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CN-122025556-A - Preparation method of negative electrode plate

CN122025556ACN 122025556 ACN122025556 ACN 122025556ACN-122025556-A

Abstract

The invention provides a preparation method of a negative electrode plate, which comprises the following steps of S1, mixing a silicon-carbon active substance, a conductive agent and a binder according to a mass fraction ratio of 8:1:1, simultaneously adding a solvent and a surface tension leveling agent to obtain slurry, S2, coating the slurry on a current collector to form the negative electrode plate, wherein the silicon-carbon active substance comprises a silicon-carbon inner core, silver particles attached to the inner core, and a carbon coating layer outside the inner core and the silver particles, and the carbon coating layer is hard carbon, and the surface tension leveling agent is at least two of isopropanol, ethylene carbonate and fatty alcohol polyoxyethylene ether. The electrode pole piece prepared by the invention improves the pole piece performance synergistically through silver deposition, hard carbon coating and adding the leveling agent for mirroring, and obviously improves the electronic conduction, ion transmission efficiency and interface stability of the pole piece.

Inventors

  • ZHOU WEI
  • FU WENWEN
  • LIU XUN
  • WU SHUANG
  • GAO JUNQIANG
  • TANG XIAOWEI
  • HUANG XIAOWEI

Assignees

  • 江西赣锋锂电科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260130

Claims (7)

  1. 1. The preparation method of the negative electrode plate comprises the following steps: S1, mixing a silicon-carbon active substance, a conductive agent and a binder according to a mass fraction ratio of 8:1:1, and simultaneously adding a solvent and a surface tension leveling agent to obtain slurry; and S2, coating the slurry on a current collector to form a negative electrode plate, wherein the silicon-carbon active substance comprises a silicon-carbon inner core, silver particles attached to the inner core, and a carbon coating layer outside the inner core and the silver particles, wherein the carbon coating layer is hard carbon, and the surface tension leveling agent is at least two of isopropanol, ethylene carbonate and fatty alcohol polyoxyethylene ether.
  2. 2. The preparation method of the negative electrode plate according to claim 1, wherein the silicon-carbon active material is prepared by the following steps of S1, adding a silicon-carbon material into a silver nitrate solution and a hydrofluoric acid solution, stirring in a planetary manner, filtering for 3-5 times, S2, drying in a vacuum environment at 60 ℃ for 12 hours to obtain a dried composite material, S3, mixing the dried composite material in the step 2 with a resin material according to a mass ratio of 10-15:0.5-2, adding the mixture into absolute ethyl alcohol, stirring for 2 hours at 60 ℃ until all the absolute ethyl alcohol is completely volatilized, and performing high-temperature carbonization treatment at 800-1000 ℃ to obtain modified silicon-carbon negative electrode particles.
  3. 3. The method for preparing a negative electrode sheet according to claim 2, wherein the resin material is one or more of phenolic resin, furfuryl alcohol resin, epoxy resin, and phthalonitrile resin.
  4. 4. The method for preparing the negative electrode plate according to claim 3, wherein the added surface tension leveling agent comprises 1-2% of isopropanol, ethylene carbonate and fatty alcohol polyoxyethylene ether by mass percent in the slurry.
  5. 5. The method of producing a negative electrode sheet according to claim 2, wherein the concentration of silver nitrate is 3 to 5 millimoles per liter.
  6. 6. The method of manufacturing a negative electrode sheet according to claim 2, wherein the hard carbon layer in the silicon carbon active material has a thickness of 5 to 20 nm a.
  7. 7. The method for producing a negative electrode sheet according to claim 6, wherein the mass fraction of silver content in the silicon-carbon active material is 1.5% to 2.1%.

Description

Preparation method of negative electrode plate Technical Field The application relates to the technical field of lithium ion batteries, in particular to a preparation method of a negative electrode plate. Background As lithium ion batteries proliferate in demand, industry demands for energy density are becoming more stringent. The theoretical specific capacity of the traditional graphite cathode is 372 mAh/g, which is difficult to succeed, and silicon is regarded as 'holy cup' of the next-generation cathode by virtue of the advantages of ultra-high capacity of 4200 mAh/g (11 times of graphite), low discharge platform of about 0.5V, second abundance of crust, environmental friendliness and the like. However, silicon expands by over 300% in volume during charge and discharge, electrode pulverization and falling off cause capacity cliff-like attenuation, and simultaneously, the low conductivity caused by the semiconductor nature enables snow with high rate performance to be frosted. How to simultaneously discipline two major diseases of 'expansion' and 'conduction' becomes the key of the high-energy-density battery periphery. Another path for improving the energy density is to improve the active material loading, but the thick coating process is very easy to cause the pole piece to be dried, warped, cracked and reduced in adhesive force, the assembly difficulty of the rear section is increased sharply, and the probability of low capacity and short circuit is increased. Therefore, there is a need to develop a battery negative electrode sheet that can enhance the peel strength of the electrode sheet, enhance the energy density and conductivity, and suppress the volume expansion during the charge and discharge process. Disclosure of Invention The invention provides a preparation method of a battery negative electrode plate, which aims to solve the defects in the preparation process of the negative electrode plate in the prior art, and comprises the following steps: The method comprises the following steps of S1, mixing a silicon-carbon active substance, a conductive agent and a binder according to a mass fraction ratio of 8:1:1, adding a solvent and a surface tension leveling agent to obtain slurry, S2, coating the slurry on a current collector to form a negative pole piece, wherein the silicon-carbon active substance comprises a silicon-carbon inner core, silver particles attached to the inner core, and a carbon coating layer outside the inner core and the silver particles, the carbon coating layer is hard carbon, and the surface tension leveling agent is at least two of isopropanol, ethylene carbonate and fatty alcohol polyoxyethylene ether. The preparation method of the silicon-carbon active material comprises the following steps of S1, adding a silicon-carbon material into a silver nitrate solution and a hydrofluoric acid solution, stirring in a planetary manner, filtering for 3-5 times, S2, drying in a vacuum environment at 60 ℃ for 12 hours to obtain a dried composite material, S3, mixing the dried composite material obtained in the step 2 with a resin material according to a mass ratio of 10-15:0.5-2, adding the mixture into absolute ethyl alcohol, stirring for 2 hours at 60 ℃ until all the absolute ethyl alcohol is completely volatilized, and performing high-temperature carbonization treatment at 800-1000 ℃ on the obtained material to obtain modified silicon-carbon anode particles. Further, the resin material is one or more of phenolic resin, furfuryl alcohol resin, epoxy resin and phthalonitrile resin. Further, the added isopropyl alcohol, ethylene carbonate and fatty alcohol polyoxyethylene ether in the surface tension leveling agent account for 1-2% of the mass fraction of the slurry. Further, the concentration of silver nitrate is 3-5 millimoles per liter. Further, the thickness of the hard carbon layer in the silicon carbon active material is 5-20 nm. Further, the mass fraction of silver content in the silicon carbon active material is 1.5% -2.1%. According to the preparation method of the negative electrode plate, silver particles are covered outside the silicon-carbon material, and the modified silicon-carbon material coated by hard carbon and the flatting agent are used together, so that the electronic conduction, ion transmission and interface stability of the battery plate are greatly improved, the processing defects are improved, and the initial effect and the cycle life of the battery are further improved. Drawings FIG. 1 is an SEM image of particles of a silicon-carbon material prepared according to example 1 of the invention; FIG. 2 is a graph showing the comparison of physicochemical properties of silicon-carbon materials prepared in various embodiments of the present invention; FIG. 3 is a comparative plot of the electrical properties of a negative electrode tab prepared in accordance with various embodiments of the present invention; FIG. 4 is a graph comparing peel strength of negative e