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CN-121983538-A - Negative electrode slurry, preparation method thereof, negative electrode plate and lithium ion battery

CN121983538ACN 121983538 ACN121983538 ACN 121983538ACN-121983538-A

Abstract

The invention relates to the technical field of lithium ion batteries, and particularly discloses negative electrode slurry, a preparation method thereof, a negative electrode plate and a lithium ion battery. The negative electrode slurry comprises silicon-based particles, a binder, a conductive agent and a solvent, wherein the surface of the silicon-based particles is provided with a g-C 3 N 4 electronic inert layer, and the binder is obtained by mixing polyacrylic acid and strong alkali lithium salt. Therefore, the negative electrode slurry can solve the aggregation problem of polyacrylic acid, further enhance the adhesion force between the silicon-based particles and the polymer binder, and promote Li + diffusion and further improve the dynamic performance by introducing the g-C 3 N 4 electronic inert layer on the surfaces of the silicon-based particles.

Inventors

  • WEI HAITAO
  • WANG YUNWEN
  • ZHU WEIHUA
  • Zhao Zhenshuai

Assignees

  • 湖北亿纬动力有限公司

Dates

Publication Date
20260505
Application Date
20260113

Claims (15)

  1. 1. The negative electrode slurry is characterized by comprising silicon-based particles, a binder, a conductive agent and a solvent; Wherein the surface of the silicon-based particle is provided with a g-C 3 N 4 electronic inert layer; the binder contains polyacrylic acid and a strong alkali lithium salt.
  2. 2. The negative electrode slurry of claim 1, wherein the strong base lithium salt comprises at least one of lithium hydroxide, lithium methoxide, lithium ethoxide; And/or the mass ratio of the strong alkali lithium salt to the polyacrylic acid is 1 (1.5-2.5).
  3. 3. The negative electrode slurry according to claim 1, wherein the mass ratio of the silicon-based particles, the binder, and the conductive agent is (6-8): 1-2.
  4. 4. The negative electrode slurry according to any one of claims 1 to 3, wherein the silicon-based particles comprise at least one of SiO x @ C, si/C, nano Si, siO, new silicon carbon; and/or the conductive agent comprises at least one of Super P, ketjen black, acetylene black and graphite; And/or the solvent is water.
  5. 5. A method of producing the negative electrode slurry according to any one of claims 1 to 4, characterized by comprising: first mixing the silicon-based particles to be treated with g-C 3 N 4 to obtain silicon-based particles; Secondly mixing polyacrylic acid and strong alkali lithium salt to obtain a binder; And thirdly mixing the silicon-based particles, the binder, the conductive agent and the solvent to obtain the negative electrode slurry.
  6. 6. The method of claim 5, wherein the first mixing of the silicon-based particles to be treated with g-C 3 N 4 is performed by: dispersing the silicon-based particles to be treated in a first solvent to obtain a first solution; Dispersing the g-C 3 N 4 in a second solvent to obtain a second solution; dropwise adding the first solution into the second solution, and stirring to obtain a compound; centrifuging the complex to obtain a precipitate, And washing, drying and heat treating the precipitate to obtain the silicon-based particles.
  7. 7. The method of claim 6, wherein the concentration of the silicon-based particles to be treated in the first solution is 0.004-0.006 g/mL; and/or, in the second solution, the concentration of the g-C 3 N 4 is 0.003-0.005g/mL; and/or, the first solvent and the second solvent are respectively selected from absolute ethyl alcohol.
  8. 8. The method of claim 5, wherein the second mixing of the polyacrylic acid and the strong alkali lithium salt is performed by: fourth mixing the strong alkali lithium salt with a third solvent to obtain a precursor solution; Fifth mixing the polyacrylic acid with a fourth solvent to obtain a polyacrylic acid solution; and (3) carrying out sixth mixing and stirring on the precursor solution and the polyacrylic acid solution to obtain the binder.
  9. 9. The method of claim 8, wherein the mass ratio of the strong alkali lithium salt is 4-6% based on the total mass of the precursor solution; And/or, based on the total mass of the polyacrylic acid solution, the mass ratio of the polyacrylic acid is 8-12%; and/or, the third solvent and the fourth solvent are respectively selected from water.
  10. 10. The method according to claim 5, wherein the solid content of the anode slurry is 48-54%.
  11. 11. A negative electrode active layer, characterized in that the negative electrode active layer comprises silicon-based particles, a binder and a conductive agent; Wherein the surface of the silicon-based particle is provided with a g-C 3 N 4 electronic inert layer; the binder contains polyacrylic acid and a strong alkali lithium salt.
  12. 12. The anode active layer according to claim 11, wherein the anode active layer is prepared using the anode slurry according to any one of claims 1 to 4 or the anode slurry obtained by the method according to any one of claims 5 to 10.
  13. 13. A negative electrode sheet comprising the negative electrode active layer according to any one of claims 11 to 12, wherein the negative electrode active layer is located on at least one side surface of a current collector.
  14. 14. A lithium ion battery comprising the negative electrode sheet of claim 13.
  15. 15. An electrical device comprising the lithium-ion battery of claim 14.

Description

Negative electrode slurry, preparation method thereof, negative electrode plate and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to negative electrode slurry and a preparation method thereof, a negative electrode plate and a lithium ion battery. Background Lithium Ion Batteries (LIBs) play a vital role in various applications such as electronic devices and electric vehicles due to their high energy density, high voltage, low self-discharge rate, and the like. Graphite is commonly used as the negative electrode material for LIB, but its capacity is limited to 372 mAh g -1, which limits the potential energy density of LIB. In contrast, silicon (Si) has attracted wide interest as a next-generation anode material because of its theoretical capacity as high as 4200 mAh g -1. However, a major disadvantage of silicon is that over 300% of the volume expansion occurs during repeated charge and discharge, and this significant expansion causes the silicon-based particles to pulverize and fall off the electrode, severely degrading the battery performance, and there is also a problem of poor kinetics for various reasons, directly postponing the commercial application of silicon-based negative electrodes. To solve these problems, strategies to enhance the adhesion between silicon-based particles and polymeric binders have been widely studied. The polymeric binder is critical to maintaining cohesion of the electrode components and to ensure adhesion of the active material to the current collector during operation of the battery. Among the numerous polymeric binders, polyacrylic acid (PAA) has become a binder of great interest in LIB silicon-based cathodes because of its high content of carboxyl groups (-COOH). These functional groups are effective in enhancing adhesion between the silicon-based particles, the conductive material, and the current collector, and inhibiting volumetric expansion of silicon during lithiation and delithiation by forming hydrogen bonds with the surface of the silicon-based particles. However, polyacrylic acid chains form random coil structures due to the presence of intra-chain hydrogen bonds between the-COOH groups. This phenomenon reduces the sites available for interaction with the silicon-based particles and leads to polymer aggregation. This aggregation may reduce the adhesion and capacity of the electrode, ultimately limiting the high performance of the silicon-based negative electrode in LIB. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, an object of the present invention is to provide a negative electrode slurry capable of solving the aggregation problem of polyacrylic acid, thereby enhancing the adhesion between silicon-based particles and a polymer binder, and simultaneously promoting Li + diffusion by introducing a g-C 3N4 electronic inert layer to the surface of the silicon-based particles, thereby improving the dynamic properties. Accordingly, in a first aspect of the present invention, the present invention proposes a negative electrode slurry. According to the embodiment of the invention, the negative electrode slurry comprises silicon-based particles, a binder, a conductive agent and a solvent, wherein the surface of the silicon-based particles is provided with a g-C 3N4 electronic inert layer, and the binder contains polyacrylic acid and strong alkali lithium salt. According to the invention, through blending treatment of the strong alkali lithium salt and the polyacrylic acid, the technical defect that the molecular chain of the polyacrylic acid is easy to aggregate is solved, so that the interfacial adhesion performance between the silicon-based particles and the polymer binder is remarkably enhanced, and the uniform dispersion of the binder system is realized. Specifically, OH - ions generated by dissociation of strong alkali lithium salt can be efficiently and fully neutralized with carboxyl (-COOH) on a polyacrylic acid molecular chain to generate carboxylic acid lithium groups (-COOLi), wherein the-COOLi groups are electronegative groups and can be stably anchored on a polyacrylic acid polymer chain, and as each-COOLi group on the chain carries the same negative charge, strong and durable electrostatic repulsive effect can be formed among the molecular chains. The electrostatic repulsive force can effectively counteract the action force of intra-chain hydrogen bonds between original-COOH groups in the polyacrylic acid molecular chains, so that the originally tightly curled polyacrylic acid molecular chains are forced to be stretched, on one hand, the uniform dispersion of the binder solution is realized, and on the other hand, the diffusion kinetic performance of lithium ions in the electrode can be improved through the existence of the-COOLi groups. In addition, the g-C 3N4 electron inert layer is in