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CN-122025585-A - Polymer surface modified silicon-carbon composite material and preparation method thereof

CN122025585ACN 122025585 ACN122025585 ACN 122025585ACN-122025585-A

Abstract

The invention relates to the field of lithium batteries, in particular to a polymer surface modified silicon-carbon composite material and a preparation method thereof. The preparation method comprises the steps of S1, dispersing a silicon-carbon material in a polar solution to obtain a silicon-carbon suspension, S2, dispersing a polymer in the polar solution to obtain a polymer dispersion, S3, dropwise adding the silicon-carbon suspension obtained in the step S1 into the polymer dispersion obtained in the step S2, S4, evaporating a solvent in the solution obtained in the step S3 to obtain powder, and S5, carbonizing the powder obtained in the step S4 at 300-400 ℃ to obtain the silicon-carbon composite anode material with the modified polymer surface. The method can not only remarkably inhibit the volume expansion of silicon in the circulation process, but also enhance the stability of the electrode-electrolyte interface.

Inventors

  • YANG XIAOGUANG
  • FAN XIULIN
  • WANG HUAN
  • DONG SHIHUI
  • LI RUHONG

Assignees

  • 浙江新安化工集团股份有限公司

Dates

Publication Date
20260512
Application Date
20260209

Claims (10)

  1. 1. The preparation method of the polymer surface modified silicon-carbon composite material is characterized by comprising the following steps: step S1, dispersing a silicon-carbon material in a polar solution to obtain a silicon-carbon suspension; Step S2, dispersing a polymer in a polar solution to obtain a polymer dispersion; step S3, uniformly mixing the silicon-carbon suspension obtained in the step S1 with the polymer dispersion obtained in the step S2; step S4, evaporating the solvent in the solution obtained in the step S3 to obtain powder; And S5, carbonizing the powder obtained in the step S4 at 300-400 ℃ to obtain the polymer surface modified silicon-carbon composite anode material.
  2. 2. The method according to claim 1, wherein step S3 is to add the silicon-carbon suspension obtained in step S1 dropwise to the polymer dispersion obtained in step S2, and continuously stir the polymer dispersion; or the polymer dispersion liquid obtained in the step S2 is added into the silicon-carbon suspension liquid obtained in the step S1 dropwise, and the silicon-carbon suspension liquid is continuously stirred.
  3. 3. The method of claim 1, wherein the polymer is at least one of polyacrylonitrile, polyaniline, or polyimide; And/or the polar solution is at least one of N, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide or ethanol.
  4. 4. The method of claim 1, wherein the concentration of the silicon carbon suspension is 30 g/L to 100 g/L; and/or the polymer dispersion has a concentration of 12.5 g/L to 100 g/L.
  5. 5. The method according to claim 1, wherein the solvent is evaporated under the condition that the solution obtained in step S3 is stirred at a speed of 300 to 400 r/min at 70 to 90 ℃ to obtain a solution of 5 to 8 h; and/or the solvent in the step S3 is evaporated and then dried; Preferably, the drying condition is from 8 to 12 h at 60 to 80 ℃.
  6. 6. The method according to claim 1, wherein the carbonization treatment in step S5 is 8-12 h, and the heating rate is 3-5 ℃.
  7. 7. The method of claim 1, wherein the mass ratio of silicon carbon material to polymer is from 40:1 to 10:1.
  8. 8. A polymeric surface modified silicon carbon composite material prepared by the method of any one of claims 1 to 7.
  9. 9. The polymer surface modified silicon-carbon composite material is characterized by comprising a silicon-carbon material and a semi-carbonization/conjugation structure coating coated on the surface of the silicon-carbon material.
  10. 10. A negative electrode for a lithium ion battery, comprising the polymer surface modified silicon-carbon composite material of claim 8 or 9.

Description

Polymer surface modified silicon-carbon composite material and preparation method thereof Technical Field The invention relates to the field of lithium batteries, in particular to a polymer surface modified silicon-carbon composite material and a preparation method thereof. Background The novel silicon-carbon composite material is regarded as a key negative electrode material of a next-generation high-energy-density lithium battery because of extremely high theoretical specific capacity (4200 mAh/g). However, its industrial application is limited by two major core bottlenecks: firstly, the cycle stability is extremely poor. Silicon undergoes a volume expansion and contraction of more than 300% during delithiation, and this dramatic volume change causes the active particles to break up, pulverize, and separate from the current collector. Meanwhile, the continuously broken surface can continuously generate an unstable and excessively thick SEI film, so that electrolyte consumption is accelerated, internal resistance is increased rapidly, capacity is reduced rapidly, and the cycle life is far from commercial requirements. Secondly, the quick-charging performance is poor. The large volume effect and interfacial instability exacerbate the risk of structural failure of the electrode under high rate charging. More importantly, the lithium ion diffusion rate of silicon is far lower than that of graphite, and the high current polarizes the electrode potential, so that the precipitation of lithium metal is easy to occur, and serious potential safety hazards are brought. Together, these factors lead to the difficulty in supporting rapid charging of the silicon-carbon negative electrode, and limit the exertion of the silicon-carbon negative electrode in high-frequency application scenes such as power batteries. Disclosure of Invention In order to solve the technical problems, the invention provides a preparation method of a polymer surface modified silicon-carbon composite material, which comprises the following steps: step S1, dispersing a silicon-carbon material in a polar solution to obtain a silicon-carbon suspension; Step S2, dispersing a polymer in a polar solution to obtain a polymer dispersion; step S3, uniformly mixing the silicon-carbon suspension obtained in the step S1 with the polymer dispersion obtained in the step S2; step S4, evaporating the solvent in the solution obtained in the step S3 to obtain powder; And S5, carbonizing the powder obtained in the step S4 at 300-400 ℃ to obtain the polymer surface modified silicon-carbon composite anode material. In some embodiments, the step S3 is to dropwise add the silicon-carbon suspension obtained in the step S1 to the polymer dispersion obtained in the step S2, and continuously stir the polymer dispersion; or the polymer dispersion liquid obtained in the step S2 is added into the silicon-carbon suspension liquid obtained in the step S1 dropwise, and the silicon-carbon suspension liquid is continuously stirred. In some embodiments, the polymer is at least one of polyacrylonitrile, polyaniline, or polyimide; in some embodiments, the polar solution is at least one of N, N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, or ethanol; in some embodiments, and/or the concentration of the silicon carbon suspension is from 30 g/L to 100 g/L; in some embodiments, the polymer dispersion has a concentration of 12.5 g/L to 100 g/L. In some embodiments, the solvent evaporates under conditions such that the solution obtained in step S3 is stirred at a rate of 300-400r/min at 70-90 ℃ for 5-8 h; In some embodiments, the solvent in step S3 is evaporated and then dried; In some embodiments, the drying conditions are from 8 to 12h at 60 to 80 ℃. In some embodiments, the mass ratio of the silicon carbon material to the polymer is 40:1 to 10:1. In some embodiments, the carbonization treatment in step S5 is 8-12 h, and the temperature rise rate is 3-5 ℃ per minute. On the other hand, the invention also provides a polymer surface modified silicon-carbon composite material, which is prepared by any one of the preparation methods. In still another aspect, a polymeric surface modified silicon-carbon composite is provided comprising a silicon-carbon material and a semi-carbonized/conjugated structure coating coated on the surface of the silicon-carbon material. In yet another aspect, a lithium ion battery anode is provided, comprising the polymer surface modified silicon carbon composite material described above. In some embodiments, the 60 cycle capacity retention of the lithium ion battery is greater than 49%. The core-shell structure has the beneficial effects that a polymer-based coating layer is constructed on the surface of the silicon-carbon particles and is converted into a stable conductive phase through heat treatment, so that the core-shell structure is successfully constructed. The conductive coating has the dual functions of the buffer layer and the conductive net