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CN-122025598-A - Composite silicon negative electrode material, preparation method thereof and battery

CN122025598ACN 122025598 ACN122025598 ACN 122025598ACN-122025598-A

Abstract

The invention provides a composite silicon anode material, a preparation method thereof and a battery, wherein the composite silicon anode material comprises a silicon carbon material and an artificial SEI film coated on the surface of the silicon carbon material, the artificial SEI film comprises a polymer, and a monomer of the polymer contains triazole rings, mercaptan, alkenyl and nitro-substituted phenyl. According to the composite silicon anode material, the specific polymer is coated to serve as an artificial SEI film, and all functional groups in the polymer are synergistic, so that the material structure is expansion-resistant, the interface is firm, the high-temperature stability and the ion transmission are efficient, and the cycle performance, the multiplying power performance, the quick charge performance, the high-temperature performance and other performances of the battery are effectively improved.

Inventors

  • XIE YINGPENG
  • ZHAO RUIRUI
  • JI YAJUAN
  • LI WENTAO
  • XU XIAOXIA

Assignees

  • 惠州亿纬锂能股份有限公司

Dates

Publication Date
20260512
Application Date
20260313

Claims (10)

  1. 1. The composite silicon negative electrode material is characterized by comprising a silicon-carbon material and an artificial SEI film coated on the surface of the silicon-carbon material, wherein the artificial SEI film comprises a polymer, and the monomer of the polymer has the following structural formula: ; Wherein R 1 contains alkenyl, and R 2 contains phenyl substituted by nitro.
  2. 2. The composite silicon negative electrode material according to claim 1, wherein R 1 is selected from allyl or methyl substituted allyl; preferably, R 2 is selected from 3-nitrophenyl or 3-methyl-2-nitrophenyl.
  3. 3. The composite silicon negative electrode material according to claim 1 or 2, wherein the monomer of the polymer comprises And/or ; Preferably, the number average molecular weight of the polymer is controlled to be 9X 10 4 g/mol~3×10 7 g/mol; Preferably, the artificial SEI film has a thickness of 35 nm-130 nm; preferably, in the composite silicon anode material, the mass ratio of the artificial SEI film is 0.5-3 wt%.
  4. 4. The composite silicon negative electrode material according to claim 1 or 2, wherein the silicon carbon material has a particle diameter D50 of 4 μm to 9 μm and a specific surface area of 1m 2 /g~4m 2 /g; preferably, the silicon carbon material comprises silicon grains and a hard carbon material; preferably, the mass ratio of the silicon crystal grains to the hard carbon material is (0.4-1.2): 1.
  5. 5. The composite silicon negative electrode material according to claim 4, wherein the hard carbon material comprises micropores and mesopores; preferably, the pore diameter of the micropore is 0.8-1.5 nm, and the pore volume accounts for 20-40% of the total pore volume of the hard carbon material; Preferably, the pore diameter of the mesoporous is 5-20 nm, and the pore volume accounts for 60-80% of the total pore volume of the hard carbon material; Preferably, the size of the silicon crystal grains is 0.8 nm-2 nm.
  6. 6. A method for preparing the composite silicon negative electrode material according to any one of claims 1 to 5, comprising the steps of: Dispersing a polymer in a first organic solution to obtain a dispersion liquid, mixing the dispersion liquid with a silicon-carbon material to obtain a mixed slurry, and then carrying out spray drying on the mixed slurry to obtain the composite silicon anode material.
  7. 7. The preparation method according to claim 6, wherein the mass fraction of the polymer in the dispersion is 8wt% to 35wt%; Preferably, the temperature of the mixing is 30-100 ℃ and the time is 5-10 hours; preferably, the inlet temperature of the spray drying is 100-200 ℃, and the outlet temperature is 60-100 ℃.
  8. 8. The method of producing according to claim 6 or 7, wherein the method of producing the polymer comprises the steps of: Mixing a monomer of a polymer, a second organic solvent and an initiator, performing polymerization reaction to obtain a polymer solution, adding the polymer solution into a precipitation solvent, and then standing, washing and drying to obtain the polymer; Preferably, the temperature of the polymerization reaction is 60-110 ℃ and the time is 4-9 hours; Preferably, the standing time is 2-4 hours; preferably, in the mixed solution obtained by mixing the monomer of the polymer material, the second organic solvent and the initiator, the concentration of the monomer of the polymer is 0.8 mol/L-2.0 mol/L; Preferably, the addition amount of the initiator is 0.1-0.8 wt% of the monomer mass of the polymer; Preferably, the initiator comprises any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, or dibenzoyl peroxide; preferably, the first organic solvent and the second organic solvent each independently comprise any one or a combination of at least two of benzene, toluene, NMP or DMF; Preferably, the precipitation solvent includes any one or a combination of at least two of propanol, isopropanol or acetone.
  9. 9. A battery comprising the composite silicon negative electrode material of any one of claims 1-5.
  10. 10. The battery of claim 9, wherein the electrolyte of the battery comprises an additive comprising any one or a combination of at least two of LiTFSI, FEC and LiBOB; Preferably, in the electrolyte of the battery, the content of LiTFSI is 2-4wt%; Preferably, in the electrolyte of the battery, the content of FEC is 0.5-1.5 wt%; Preferably, in the electrolyte of the battery, the content of LiBOB is 0.2-0.5 wt%.

Description

Composite silicon negative electrode material, preparation method thereof and battery Technical Field The invention belongs to the technical field of batteries, and relates to a composite silicon anode material, a preparation method thereof and a battery. Background In the development process of new energy automobiles, the endurance mileage becomes a breakthrough in development bottleneck, so that a lithium ion battery with high energy density needs to be developed, and the development of a negative electrode material with high reversible specific capacity is one of key factors for breakthrough of the high energy density ion battery. Silicon materials are considered ideal negative electrode materials for lithium ion batteries because of their ultra-high theoretical capacity. However, since the silicon material has a great volume change during charge and discharge, the silicon material itself is broken, thereby causing rapid capacity decay, and the silicon material has insufficient oxidation resistance at high temperature, is subject to oxidative decomposition, and has low intrinsic conductivity. In the prior art, the expansion is relieved by coating an artificial SEI film on the surface of a silicon material, but the interface binding force of the existing coating material and the silicon material is weak, the SEI film is easy to fall off in the circulation process, the SEI film is invalid, the compactness and the stability are poor, the lithium ion transmission path is not smooth, the rate performance and the quick charging performance are insufficient, and meanwhile, the problem that the silicon material is easy to oxidize and decompose at high temperature is difficult to solve. Based on the above research, it is necessary to provide a composite silicon anode material capable of comprehensively improving the performance defect of the silicon material. Disclosure of Invention The invention aims to provide a composite silicon anode material, a preparation method thereof and a battery, wherein the composite silicon anode material coats a specific polymer to serve as an artificial SEI film, and all functional groups in the polymer act synergistically, so that the material structure is expansion-resistant, the interface is firm, the high-temperature stability and the ion transmission are high-efficiency, and the cycle performance, the multiplying power performance, the quick charge performance, the high-temperature performance and other performances of the battery are effectively improved. In order to achieve the aim of the invention, the invention adopts the following technical scheme: In a first aspect, the invention provides a composite silicon anode material, which comprises a silicon carbon material and an artificial SEI film coated on the surface of the silicon carbon material, wherein the artificial SEI film comprises a polymer, and the structural formula of a monomer of the polymer is as follows: ; Wherein R 1 contains alkenyl, and R 2 contains phenyl substituted by nitro. According to the invention, a specific polymer is coated to serve as an artificial SEI film, the synergistic effect among various functional groups in the polymer is achieved, the performance defect of a silicon-based material is comprehensively improved, wherein triazole rings in the polymer serve as a molecular chain core skeleton, a reduction product of a nitrogen-rich structure can enable the artificial SEI film to be more uniform and compact, the interfacial stability of a composite silicon negative electrode material is improved, active lithium loss is reduced, meanwhile, the chemical stability of the polymer is enhanced, nitro-substituted phenyl in the polymer has strong electron-withdrawing capacity and excellent chemical stability and thermal stability, oxidation resistance of the composite silicon negative electrode material can be effectively improved, the material is prevented from being oxidized and decomposed, stable structure and performance are still kept at a higher temperature, sulfur atoms of thiol groups in the polymer can form chemical bonds with active sites of the silicon surface, the interfacial binding force of the silicon-carbon material and the artificial SEI film is remarkably enhanced, the falling-off of the artificial SEI film is effectively prevented, in addition, allyl in a monomer of the polymer can be polymerized, a porous network can be formed after crosslinking, channels are provided for lithium ion transmission, the quick charge and performance of a battery can be improved, the volume expansion of the silicon particles can be buffered, the thermal expansion stress of the silicon negative electrode material can be kept, the stable structure can be stable at a higher temperature, the stable structure and stable performance can be stably achieved, the performance of the current structure can be stably and stable, the performance can be stably circulated, and stable performance can be stably have mult