 0.05M at 25 ℃.

Example 21

A positive electrode was prepared in the same manner as in example 16, except that 0.33g of LiAc was dissolved in 100g of deionized water to prepare an aqueous solution having a LiAc concentration of 0.05M at 25 ℃.

Example 22

A positive electrode was prepared in the same manner as in example 16, except that 0.34g of LiNO was dissolved in 100g of deionized water₃Preparation of LiNO at 25 deg.C₃Aqueous solution with concentration of 0.05M.

Comparative example 5

28.2g of NMC811 (from New energy Co., Ltd., Tianjiao, Shandong, China), 0.9g of a conductive agent (SuperP; from Timcal Ltd, Bodio, Switzerland) and 10g of PAM binder (15% solids content) were dispersed in 14.9g of deionized water while stirring with an overhead stirrer to prepare a positive electrode slurry. The slurry was degassed at a pressure of about 10kPa for 1 hour. Then, the slurry was further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃.

The homogenized slurry was coated onto the side of the carbon coated aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The thickness of the carbon coating was 1 μm. The coated slurry film on the aluminum foil was dried at 50 c by an electrically heated tunnel oven (TH-1A, from south kyoto hao drying equipment ltd, china) at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

Comparative example 6

28.2g NMC811 (from New energy Co., Tianjiao, Shandong, China), 0.9g conductive agent (SuperP; from Timcal Ltd, Bodio, Switzerland) and 9g PVDF (9 g) were dispersed in 11.9g NMP (. gtoreq.99%, Sigma-Aldrich, USA)5130 from Solvay s.a., belgium), while stirring with an overhead stirrer. The slurry was degassed at a pressure of about 10kPa for 1 hour. Then, the slurry was further stirred at a speed of 1,200rpm for about 60 minutes at 25 ℃.

The homogenized slurry was coated onto the side of the carbon coated aluminum foil having a thickness of 14 μm as a current collector using a knife coater having a gap width of 60 μm. The thickness of the carbon coating was 1 μm. The coated slurry film on the aluminum foil was dried at 50 c by an electrically heated tunnel oven (TH-1A, from south kyoto hao drying equipment ltd, china) at a conveyor speed of about 5 m/min to form a cathode electrode layer. The drying time was about 6 minutes. The electrodes were then pressed to reduce the thickness of the cathode electrode layer to 35 μm.

Preparation of negative electrodes of examples 15 to 22 and comparative examples 5 to 6

Negative electrodes of examples 15 to 22 and comparative examples 5 to 6 were prepared by the method of example 1.Examples 15 to 22 and comparison Assembly of button cells of examples 5 to 6

Assembly implementation by the method of example 1The coin cells of examples 15 to 22 and comparative examples 5 to 6.Examples 15 to 22 and electrochemical measurements of comparative examples 5 to 6

The electrochemical properties of the button cells of examples 15 to 22 and comparative examples 5 to 6 were measured by the method of example 1, and the test results are shown in table 2 below.

Example 23

A positive electrode was prepared in the same manner as in example 15, except that 28.2g of NMC811 was replaced with the same weight of NCA.

Example 24

A positive electrode was prepared in the same manner as in example 23, except that 0.12g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.05M was prepared, and a second suspension was prepared by adding 10g of the aqueous solution to the first suspension.

Example 25

A positive electrode was prepared in the same manner as in example 23, except that 1.20g of LiOH was dissolved with 100g of deionized water, an aqueous solution having a LiOH concentration of 0.5M was prepared, and a second suspension was prepared by adding 10g of the aqueous solution to the first suspension.

Example 26

A positive electrode was prepared in the same manner as in example 24, except that the second suspension was further stirred at 25 ℃ for about 5 minutes.

Example 27

A positive electrode was prepared in the same manner as in example 24, except that the second suspension was further stirred at 25 ℃ for about 60 minutes.

Example 28

A positive electrode was prepared in the same manner as in example 24 except that 0.67g of LiI was dissolved in 100g of deionized water to prepare an aqueous solution having a LiI concentration of 0.014M at 25 ℃.

Example 29

A positive electrode was prepared in the same manner as in example 24, except that 0.33g of LiAc was dissolved in 100g of deionized water to prepare an aqueous solution having a LiAc concentration of 0.014M at 25 ℃.

Example 30

A positive electrode was prepared in the same manner as in example 2, except that a copolymer of acrylamide and acrylonitrile was used as a binder (solid content: 15%).

Example 31

A positive electrode was prepared in the same manner as in example 2, except that a copolymer of acrylamide and methacrylic acid was used as a binder (solid content: 15%).

Example 32

A positive electrode was prepared in the same manner as in example 2, except that NMC532 was used as a core and Li was used_0.95Ni_0.53Mn_0.29Co_0.15Al_0.03O₂A core-shell cathode active material (C-S) as a shell. The particle size D50 of the cathode active material was about 35 μm. The thickness of the shell is about 3 μm.

Comparative example 7

A positive electrode was prepared in the same manner as in comparative example 5, except that 28.2g of NMC811 was replaced with NCA of the same weight.

Comparative example 8

A positive electrode was prepared in the same manner as in comparative example 6, except that 28.2g of NMC811 was replaced with NCA of the same weight.

Preparation of negative electrodes of examples 23 to 32 and comparative examples 7 to 8

Negative electrodes of examples 23 to 32 and comparative examples 7 to 8 were prepared by the method of example 1.

Assembly of button cells of examples 23 to 32 and comparative examples 7 to 8

The button cells of examples 23 to 32 and comparative examples 7 to 8 were assembled by the method of example 1.Examples 23 to 32 and electrochemical measurements of comparative examples 7 to 8

The electrochemical properties of the button cells of examples 23 to 32 and comparative examples 7 to 8 were measured by the method of example 1, and the test results are shown in table 2 below.