CN-122025523-A - Surface modification method of silicon-carbon negative electrode material, modified silicon-carbon negative electrode material, negative electrode plate and lithium ion battery

CN122025523ACN 122025523 ACN122025523 ACN 122025523ACN-122025523-A

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a surface modification method of a silicon-carbon negative electrode material, a modified silicon-carbon negative electrode material, a negative electrode plate and a lithium ion battery. The surface modification method comprises the steps of mixing a silicon-carbon composite material with a carbon source, carrying out pyrolysis carbonization under an inert atmosphere to obtain an amorphous carbon coated silicon-carbon material, carrying out lithium salt gradient coating on the amorphous carbon coated silicon-carbon material, dispersing the lithium salt gradient coated silicon-carbon material in an NMP solution of PSI, carrying out dipping, filtering, drying, and then carrying out heat treatment under the inert atmosphere to obtain the modified silicon-carbon anode material. According to the invention, through lithium salt gradient coating and PSI modification, the dynamic performance of the silicon-carbon anode material is improved, and the surface of the silicon-carbon anode material is optimized, so that the electrochemical performance of a solid electrolyte interface is enhanced.

Inventors

JIA ZHILIN
SONG HE
LI XIANSHUAI
LU WEIQING
MA ZHEZHE
WANG FEI

Assignees

安徽得壹能源科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260331

Claims (10)

1. The surface modification method of the silicon-carbon anode material is characterized by comprising the following steps of: Mixing the silicon-carbon composite material with a carbon source, and carrying out pyrolysis carbonization in an inert atmosphere to obtain an amorphous carbon coated silicon-carbon material; carrying out lithium salt gradient coating on the amorphous carbon coated silicon carbon material; and dispersing the silicon-carbon material subjected to lithium salt gradient coating in an NMP solution of PSI, soaking, filtering, drying, and then performing heat treatment under inert atmosphere to obtain the modified silicon-carbon anode material.
2. The method according to claim 1, further comprising a step of pretreating the silicon-carbon composite material, specifically, drying the silicon-carbon composite material at 100-150 ℃ for 2-10 hours.
3. The method according to claim 1, wherein the carbon source is an organic carbon source, preferably glucose, sucrose or phenolic resin.
4. The method of claim 3, wherein the mass ratio of the silicon-carbon composite material to the carbon source is 1:0.05-0.3, or the inert atmosphere is argon or nitrogen.
5. The method according to claim 1, wherein the pyrolysis carbonization conditions are such that the temperature is raised to 500-700 ℃ at a rate of 2-5 ℃ per minute and kept for 2-5 hours, or such that the lithium salt is LiOH and LiCl, preferably the molar ratio of LiOH to LiCl is 3:1-3.
6. The method according to claim 1, wherein the soaking condition is that stirring is continuously carried out for 4-12 hours at 50-80 ℃, or the heat treatment condition is that heat treatment is carried out for 1-3 hours at 200-350 ℃, or the heat treatment further comprises washing with an organic solvent and drying operation, preferably one or more of DMF, DMSO, NMP, the drying operation is that vacuum drying is carried out for 6-10 hours at 80-110 ℃.
7. The modified silicon-carbon negative electrode material prepared by the surface modification method according to any one of claims 1 to 6.
8. A negative electrode sheet comprising a current collector and an active layer attached to the surface of the current collector, wherein the active material in the active layer is the modified silicon-carbon negative electrode material of claim 7.
9. The method for preparing a negative plate according to claim 8, wherein the modified silicon-carbon negative electrode material, the conductive agent, the binder and the thickener are added into a solvent and uniformly mixed to obtain slurry, and the slurry is coated on the surface of a current collector and dried to obtain the negative plate.
10. A lithium ion battery, wherein the negative electrode of the lithium ion battery is the negative electrode sheet of claim 8.

Description

Surface modification method of silicon-carbon negative electrode material, modified silicon-carbon negative electrode material, negative electrode plate and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a surface modification method of a silicon-carbon negative electrode material, a modified silicon-carbon negative electrode material, a negative electrode plate and a lithium ion battery. Background The information disclosed in the background of the invention is only for enhancement of understanding of the general background of the invention and is not necessarily to be taken as an admission or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art. The silicon-carbon negative electrode material has extremely high theoretical specific capacity (about 10 times of graphite), and has become a research hot spot for lithium ion battery negative electrode materials in recent years. However, silicon has poor intrinsic conductivity, and a Solid Electrolyte Interface (SEI) film formed during charge and discharge is unstable, which seriously hinders effective transmission of lithium ions, thereby resulting in poor material rate performance and short cycle life. Therefore, how to effectively improve the dynamic performance of the silicon-carbon anode material and construct a stable SEI film has become a key research direction for improving the electrochemical performance of the silicon-carbon anode material. Disclosure of Invention In view of the above, the invention provides a surface modification method of a silicon-carbon negative electrode material, a modified silicon-carbon negative electrode material, a negative electrode plate and a lithium ion battery. According to the invention, the silicon-carbon negative electrode material is subjected to surface modification, so that the dynamic performance of the silicon-carbon negative electrode material is improved, and the surface of the silicon-carbon negative electrode material is optimized, so that the electrochemical performance of a solid electrolyte interface is enhanced, the intercalation/deintercalation of lithium ions is promoted, and the modified silicon-carbon negative electrode-nickel cobalt lithium manganate full battery has excellent dynamic performance and long cycle life. In order to achieve the above object, the present invention is realized by the following technical scheme: In a first aspect, the invention provides a surface modification method of a silicon-carbon anode material, comprising the following steps: Mixing the silicon-carbon composite material with a carbon source, and carrying out pyrolysis carbonization in an inert atmosphere to obtain an amorphous carbon coated silicon-carbon material; carrying out lithium salt gradient coating on the amorphous carbon coated silicon carbon material; dispersing the silicon-carbon material coated by lithium salt gradient in N-methyl pyrrolidone (NMP) solution of Polysuccinimide (PSI), soaking, filtering, drying, and then performing heat treatment under inert atmosphere to obtain the surface modified silicon-carbon anode material. In some embodiments, the method further comprises a pretreatment step of the silicon-carbon composite material, specifically, drying the silicon-carbon composite material at 100-150 ℃ for 2-10 hours. The purpose of the pretreatment step is to thoroughly remove the adsorbed moisture from the surface. In some embodiments, the carbon source is an organic carbon source, preferably glucose, sucrose, or phenolic resin. The organic carbon source can be converted into amorphous carbon after pyrolysis, so that a plurality of uniform and compact coating layers can be formed, and the conductivity of the subsequent silicon-carbon material is improved to a certain extent. In some embodiments, the mass ratio of the silicon carbon composite material to the carbon source is 1:0.05-0.3. In some embodiments, the inert atmosphere is argon or nitrogen. In some embodiments, the pyrolysis carbonization conditions are elevated to 500-700 ℃ at a rate of 2-5 ℃ per minute and maintained for 2-5 hours. In some embodiments, the lithium salt gradient coating adopts an ethanol-assisted lithium salt gradient coating technology, the solvent is ethanol, the lithium salt is LiOH and LiCl, and preferably, the molar ratio of the LiOH to the LiCl is 3:1-3. The lithium salt solution of the ethanol is configured to coat the amorphous carbon coated silicon carbon material under negative pressure, so that a Li-O-C composite conductive network can be constructed on the surface layer and the subsurface layer of the silicon carbon inner layer carbon, the first coulomb efficiency can be improved, the interface impedance can be reduced, and the surface conductivity of the silicon carbon material can be improved, and preferably, the negative pressure is-0.05 to-0.1 MPa. In some embodim