阅读说明：本技术 一种锂离子电池极片、其制备方法和用途 (Lithium ion battery pole piece, preparation method and application thereof ) 是由 龚小曼 刘成 徐晓东 任建国 于 2020-05-28 设计创作，主要内容包括：本发明公开了一种锂离子电池极片、其制备方法和用途。所述锂离子电池极片包括集流体、粘结膜及电极材料层,所述集流体形成有三维网状多孔,所述粘结膜附着于所述集流体及所述三维网状多孔的孔壁表面,所述电极材料层附着于所述粘结膜的表面。本发明锂离子电池极片以三维网状多孔的集流体替代传统的集流体,具有良好的柔韧性和热力学稳定性,不仅可以用于常规的锂电领域,也能应用于柔性电池领域,其三维多孔网状骨架结构可有效增大与电解液的接触面积,其支撑的活性物质在三维空间上的分布也减小了充放电过程中的离子传输途径,且无需使用粘结剂,可将活性物质充分地黏附于集流体的三维骨架上,有利于活性位点在空间上的分散和导电性的提高。(The invention discloses a lithium ion battery pole piece, a preparation method and application thereof. The lithium ion battery pole piece comprises a current collector, an adhesive film and an electrode material layer, wherein the current collector is formed with three-dimensional reticular pores, the adhesive film is attached to the current collector and the pore wall surface of the three-dimensional reticular pores, and the electrode material layer is attached to the surface of the adhesive film. The lithium ion battery pole piece of the invention replaces the traditional current collector with the three-dimensional reticular porous current collector, has good flexibility and thermodynamic stability, can be used in the field of conventional lithium batteries and flexible batteries, can effectively increase the contact area with electrolyte by the three-dimensional porous reticular skeleton structure, reduces the ion transmission path in the charging and discharging process by the distribution of the supported active substance on the three-dimensional space, does not need to use a binder, can fully adhere the active substance to the three-dimensional skeleton of the current collector, and is beneficial to the dispersion of active sites on the space and the improvement of the conductivity.)

1. The lithium ion battery pole piece is characterized by comprising a current collector, an adhesive film and an electrode material layer, wherein three-dimensional reticular pores are formed on the current collector, the adhesive film is attached to the surface of the current collector and the surface of the pore wall of the three-dimensional reticular pores, and the electrode material layer is attached to the surface of the adhesive film.

2. The lithium ion battery pole piece of claim 1, wherein the electrode material layer comprises a conductive agent and an active material;

preferably, the active material includes a positive electrode active material or a negative electrode active material;

preferably, the negative active material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, a silicon/carbon composite, and a silicon/oxygen/carbon composite;

preferably, the positive electrode active material includes at least one of lithium iron phosphate, doped lithium iron phosphate, lithium cobaltate, doped lithium cobaltate, lithium nickelate, doped lithium nickelate, lithium manganate and doped lithium manganate;

preferably, the conductive agent includes a graphene oxide-based material;

preferably, in the conductive agent, the content of the graphene oxide material is 30 wt% to 70 wt%;

preferably, the conductive agent further includes at least one of carbon black, conductive graphite, carbon fiber, and carbon nanotube;

preferably, the conductive agent is attached to a surface of the adhesive film;

preferably, the adhesive film contains an amino group;

preferably, the acting force between the conductive agent and the bonding film is adhesion and chemical crosslinking;

preferably, the force between the active substance and the adhesive film is an adhesive effect.

3. The lithium ion battery pole piece of claim 1 or 2, wherein the current collector comprises at least one of polyurethane foam, phenolic foam, polystyrene foam, polyethylene foam, and polyvinyl chloride foam;

preferably, the thickness of the lithium ion battery pole piece is 1 mm-3 mm;

preferably, the porosity of the lithium ion battery pole piece is 70% -90%;

preferably, in the lithium ion battery pole piece, the content of the adhesive film is 1 wt% -10 wt%;

preferably, in the lithium ion battery pole piece, the content of the current collector is 5 wt% to 30 wt%;

preferably, in the lithium ion battery pole piece, the content of the active substance is 50 wt% -90 wt%;

preferably, in the lithium ion battery pole piece, the content of the conductive agent is 2 wt% to 8 wt%.

4. A preparation method of a lithium ion battery pole piece is characterized by comprising the following steps:

dipping the current collector in the bonding solution to form a bonding film to obtain a modified current collector;

and dipping the modified current collector into electrode slurry to obtain the lithium ion battery pole piece.

5. The method of claim 4, wherein the bonding solution is prepared by a process comprising: mixing a dopamine hydrochloride solution with a phosphoric acid buffer solution, and adjusting the pH value of the solution to obtain a bonding solution;

preferably, the concentration of the phosphoric acid buffer solution is 0.02 mol/L-0.2 mol/L;

preferably, the pH value of the phosphoric acid buffer solution is 8.0-9.0;

preferably, the concentration of the dopamine hydrochloride solution is 0.1 mg/mL-5 mg/mL;

preferably, the pH value of the adjusted solution is 8.2-8.6;

preferably, after the pH value of the solution is adjusted, a stirring process is also included;

preferably, the stirring time is 0.5-4 h;

preferably, the stirring speed is 500 rpm-1000 rpm;

preferably, the porosity of the current collector is 70% to 90%;

preferably, the thickness of the current collector is 1 mm-3 mm;

preferably, the forming of the adhesive film includes: dipping the current collector in the bonding solution, then taking out, and repeatedly carrying out the dipping and taking out processes for 2-5 times, wherein the time of each dipping is preferably 0.5-2 h;

preferably, after the process of forming the adhesive film, a drying process is further included;

preferably, the drying is vacuum drying, preferably drying for 4-8 h at 60-80 ℃;

preferably, the method further comprises pretreating the current collector;

preferably, the pre-treatment comprises: soaking the current collector in an alkaline solution, and then cleaning with deionized water;

preferably, the alkaline solution comprises NaOH solution, Na₂CO₃Solution and NaHCO₃At least one of a solution;

preferably, the concentration of the alkaline solution is 2 wt% to 10 wt%;

preferably, the soaking time is 20min to 60 min.

6. The production method according to claim 4 or 5, wherein the production method of the electrode paste comprises: mixing a solvent, a dispersant, a conductive agent and an active substance to obtain the electrode slurry;

preferably, the dispersant comprises at least one of sodium alginate, sodium carboxymethylcellulose, PVDF and polyacrylic acid;

preferably, the solvent comprises at least one of water and NMP;

preferably, the mass ratio of the active substance to the conductive agent to the dispersing agent is (85-95): 3-10): 1-5;

preferably, the active material is an anode active material, and the particle size D90 of the anode active material is less than or equal to 30 μm;

preferably, the active material is a positive electrode active material, and the particle size D90 of the positive electrode active material is less than or equal to 20 μm;

preferably, the solvent, the dispersant, the conductive agent and the active substance are mixed in at least one of ultrasonic dispersion and agitation;

preferably, the power of the ultrasonic dispersion is 500W-1000W;

preferably, the time of ultrasonic dispersion is 0.5 h-2 h;

preferably, the electrode slurry is negative electrode slurry, and the viscosity of the negative electrode slurry is 2000 to 6000mPa & s;

preferably, the electrode slurry is positive electrode slurry, and the viscosity of the positive electrode slurry is 4000 to 8000mPa & s;

preferably, the solid content of the cathode electrode slurry is 40 wt% to 50 wt%;

preferably, the solid content of the positive electrode slurry is 50 wt% to 80 wt%.

7. The preparation method according to any one of claims 4 to 6, wherein the modified current collector is immersed in the electrode slurry for 0.5 to 4 hours;

preferably, the modified current collector further comprises the processes of drying, rolling and slicing after being immersed in the electrode slurry;

preferably, the drying temperature is 50-70 ℃;

preferably, the drying time is 4-8 h;

preferably, the rolling pressure is 1MPa to 3 MPa.

8. Preparation process according to one of claims 4 to 7, characterized in that it comprises the following steps:

(1) mixing a dopamine hydrochloride solution with the concentration of 0.1-5 mg/mL and a phosphoric acid buffer solution with the concentration of 0.02-0.2 mol/L, adjusting the pH value of the solution to 8.2-8.6, stirring at the speed of 500-1000 rpm for 0.5-4 h, wherein the pH value of the phosphate buffer solution is 8.0-9.0 to obtain a bonding solution, then soaking a current collector with the porosity of 70-90% and the thickness of 1-3 mm in the bonding solution, then taking out, repeatedly soaking and taking out for 2-5 times, wherein the soaking time is 0.5-2 h each time, and drying at the temperature of 60-80 ℃ for 4-8 h to obtain a modified current collector;

(2) mixing a dispersing agent, a conductive agent and a negative active substance according to the mass ratio of the negative active substance with the particle size D90 of less than or equal to 30 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain negative electrode slurry with the viscosity of 2000-6000 mPa & s and the solid content of 40-50 wt%;

or mixing the dispersing agent, the conductive agent and the positive active substance according to the mass ratio of the positive active substance with the particle size D90 of less than or equal to 20 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain positive electrode slurry with the viscosity of 4000-8000 mPa & s and the solid content of 50-80 wt%;

(3) and dipping the modified current collector in the negative electrode slurry or the positive electrode slurry for 0.5-4 h, then taking out, drying at the temperature of 50-70 ℃ for 4-8 h, and performing rolling and slicing processes under the pressure of 1-3 MPa to obtain the lithium ion battery pole piece.

9. A lithium ion battery, characterized in that the lithium ion battery comprises a lithium ion battery pole piece according to any one of claims 1 to 3.

10. The lithium ion battery of claim 9, wherein the lithium ion battery comprises a positive pole piece and a negative pole piece;

preferably, the positive electrode plate is the lithium ion battery plate of any one of claims 1 to 3;

preferably, the negative electrode plate is the lithium ion battery electrode plate of any one of claims 1 to 3.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery pole piece, and a preparation method and application thereof.

Background

The lithium ion battery has been widely developed and utilized due to its advantages of high working voltage, large energy density, long cycle life, small self-discharge, no memory effect, etc., and has rapidly occupied the market of small portable electronic consumer products, and is also gradually becoming a power source of new energy automobiles. However, with the continuous development of scientific technology, especially the gradual application of flexible/wearable devices, the development of thin, light, flexible and bendable lithium ion batteries is urgently needed.

The conventional lithium ion battery electrode is prepared by uniformly mixing an electrode active material with a conductive agent and a binder and then adhering the mixture to a metal current collector by coating. The adhesive has poor conductivity, is not beneficial to lithium ions entering into electrode active substances and increases the polarization of the electrode; the metal current collector (usually copper foil or aluminum foil) increases the overall mass of the electrode, so that the specific capacity of the electrode is greatly reduced. Meanwhile, irreversible deformation of the metal current collector and the falling of the surface electrode material may be caused during repeated bending, folding and stretching processes, thereby causing the battery to fail. The lithium ion battery prepared based on the electrode can not be used as a flexible energy storage device.

Therefore, there is an urgent need to find some electrode materials which are flexible themselves or to prepare and produce flexible lithium ion batteries using a composite material and a flexible substrate.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a lithium ion battery pole piece, a preparation method and application thereof. The lithium ion battery pole piece has good flexibility, good conductivity and good electrochemical performance, has universality and is beneficial to industrial production.

In order to achieve the purpose, the invention adopts the following technical scheme:

one objective of the present invention is to provide a lithium ion battery electrode plate, which includes a current collector, an adhesive film and an electrode material layer, wherein the current collector is formed with a three-dimensional mesh, the adhesive film is attached to the surface of the current collector and the surface of the pore wall of the three-dimensional mesh, and the electrode material layer is attached to the surface of the adhesive film.

Preferably, the electrode material layer comprises a conductive agent, preferably a conductive agent containing a carboxyl group;

preferably, the electrode material layer includes an active material;

preferably, the active material includes a positive electrode active material or a negative electrode active material;

preferably, the negative active material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, a silicon/carbon composite, and a silicon/oxygen/carbon composite;

preferably, the positive electrode active material includes at least one of lithium iron phosphate, doped lithium iron phosphate, lithium cobaltate, doped lithium cobaltate, lithium nickelate, doped lithium nickelate, lithium manganate and doped lithium manganate;

the doping elements in the doped lithium iron phosphate, the doped lithium cobalt oxide, the doped lithium nickel oxide and the doped lithium manganese oxide are not limited, and can be selected by a person skilled in the art according to actual needs.

Preferably, the conductive agent comprises a graphene oxide material, preferably graphene oxide with a transverse dimension of 5-20 μm;

preferably, in the conductive agent, the content of the graphene oxide material is 30 wt% to 70 wt%;

preferably, the conductive agent further includes at least one of carbon black, conductive graphite, carbon fiber, and carbon nanotube;

preferably, the conductive agent is attached to a surface of the adhesive film;

preferably, the adhesive film contains amino groups, preferably a polydopamine film;

preferably, the acting force between the conductive agent and the bonding film is adhesion and chemical crosslinking;

preferably, the force between the active substance and the adhesive film is an adhesive effect.

Preferably, the current collector comprises at least one of polyurethane foam, phenolic foam, polystyrene foam, polyethylene foam, and polyvinyl chloride foam;

preferably, the thickness of the lithium ion battery pole piece is 1 mm-3 mm;

preferably, the porosity of the lithium ion battery pole piece is 70% -90%;

preferably, in the lithium ion battery pole piece, the content of the adhesive film is 1 wt% -10 wt%;

preferably, in the lithium ion battery pole piece, the content of the current collector is 5 wt% to 30 wt%;

preferably, in the lithium ion battery pole piece, the content of the active substance is 50 wt% -90 wt%;

preferably, in the lithium ion battery pole piece, the content of the conductive agent is 2 wt% to 8 wt%.

The invention also aims to provide a preparation method of a lithium ion battery pole piece, which comprises the following steps:

dipping the current collector in the bonding solution to form a bonding film to obtain a modified current collector;

and dipping the modified current collector into electrode slurry to obtain the lithium ion battery pole piece.

Preferably, the preparation process of the binding solution comprises: mixing a dopamine hydrochloride solution with a phosphoric acid buffer solution, and adjusting the pH value of the solution to obtain a bonding solution;

preferably, the concentration of the phosphoric acid buffer solution is 0.02 mol/L-0.2 mol/L;

preferably, the pH value of the phosphoric acid buffer solution is 8.0-9.0;

preferably, the concentration of the dopamine hydrochloride solution is 0.1 mg/mL-5 mg/mL;

preferably, the pH value of the adjusted solution is 8.2-8.6;

preferably, after the pH value of the solution is adjusted, a stirring process is also included;

preferably, the stirring time is 0.5-4 h;

preferably, the stirring speed is 500 rpm-1000 rpm;

preferably, the porosity of the current collector is 70% to 90%;

preferably, the thickness of the current collector is 1 mm-3 mm;

preferably, the forming of the adhesive film includes: dipping the current collector in the bonding solution, then taking out, and repeatedly carrying out the dipping and taking out processes for 2-5 times, wherein the time of each dipping is preferably 0.5-2 h;

preferably, after the process of forming the adhesive film, a drying process is further included;

preferably, the drying is vacuum drying, preferably drying for 4-8 h at 60-80 ℃;

preferably, the method further comprises pretreating the current collector;

preferably, the pre-treatment comprises: soaking the current collector in an alkaline solution, and then cleaning with deionized water;

preferably, theThe alkaline solution comprises NaOH solution and Na₂CO₃Solution and NaHCO₃At least one of a solution;

preferably, the concentration of the alkaline solution is 2 wt% to 10 wt%;

preferably, the soaking time is 20min to 60 min.

Preferably, the preparation method of the electrode slurry comprises the following steps: mixing a solvent, a dispersant, a conductive agent and an active substance to obtain the electrode slurry;

preferably, the dispersant comprises at least one of sodium alginate, sodium carboxymethylcellulose, PVDF and polyacrylic acid;

preferably, the mass ratio of the active substance to the conductive agent to the dispersing agent is (85-95): 3-10): 1-5;

preferably, the active material is an anode active material, and the particle size D90 of the anode active material is less than or equal to 30 μm;

preferably, the active material is a positive electrode active material, and the particle size D90 of the positive electrode active material is less than or equal to 20 μm;

preferably, the solvent comprises at least one of water and NMP;

preferably, the solvent, the dispersant, the conductive agent and the active substance are mixed in at least one of ultrasonic dispersion and agitation;

preferably, the power of the ultrasonic dispersion is 500W-1000W;

preferably, the time of ultrasonic dispersion is 0.5 h-2 h;

preferably, the electrode slurry is negative electrode slurry, and the viscosity of the negative electrode slurry is 2000 to 6000mPa & s;

preferably, the electrode slurry is positive electrode slurry, and the viscosity of the positive electrode slurry is 4000 to 8000mPa & s;

preferably, the solid content of the cathode electrode slurry is 40 wt% to 50 wt%;

preferably, the solid content of the positive electrode slurry is 50 wt% to 80 wt%.

Preferably, the modified current collector is immersed in the electrode slurry for 0.5-4 h;

preferably, the modified current collector further comprises the processes of drying, rolling and slicing after being immersed in the electrode slurry;

preferably, the drying temperature is 50-70 ℃;

preferably, the drying time is 4-8 h;

preferably, the rolling pressure is 1MPa to 3 MPa.

As a preferred technical scheme, the preparation method of the lithium ion battery pole piece comprises the following steps:

(1) mixing a dopamine hydrochloride solution with the concentration of 0.1-5 mg/mL and a phosphoric acid buffer solution with the concentration of 0.02-0.2 mol/L, adjusting the pH value of the solution to 8.2-8.6, stirring at the speed of 500-1000 rpm for 0.5-4 h, wherein the pH value of the phosphate buffer solution is 8.0-9.0 to obtain a bonding solution, then soaking a current collector with the porosity of 70-90% and the thickness of 1-3 mm in the bonding solution, then taking out, repeatedly soaking and taking out for 2-5 times, wherein the soaking time is 0.5-2 h each time, and drying at the temperature of 60-80 ℃ for 4-8 h to obtain a modified current collector;

(2) mixing a dispersing agent, a conductive agent and a negative active substance according to the mass ratio of the negative active substance with the particle size D90 of less than or equal to 30 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain negative electrode slurry with the viscosity of 2000-6000 mPa & s and the solid content of 40-50 wt%;

or mixing the dispersing agent, the conductive agent and the positive active substance according to the mass ratio of the positive active substance with the particle size D90 of less than or equal to 20 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain positive electrode slurry with the viscosity of 4000-8000 mPa & s and the solid content of 50-80 wt%;

(3) and dipping the modified current collector in the negative electrode slurry or the positive electrode slurry for 0.5-4 h, then taking out, drying at the temperature of 50-70 ℃ for 4-8 h, and performing rolling and slicing processes under the pressure of 1-3 MPa to obtain the lithium ion battery pole piece.

The invention also aims to provide a lithium ion battery, which comprises the lithium ion battery pole piece.

Preferably, the lithium ion battery comprises a positive pole piece and a negative pole piece.

Preferably, the positive electrode plate is one of the lithium ion battery electrode plates.

Preferably, the negative electrode plate is a lithium ion battery electrode plate described in one of the purposes.

Advantages of embodiments of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

In a first aspect, an embodiment of the present invention provides a lithium ion battery electrode plate, where the lithium ion battery electrode plate includes a current collector, an adhesive film, and an electrode material layer, where the current collector is formed with a three-dimensional mesh, the adhesive film is attached to a surface of the current collector and a surface of a hole wall of the three-dimensional mesh, and the electrode material layer is attached to a surface of the adhesive film.

The lithium ion battery pole piece of the invention replaces the traditional current collector (copper foil and aluminum foil) with the three-dimensional mesh porous current collector, the three-dimensional porous mesh skeleton structure of the lithium ion battery pole piece can effectively increase the contact area with the electrolyte, so that the electrolyte is more fully soaked, the distribution of the supported active substances on the three-dimensional space also reduces the ion transmission path in the charging and discharging process, and no binder is needed.

The lithium ion battery pole piece disclosed by the invention has the advantages of good flexibility and thermodynamic stability, good processing performance, simple preparation process, good compatibility with the existing sheet-making process and contribution to industrial production.

In an embodiment of the present invention, the electrode material layer includes an active material.

In the embodiment of the present invention, the electrode material layer includes a conductive agent, and preferably, the conductive agent includes a conductive agent containing a carboxyl group, and the carboxyl group and an amino group on the adhesive film form a cross-linked structure, thereby further enhancing the conductivity of the three-dimensional skeleton.

In the embodiment of the present invention, the conductive agent includes a graphene oxide material or a graphene material containing an oxygen functional group, and a part of the group is removed by subjecting graphene oxide to a reduction reaction such as heat treatment or acid treatment, but the oxygen functional group is also present.

In the embodiment of the invention, the sheet transverse dimension of the graphene oxide material is 5 μm to 20 μm, for example, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm or 18 μm, and the like, and the sheet transverse dimension is too small, so that the wrapping of the current collector skeleton is incomplete, and too large results in the stacking of graphene sheets, and good wrapping cannot be formed. In the conductive agent, the content of the graphene oxide-based material is 30 wt% to 70 wt%, for example, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%. The content of the graphene oxide material is too high, which causes the decrease of conductivity and the increase of irreversible capacity, and the content is too low, the chemical crosslinking effect is weak, and the conductivity is poor.

In an embodiment of the present invention, the conductive agent further includes at least one of carbon black, conductive graphite, carbon fiber, and carbon nanotube.

In the embodiment of the invention, the conductive agent is attached to the surface of the adhesive film.

In an embodiment of the present invention, the current collector includes at least one of polyurethane foam, phenolic foam, polystyrene foam, polyethylene foam, and polyvinyl chloride foam, and preferably, polyurethane foam.

In an embodiment of the present invention, the adhesive film contains an amino group, and is preferably a polydopamine film.

In the embodiment of the invention, the acting force between the conductive agent and the bonding film is adhesion and chemical crosslinking.

In an embodiment of the present invention, the force acting between the active material and the adhesive film is an adhesion effect.

In the embodiment of the invention, the thickness of the lithium ion battery pole piece is 1 mm-3 mm, such as 1.2mm, 1.4mm, 1.5mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.4mm, 2.5mm, 2.6mm or 2.8 mm. The porosity of the lithium ion battery pole piece is 70% -90%, such as 72%, 75%, 78%, 80%, 82%, 85% or 88%.

In an embodiment of the present invention, the active material includes a positive electrode active material or a negative electrode active material.

In an embodiment of the present invention, the negative active material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, a silicon/carbon composite, and a silicon/oxygen/carbon composite. The silicon/carbon composite can be a carbon-coated composite material or a composite obtained by doping carbon with silicon; the silicon/oxygen/carbon composite may be a composite material in which silicon and carbon are bonded to each other through an oxygen-containing functional group (or oxygen atom).

In an embodiment of the present invention, the positive electrode active material includes any one of lithium iron phosphate, doped lithium iron phosphate, lithium cobaltate, doped lithium cobaltate, lithium nickelate, doped lithium nickelate, lithium manganate and doped lithium manganate or a combination of at least two of them.

The doping elements in the doped lithium iron phosphate, the doped lithium cobalt oxide, the doped lithium nickel oxide and the doped lithium manganese oxide are not limited, and can be selected by a person skilled in the art according to actual needs.

In the embodiment of the invention, in the lithium ion battery pole piece, the content of the adhesive film is 1 wt% to 10 wt%, for example, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%.

In an embodiment of the present invention, in the lithium ion battery electrode sheet, the content of the current collector is 5 wt% to 30 wt%, for example, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, or the like.

In the embodiment of the invention, in the lithium ion battery pole piece, the content of the active material is 50 wt% to 90 wt%, for example, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, or 85 wt%.

In the embodiment of the invention, in the lithium ion battery pole piece, the content of the conductive agent is 2 wt% to 8 wt%, for example, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or the like.

In a second aspect, the present invention provides a method for preparing a lithium ion battery pole piece, comprising the following steps:

dipping the current collector in the bonding solution to form a bonding film to obtain a modified current collector;

and dipping the modified current collector into electrode slurry to obtain the lithium ion battery pole piece.

In an embodiment of the present invention, the preparation process of the binding solution includes: and mixing the dopamine hydrochloride solution with a phosphoric acid buffer solution, and adjusting the pH value of the solution to obtain the bonding solution.

In the embodiment of the invention, the composition of the dopamine hydrochloride solution is the aqueous solution of dopamine hydrochloride; the composition of the phosphoric acid buffer solution in the invention is NaH₂PO₄And Na₂HPO₄The mixed aqueous solution of (1). The concentration of the phosphoric acid buffer solution is 0.02mol/L to 0.2mol/L, for example, 0.03mol/L, 0.05mol/L, 0.06mol/L, 0.08mol/L, 0.1mol/L, 0.12mol/L, 0.15mol/L, 0.16mol/L, or 0.18 mol/L. The pH value of the phosphoric acid buffer solution is 8.0-9.0, such as 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8 or 8.9. The concentration of the dopamine hydrochloride solution is 0.1mg/mL to 5mg/mL, for example, 0.2mg/mL, 0.5mg/mL, 0.8mg/mL, 1mg/mL, 1.5mg/mL, 1.8mg/mL, 2mg/mL, 2.5mg/mL, 2.8mg/mL, 3mg/mL, 3.5mg/mL, 4mg/mL, or 4.5 mg/mL. The conditioning solution pThe pH value after the H value is 8.2-8.6, such as 8.3, 8.4 or 8.5, and the pH value is less than or greater than 8.2-8.6, which are not beneficial to polymerization and film formation of dopamine.

In an embodiment of the present invention, the operation after the pH of the solution is adjusted may be stirring, the stirring time is 0.5 to 4 hours, for example, 0.8 hour, 1 hour, 1.5 hour, 2 hours, 2.5 hours, 3 hours, or 3.5 hours, and the stirring speed is 500 to 1000rpm, for example, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm, 800rpm, 850rpm, 900rpm, or 950 rpm.

In an embodiment of the invention, the porosity of the current collector is 70% to 90%, for example, 72%, 75%, 76%, 78%, 80%, 82%, 85%, 86%, or 88%, and the thickness of the current collector is 1 to 3mm, for example, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, or 2.8 mm. In one embodiment of the invention, the selected current collector is polyurethane foam, the porosity of the current collector is 70% -90%, the porosity is too low, the continuous permeability of a three-dimensional porous structure of the current collector is reduced, and the current collector is not beneficial to the full infiltration of electrolyte and the transmission of ions; the porosity is too high and the amount of slurry that can be attached is reduced, resulting in a reduction in specific energy.

In an embodiment of the present invention, the process of forming the adhesive film includes: and immersing the current collector in the bonding solution, taking out, and repeatedly performing the immersing and taking-out processes for 2-5 times (for example, 2 times, 3 times, 4 times or 5 times), wherein the immersing time is 0.5-2 h, for example, 0.6h, 0.7h, 0.8h, 1h, 1.2h, 1.5h or 1.8 h. The process can effectively remove air in the current collector, so that the formed bonding film is more uniform.

In an embodiment of the present invention, after the forming process of the adhesive film, a process of drying the current collector obtained after the dipping is further included. The drying is vacuum drying, and the drying is carried out for 4h to 8h, such as 4.5h, 5h, 5.5h, 6h, 6.5h, 7h or 7.5h, at the temperature of 60 ℃ to 80 ℃ (such as 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃ or 78 ℃ and the like).

In the embodiment of the invention, the method further comprises a pretreatment process of the current collector, wherein the pretreatment process can fully remove oil stains and certain impurities on the current collector.

In an embodiment of the present invention, the pretreatment process includes: the current collector is soaked in an alkaline solution and then washed with deionized water. The alkaline solution comprises NaOH solution and Na₂CO₃Solution and NaHCO₃At least one of the solutions. The concentration of the alkaline solution is 2 wt% to 10 wt%, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%, etc. The soaking time is 20min to 60min, such as 25min, 30min, 35min, 40min, 45min, 50min or 55 min.

In an embodiment of the present invention, a preparation method of the electrode paste comprises: and mixing a solvent, a dispersant, a conductive agent and an active substance to obtain the electrode slurry.

In an embodiment of the present invention, the mass ratio of the active material, the conductive agent, and the dispersant is (85 to 95): (3 to 10): 1 to 5, for example, 85:10:5, 95:4:1, 95:3:2, 90:8:2, 92:7:1, 91:8:1, 93:6:3, or 91:7: 3. The dispersing agent comprises at least one of sodium alginate, sodium carboxymethyl cellulose, PVDF and polyacrylic acid.

In the embodiment of the present invention, when the active material is a negative electrode active material, the particle diameter D90 of the negative electrode active material is not more than 30 μm, for example, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, or 28 μm.

In the embodiment of the present invention, when the active material is a positive electrode active material, the particle diameter D90 of the positive electrode active material is not more than 20 μm, for example, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, or the like.

The particle size D90 of the positive active material and the negative active material is selected to be within the range of the invention, so that the excellent technical effect can be achieved, the viscosity of the bonding film in the three-dimensional framework is reduced due to too large particle size, and the wrapping and connection of the conductive agent on the surface of the bonding film can be weakened, so that the loading capacity and the conductivity of the active material are influenced.

In an embodiment of the invention, the solvent comprises at least one of water and NMP.

In an embodiment of the present invention, the solvent, the dispersant, the conductive agent, and the active material are mixed by at least one of ultrasonic dispersion and stirring. The power of the ultrasonic dispersion is 500W-1000W, such as 600W, 700W, 800W or 900W. The ultrasonic dispersion time is 0.5 h-2 h, such as 0.6h, 0.8h, 1h, 1.2h, 1.4h, 1.5h, 1.6h or 1.8 h.

In an embodiment of the present invention, when the electrode slurry is a negative electrode slurry, the viscosity of the negative electrode slurry is 2000mPa · s to 6000mPa · s, for example 2500mPa · s, 3500mPa · s, 4500mPa · s, 5500mPa · s, or the like.

In an embodiment of the present invention, when the electrode slurry is a positive electrode slurry, the viscosity of the positive electrode slurry is 4000 to 8000mPa · s, for example, 4500, 5500, 6500 or 7500mPa · s.

The viscosity of the negative electrode slurry is 2000-6000 mPa.s, the viscosity of the positive electrode slurry is 4000-8000 mPa.s, the viscosity is too high, and the slurry is too viscous, so that the adhesion is not uniform; if the viscosity is too low, the slurry is too diluted to be easily adhered or the amount of adhesion is too small. The active material in the slurry is a negative electrode active material, and the obtained slurry is negative electrode slurry; the active material in the slurry is the anode active material, and the obtained slurry is the anode electrode slurry.

In an embodiment of the present invention, the solid content of the negative electrode slurry is 40 wt% to 50 wt%, for example, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, or the like.

In an embodiment of the present invention, the solid content of the positive electrode slurry is 50 wt% to 80 wt%, for example, 52 wt%, 55 wt%, 58 wt%, 60 wt%, 62 wt%, 65 wt%, 70 wt%, 75 wt%, 78 wt%, or the like.

In an embodiment of the present invention, the modified current collector is immersed in the electrode slurry for 0.5h to 4h, for example, 0.6h, 0.8h, 1h, 1.5h, 2h, 2.5h, 3h, or 3.5 h.

In the embodiment of the invention, after the modified current collector is immersed in the electrode slurry, the method further comprises the steps of taking out the obtained current collector, drying, rolling and slicing. The drying temperature is 50 ℃ to 70 ℃, such as 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃ or 68 ℃ and the like. The drying time is 4h to 8h, such as 4.5h, 4.8h, 5h, 5.5h, 6h, 6.5h, 7h or 7.5 h. The rolling pressure is 1MPa to 3MPa, for example, 1.2MPa, 1.5MPa, 1.8MPa, 2MPa, 2.2MPa, 2.5MPa or 2.8 MPa.

As a further preferable technical solution of the preparation method in the embodiment of the present invention, the preparation method of a lithium ion battery pole piece in the present invention includes the following steps:

(1) mixing a dopamine hydrochloride solution with the concentration of 0.1-5 mg/mL and a phosphoric acid buffer solution with the concentration of 0.02-0.2 mol/L, adjusting the pH value of the solution to 8.2-8.6, stirring at the speed of 500-1000 rpm for 0.5-4 h, wherein the pH value of the phosphate buffer solution is 8.0-9.0 to obtain a bonding solution, then soaking a current collector with the porosity of 70-90% and the thickness of 1-3 mm in the bonding solution, then taking out, repeatedly soaking and taking out for 2-5 times, wherein the soaking time is 0.5-2 h each time, and drying at the temperature of 60-80 ℃ for 4-8 h to obtain a modified current collector;

(2) mixing a dispersing agent, a conductive agent and a negative active substance according to the mass ratio of the negative active substance with the particle size D90 of less than or equal to 30 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain negative electrode slurry with the viscosity of 2000-6000 mPa & s and the solid content of 40-50 wt%;

or mixing the dispersing agent, the conductive agent and the positive active substance according to the mass ratio of the positive active substance with the particle size D90 of less than or equal to 20 mu m to (85-95) to (3-10) to (1-5), and performing ultrasonic dispersion with the power of 500-1000W for 0.5-2 h to obtain positive electrode slurry with the viscosity of 4000-8000 mPa & s and the solid content of 50-80 wt%;

(3) and dipping the modified current collector in the negative electrode slurry or the positive electrode slurry for 0.5-4 h, then taking out, drying at the temperature of 50-70 ℃ for 4-8 h, and performing rolling and slicing processes under the pressure of 1-3 MPa to obtain the lithium ion battery pole piece.

In a third aspect, an embodiment of the present invention further provides a lithium ion battery, where the lithium ion battery includes the lithium ion battery electrode sheet of the first aspect.

In the embodiment of the invention, the lithium ion battery comprises a positive pole piece and a negative pole piece.

In an embodiment of the present invention, the positive electrode plate is the lithium ion battery plate described in the first aspect.

In an embodiment of the present invention, the negative electrode plate is the lithium ion battery electrode plate described in the first aspect.

Compared with the prior art, the invention has the following beneficial effects:

(1) the lithium ion battery pole piece of the invention replaces the traditional current collector (copper foil and aluminum foil) with the current collector with the three-dimensional porous reticular framework structure, the three-dimensional porous reticular framework structure can effectively increase the contact area with the electrolyte, so that the electrolyte is more fully infiltrated, the distribution of the supported active substances on the three-dimensional space also reduces the ion transmission path in the charging and discharging process, and no binder is needed, the formed binding film has good adhesiveness and stickiness, the active substances can be fully adhered to the three-dimensional framework of the current collector, and the dispersion of active sites on the space and the improvement of the conductivity are facilitated.

(2) The lithium ion battery pole piece disclosed by the invention has the advantages of good flexibility and thermodynamic stability, good processing performance, simple preparation process, good compatibility with the existing sheet-making process and contribution to industrial production.

(3) The conductive agent in the lithium ion battery pole piece contains graphene oxide, so that excellent electrochemical performance can be obtained, and the conductivity of the three-dimensional framework is further enhanced because the carboxyl on the graphene oxide can perform a cross-linking reaction with the amino group on the binding film.

The following are typical but non-limiting examples of the invention: