阅读说明：本技术 一种锂电池正极的制备工艺及包含该正极的锂电池 (Preparation process of lithium battery anode and lithium battery comprising same ) 是由 林曹平 马祖华 刘瑞瑞 于 2019-09-16 设计创作，主要内容包括：本发明属于锂电池的制备技术领域,涉及一种锂电池正极的制备工艺及包含该正极的锂电池。所述制备工艺包括以下步骤：a)将金属带沿纵向冲制出无规则丝状孔,并沿横向进行拉伸,碾压后制得含有无规则丝状孔的金属网；b)金属网经清洗干燥后,依次采用5W以下激光、500-1000W激光和10-100W激光处理金属网表面；c)将制备好的正极浆料涂覆在经激光表面处理过的金属网上,烘干、压制、裁剪得到电池正极。本发明通过拉无规则丝状孔和多次激光处理,提高金属网的导电性以及提高正极材料与金属网的粘附性。(The invention belongs to the technical field of preparation of lithium batteries, and relates to a preparation process of a lithium battery anode and a lithium battery comprising the lithium battery anode. The preparation process comprises the following steps: a) Punching a metal belt into irregular filiform holes along the longitudinal direction, stretching along the transverse direction, and rolling to obtain a metal net containing the irregular filiform holes; b) After cleaning and drying the metal net, sequentially adopting a laser below 5W, a laser of 500-1000W and a laser of 10-100W to treat the surface of the metal net; c) And coating the prepared anode slurry on a metal mesh subjected to laser surface treatment, drying, pressing and cutting to obtain the battery anode. According to the invention, through drawing random filamentous holes and multiple laser treatments, the conductivity of the metal mesh is improved, and the adhesion of the anode material and the metal mesh is improved.)

1. The preparation process of the lithium battery positive electrode is characterized by comprising the following steps of:

a) Punching a metal belt into irregular filiform holes along the longitudinal direction, stretching along the transverse direction, and rolling to obtain a metal net containing the irregular filiform holes;

b) After cleaning and drying the metal net, sequentially adopting a laser below 5W, a laser of 500-1000W and a laser of 10-100W to treat the surface of the metal net;

c) And coating the prepared anode slurry on a metal mesh subjected to laser surface treatment, drying, pressing and cutting to obtain the battery anode.

2. The preparation process of claim 1, wherein the metal is one of stainless steel, platinum, aluminum, nickel, copper and stainless steel nickel plating, and the thickness of the rolled metal mesh is 0.05-0.15mm.

3. The process of claim 1, wherein the metal strip is longitudinally punched to have a random filiform pore volume of 60-85% of the total volume of the metal strip; after transverse stretching, the volume of the random filiform pore is 80-92% of the total volume of the metal strip.

4. The process according to claim 1, wherein the laser beam is set at 5W or less and the scanning speed is 500-1000mm/s;500-1000W laser, and the scanning speed is 400-800mm/s;10-100W laser, and the scanning speed is 50-100mm/s.

5. The preparation process according to claim 1, wherein the conductive carbon material with an average particle size of 300-500nm is sprayed on the surface of the metal mesh for the first time before the positive electrode slurry is coated on the metal mesh after the metal mesh subjected to the laser surface treatment, the conductive carbon material with an average particle size of 10-50nm is sprayed on the surface of the metal mesh for the second time after the metal mesh is dried, and then the slurry coating process is performed after the metal mesh subjected to the laser surface treatment is dried.

6. The process according to claim 5, wherein the first spray thickness is 3 to 7 μm and the second spray thickness is 2 to 5 μm.

7. The preparation process according to claim 1, wherein the positive electrode slurry comprises pyrite, a conductive agent, a binder and a solvent, and the mass percentages of the pyrite, the conductive agent, the binder and the solvent are respectively as follows: 65-75% of pyrite, 2-5% of conductive agent, 2-5% of binder and 20-30% of solvent.

8. The preparation process according to claim 7, wherein the conductive agent is one or more of acetylene black, graphite, ketjen black, carbon fiber and carbon nanotube.

9. The preparation process of claim 7, wherein the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, sodium carboxymethylcellulose, polyacrylonitrile and polyacrylate.

10. A lithium battery, comprising a positive electrode, a negative electrode, an electrolyte, a diaphragm and a shell, wherein the positive electrode is prepared by the process of claim 1, and the negative electrode is a metal sheet or a metal mesh made of metallic lithium or alloy lithium.

Technical Field

The invention belongs to the technical field of preparation of lithium batteries, and relates to a preparation process of a lithium battery anode and a lithium battery comprising the lithium battery anode.

Background

With the development of products such as electronic technology, communication products, digital products, small-sized test instruments and the like, the development of used power supply products is directly influenced. Chemical sources of electrical energy, commonly referred to as batteries, are widely used. The development trend of electronic and digital technologies is gradually towards miniaturization, multi-functionalization and portability, so that the power battery is also required to have high specific energy, high specific power, long service life and convenient use. The primary dry battery has small volume, is convenient to carry, use and replace, and is widely applied.

The dry batteries of the primary batteries are various, and the dry batteries of the primary batteries are commonly alkaline zinc-manganese batteries, common zinc-manganese batteries, zinc-silver batteries, zinc-air batteries, lithium-manganese batteries, lithium-iron batteries and the like. In daily life, alkaline zinc-manganese batteries and common zinc-manganese batteries are most widely used. However, the common zinc-manganese battery and the alkaline zinc-manganese battery cannot meet the requirements of some electrical appliances in the aspects of discharge platform, discharge stability, battery storage, heavy load work and the like, and the lithium-iron disulfide battery can better make up the defects.

The lithium-iron disulfide battery is a primary lithium primary battery, cubic pyrite is used as a positive active material, and lithium metal is used as a negative active material. Compared with the batteries of the same type, the lithium-iron disulfide battery has large specific capacity of quality and specific capacity of volume; the battery has high capacity, high discharge platform, stable discharge, wide application temperature range and good storage performance, the nominal voltage of the lithium-iron disulfide battery is 1.5V, and the lithium-iron disulfide battery can be interchanged with the alkaline zinc-manganese and carbon-zinc primary batteries widely applied in the market at present, so the lithium-iron disulfide battery can be widely applied to instruments and meters such as cameras, MP3, hearing aids, walkman, video cameras, industrial PC machines, computer RAM, CMOS circuit memory supporting power supplies, radio communication, various military communication radio stations, medical equipment, portable communication equipment, timers, counters and the like.

As a lithium primary battery, a lithium-iron disulfide battery has many advantages, but the manufacturing process thereof is complicated, particularly, the manufacturing process of the positive electrode of the battery. At present, the anode of the lithium-iron disulfide battery is mainly manufactured by mixing active substances into slurry, coating the slurry on an aluminum foil, drying the aluminum foil and manufacturing a pole piece. The process has the defects that the positive plate is easy to have a tape breakage phenomenon when being coated with slurry, the adhesion performance of the positive active material and the current collector is low, and the positive active material can fall off from the surface of the current collector in the storage or use process, so that the performance of the battery is influenced. In addition, in the long-time storage process of the coated positive electrode, under the condition of contacting with water and air, the positive active material can corrode the aluminum foil, so that the positive plate becomes brittle, the manufacturing of the battery is influenced, and the possibility of manufacturing the battery by the plate is lost under the severe condition

Disclosure of Invention

Aiming at the defects of the lithium battery in the prior art, the invention provides a preparation method of the lithium battery anode, which improves the bonding property of the anode active material and the metal mesh by drawing irregular filamentous holes and carrying out laser treatment for many times. And provides a lithium battery prepared by the anode, and the electrochemical performance of the lithium battery is improved.

One purpose of the invention is realized by the following technical scheme:

a preparation process of a lithium battery positive electrode comprises the following steps:

a) Punching a metal belt into irregular filiform holes along the longitudinal direction, stretching along the transverse direction, and rolling to obtain a metal net containing the irregular filiform holes;

b) After cleaning and drying the metal net, sequentially adopting a laser below 5W, a laser of 500-1000W and a laser of 10-100W to treat the surface of the metal net;

c) And coating the prepared anode slurry on a metal mesh subjected to laser surface treatment, drying, pressing and cutting to obtain the battery anode.

Preferably, the metal is one of stainless steel, platinum, aluminum, nickel, copper and stainless steel nickel plating, and the thickness of the metal mesh after rolling is 0.05-0.0.15mm.

Preferably, the metal strip is punched in the longitudinal direction to form a random filamentous pore volume of 60-85% of the total volume of the metal strip; after transverse stretching, the random filiform pore volume is 80-92% of the total volume of the metal strip.

Preferably, the scanning speed of the laser is 500-1000mm/s under 5W; 500-1000W laser, and the scanning speed is 400-800mm/s;10-100W laser, and the scanning speed is 50-100mm/s.

Preferably, before coating the slurry on the metal mesh subjected to the laser surface treatment, the conductive carbon material with the average particle size of 300-500nm is firstly sprayed on the surface of the metal mesh, after drying, the conductive carbon material with the average particle size of 10-50nm is sprayed on the surface of the metal mesh for the second time, and after drying, the slurry coating process is carried out.

Preferably, the first spraying thickness is 3-7 μm, and the second spraying thickness is 2-5 μm.

Preferably, the positive electrode slurry comprises a positive electrode active material, a conductive agent, a binder and a solvent, wherein the positive electrode active material, the conductive agent, the binder and the solvent respectively comprise the following components in percentage by mass: 65-75% of positive electrode active material, 2-5% of conductive agent, 2-5% of binder and 20-30% of solvent.

Preferably, the positive electrode active material is pyrite.

Preferably, the conductive agent is one or more of acetylene black, graphite, ketjen black, carbon fiber and carbon nanotube.

Preferably, the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, sodium carboxymethyl cellulose, polyacrylonitrile and polyacrylate.

The other purpose of the invention is realized by the following technical scheme:

a lithium battery comprises a positive electrode, a negative electrode, electrolyte, a diaphragm and a shell, wherein the positive electrode is prepared by the process, and the negative electrode is a metal sheet or a metal mesh made of metal lithium or alloy lithium.

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

1. the metal mesh adopted by the invention is a random filamentous hole, when the positive electrode slurry is coated on the metal mesh, the positive electrode active substances are mutually bonded together through the filamentous holes in the metal mesh and are embedded with the metal framework, so that the bonding property between the positive electrode materials and the metal framework is effectively improved; the random filamentous pores formed in the longitudinal direction make it easier for the slurry to be pressed into the gaps of the wire, and the wire coated with the slurry is more ductile and tough.

2. The method adopts laser with the power below 5W to remove the oil film of the metal net, exposes the oxide layer on the surface of the metal net after the oil film is removed, then uses 500-1000W laser to remove the oxide layer, then adopts 10-100W laser to form tiny pockmarked pits on the surface of the metal net, cleans up the oil stain and the oxide layer on the surface of the metal net through the sequential laser treatment, roughens the surface, improves the conductivity of the metal net and improves the adhesion of a positive electrode material and the metal net.

3. According to the invention, two conductive carbon films with different particle sizes are sprayed on the surface of the metal mesh, the average particle size of the conductive carbon material adopted in the second spraying process is obviously smaller than that of the conductive carbon film sprayed at the first time, the gap of the conductive carbon layer formed by the first spraying can be filled, a compact conductive protection layer is formed, the positive active material and the metal mesh are further isolated, the particle sizes of the conductive carbon materials sprayed at the two times are different, a rough surface is formed on the metal mesh, and the improvement of the binding force of the positive slurry and the metal mesh is facilitated.

Drawings

FIG. 1 is a schematic view of a metal strip of the present invention punched with irregular thread-like holes along the longitudinal direction;

FIG. 2 is a schematic diagram of transverse stretching of a random filamentous pore metal mesh provided by the present invention;

FIG. 3 is a schematic diagram of a random wire hole metal mesh according to the present invention after laser processing;

fig. 4 is a schematic diagram of the irregular filamentous pore metal mesh surface sprayed with the conductive carbon material provided by the present invention.

Detailed Description

Hereinafter, embodiments will be described in detail with respect to a process for preparing a positive electrode for a lithium battery of the present invention and a lithium battery using the same, however, the embodiments are exemplary and the present disclosure is not limited thereto. And the drawings used herein are for the purpose of illustrating the disclosure better and are not intended to limit the scope of the invention.

In some embodiments of the present invention, the process for preparing the lithium battery positive electrode comprises the following steps:

a) Punching a metal belt into irregular filiform holes along the longitudinal direction, stretching along the transverse direction, and rolling to obtain a metal net containing the irregular filiform holes;

b) After cleaning and drying the metal net, sequentially adopting a laser below 5W, a laser of 500-1000W and a laser of 10-100W to treat the surface of the metal net;

c) Coating the prepared anode slurry on a metal mesh subjected to laser surface treatment, drying, pressing and cutting to obtain a battery anode; the positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, and a solvent.

In the present invention, the winding direction of the metal mesh during the battery production process is defined as the longitudinal direction, and the direction perpendicular to the longitudinal axis is defined as the transverse direction. The metal band which is cleaned, decontaminated and cut into a proper shape is punched with irregular filiform holes along the longitudinal direction, as shown in figure 1, the hole-shaped structure is in a thread shape, extends along the longitudinal direction and is arranged in an irregular manner. The longitudinal flexibility of the metal mesh can be better improved due to the longitudinal extension of the filiform hole, and when the battery is manufactured, the active substances of the positive plate containing certain positive active substances are not easy to fall off when the positive plate is wound because the winding direction of the battery pole piece manufactured by the metal mesh is consistent with the longitudinal direction of the filiform hole of the metal mesh. The stretching is then carried out in the transverse direction, as shown in fig. 2, to maintain a certain size of expansion of the filamentous pores in the transverse direction. After transverse stretching, the occupied volume of the filamentous holes is further enlarged, the mechanical property of the metal mesh is improved, and the formed metal mesh has better tensile strength and toughness, is not easy to deform and is beneficial to ensuring the product quality of the battery. And then, carrying out rolling treatment on the metal mesh to obtain the metal mesh with a certain thickness, and ensuring the consistency of the thickness of the metal mesh by a rolling means, thereby being more beneficial to the uniformity and consistency of the anode slurry coating in the later period.

According to the metal mesh with the irregular filiform holes, when the positive electrode slurry is coated, the positive electrode active substances are mutually bonded through the filiform holes in the metal mesh and are embedded with the metal framework, so that the bonding property between the positive electrode materials and the metal framework is effectively improved. From the viewpoint of material coating, the mutual adhesion of the positive electrode active materials in the pores imposes less requirements on the material of the coated substrate, and the coating layer can be thicker. While an increase in the thickness of the coating layer has conventionally necessarily resulted in a decrease in the adhesion of the coating layer to the coated substrate, the use of such pore bonding can increase the thickness of the coating layer without a significant decrease in adhesion, resulting in an increase in the capacity of the battery.

Compared with the shape of rhombus, circle, rectangle or cross which is regularly arranged on the metal net in the prior art, the irregular filiform hole structure formed by the metal net of the invention has the advantages that when the positive electrode slurry is filled, the slurry is easier to press into the gaps of the metal net, and the metal net coated with the slurry has better ductility and toughness.

Cleaning the surface oil layer of the rolled metal net by using a solution containing a surfactant, wherein the surfactant is any surfactant capable of removing oil stains, the cleaning mode can be a dipping cleaning method or a spraying cleaning method, the cleaning time is 2-10min, and stains generated on the surface of the metal net in the processing process are removed. And then treating the surface by adopting laser with different intensities, firstly treating by adopting the laser with the power of less than 5W, wherein the scanning speed of the laser is preferably 500-1000mm/s, the oil stains attached to the outer surface of the metal mesh in the processing process are difficult to remove only by using a surfactant, and the oil stains attached to the surface can be effectively removed by adopting the laser treatment with low intensity. And then further processing the surface of the metal mesh by adopting laser with the power of 500-1000W, wherein the scanning speed of the laser is preferably 400-800mm/s, and removing a thin oxide layer generated on the surface of the outer surface of the metal mesh in the high-temperature processing process so as to reduce the surface resistance of the metal mesh. Finally, the surface is ablated by using laser with the power of 10-100W, the scanning speed of the laser is preferably 50-100mm/s, the outer surface of the metal mesh of the wiredrawing hole is ablated into tiny pockmark-shaped pits, as shown in figure 3, and figure 3 is a simulation diagram of the tiny pockmark-shaped pits on the surface of the metal mesh, so that the surface roughness Ra of the metal mesh is more than 5 μm (Ra represents the average value of the absolute values of the distances from each point on the surface profile of the metal mesh to the line in the profile within the sampling length of 10 mm). The surface of the metal net is roughened, so that the contact area between the positive active material and the metal net is increased, the resistance of a material combination part is reduced, and meanwhile, the combination strength of the positive active material and the metal net is improved. In the 3 laser processing procedures, the parameters were the same except for the power and scanning speed.

The invention adopts the laser surface treatment process with different intensities in sequence, the sequence can not be changed, the oxide layer on the surface of the metal mesh can be exposed only by removing the oil film by adopting laser with the power of less than 5W, then the oxide layer is removed by using laser with the power of 500-1000W, and then the tiny pit shaped like a pit is formed on the surface of the metal mesh by adopting laser with the power of 10-100W. Through the laser treatment of the invention, oil stains, oxide layers and the like on the surface of the metal mesh are cleaned, and the surface is roughened, so that the conductivity of the metal mesh is improved, and the adhesion of the anode material and the metal mesh is improved.

And finally, conveying the uniformly stirred anode slurry to a coating machine to be coated on a metal mesh, drying and pressing the metal mesh coated with the anode substance, preferably, the thickness of the metal mesh is 0.2-0.6mm, and then cutting, welding lugs and the like to prepare the anode plate.

In a preferred embodiment of the invention, the metal is one of stainless steel, platinum, aluminum, nickel, copper and stainless steel nickel plating, and the thickness of the metal mesh after rolling is 0.05-0.15mm. The thickness of the expanded metal after rolling is further preferably 0.08mm.

In a preferred embodiment of the invention, the metal strip is longitudinally punched with a random filiform pore volume of 60 to 85%, preferably around 70%, of the total volume of the metal strip; after transverse stretching, the volume of the random filiform pores is 80-92%, preferably about 90%, of the total volume of the metal strip.

In a preferred embodiment of the present invention, before coating the positive electrode slurry on the metal mesh subjected to the laser surface treatment, the conductive carbon material with the average particle size of 300-500nm is firstly sprayed on the surface of the metal mesh for the first time, after drying, the conductive carbon material with the average particle size of 10-50nm is sprayed on the surface of the metal mesh for the second time, and after drying, the slurry coating process is performed.

The term "particle diameter" as used herein means a value at which the distance between 2 arbitrary points on the contour line of the material particles observed by an observation device such as SEM or TEM is the largest. The "average particle diameter" refers to an average value calculated as the particle diameter of material particles observed in several to several tens of fields of view using an observation device such as SEM or TEM.

The conductive carbon material is sprayed on the metal mesh, so that the internal resistance of the metal mesh can be reduced, the conductivity of the material can be improved, the formed conductive carbon layer effectively isolates the direct contact between the positive active material and the metal mesh, the risk that the positive active material corrodes an aluminum foil is reduced, and the possibility that the electrolyte corrodes the metal mesh in the use process of the battery is also reduced. The conductive carbon material with the average particle size of 10-50nm adopted in the second spraying process can fill the gaps of the conductive carbon layer formed by the first spraying to form a compact conductive protective layer, further isolate the positive active material from the metal mesh, and also can protect the surface of the metal mesh from being oxidized when the positive electrode is subjected to high-temperature treatment, and the conductive carbon materials sprayed twice have different particle sizes to form a rough surface on the metal mesh, thereby being beneficial to improving the bonding force of the positive slurry and the metal mesh. The conductive carbon material is preferably conductive graphite or conductive carbon black.

The spraying mode of the conductive carbon material on the metal net is preferably as follows: an emulsion liquid composed of a conductive carbon material, a surfactant, a binder and a solvent is subjected to ultrasonic spraying to form a uniform carbon film layer on the surface of the metal mesh.

The conductive carbon material, the surfactant, the binder and the solvent respectively comprise the following components in percentage by mass: 50-80% of conductive carbon material, 1-5% of surfactant, 1-5% of binder and 15-40% of solvent.

The surfactant is exemplified by cetyltrimethylammonium bromide, sodium hexadecylsulfonate, sodium dodecylbenzenesulfonate, polyethylene glycol-400 and the like, the binder is exemplified by polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethylcellulose, polyacrylonitrile and the like, and the solvent is exemplified by N, N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and the like. The above components are merely examples, and the present invention is not limited thereto.

In a preferred embodiment of the present invention, the thickness of the carbon film layer formed by the first spraying is 3-7 μm, and the thickness of the carbon film layer formed by the second spraying is 2-5 μm. The thickness of the carbon film layer can be controlled by the ejection amount and ejection speed of the emulsion liquid.

The schematic diagram of the irregular filiform hole metal net after the surface is sprayed with the conductive carbon material is shown in fig. 4, and the surface of the metal net except the filiform hole part is uniformly formed with the carbon film layer.

In a preferred embodiment of the present invention, the positive electrode active material is pyrite, and the mass percentages of the pyrite, the conductive agent, the binder and the solvent are: 65-75% of pyrite, 2-5% of conductive agent, 2-5% of binder and 20-30% of solvent. The components are uniformly mixed to prepare semi-dry slurry for coating.

The conductive agent is preferably one or more of acetylene black, graphite, ketjen black, carbon fiber and carbon nano tube. The binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, sodium carboxymethylcellulose, polyacrylonitrile and polyacrylate. Such solvents include, but are not limited to, N-methylpyrrolidone, acetone, isobutanol, tetrahydrofuran, dimethylsulfoxide, and the like.

In some embodiments of the present invention, there is also provided a lithium battery including a positive electrode, a negative electrode, an electrolyte, a separator and a housing, wherein the positive electrode is prepared by the above process, and the negative electrode is a metal sheet or a metal mesh made of lithium metal or lithium alloy. And (3) laminating and winding the positive electrode, the diaphragm, the negative electrode and the diaphragm together to form a battery core, putting the battery core into a battery shell, injecting electrolyte and sealing the battery shell to obtain the lithium battery.

The diaphragm is a polyethylene microporous diaphragm or a polypropylene microporous diaphragm, and the thickness of the diaphragm is 15-100 microns.

The electrolyte is formed of an electrolyte including, but not limited to, lithium iodide, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium bromide, lithium perchlorate, lithium hexafluorophosphate, etc., and an organic solvent including, but not limited to, propylene carbonate, ethylene carbonate, dimethoxyethane, dioxolane, sulfolane, etc.

Hereinafter, the technical solution of the present invention will be further described and illustrated by specific examples. However, these embodiments are exemplary, and the present disclosure is not limited thereto. Unless otherwise specified, the raw materials used in the following specific examples of the present invention are those commonly used in the art, and the methods used in the examples are those conventional in the art.