CN-121983566-A - Porous nano silicon-carbon composite anode material, preparation method thereof, anode piece and solid-state battery

CN121983566ACN 121983566 ACN121983566 ACN 121983566ACN-121983566-A

Abstract

The invention provides a porous nano silicon-carbon composite anode material, a preparation method thereof, an anode piece and a solid-state battery. The method comprises the steps of mixing biomass carbon raw materials with an alkaline agent, heating the mixture under an inert atmosphere to obtain porous hard carbon, adding nano silicon powder, a silane coupling agent and graphene oxide into a mixed solvent, sequentially stirring, filtering and drying the mixture after ultrasonic dispersion to obtain a nano silicon powder compound, mixing the porous hard carbon, graphite, carbon nano tubes and the nano silicon powder compound, adding a dispersing agent and deionized water into the mixture, performing ball milling and mixing to obtain mixed slurry, coating the mixed slurry on a substrate, drying the mixture to obtain a formed blank, carrying out sectional heating sintering on the formed blank under the inert atmosphere, cooling, stripping the substrate, and crushing to obtain the porous nano silicon carbon composite anode material. The porous nano silicon-carbon composite anode material has the advantages of reduced volume expansion rate, high specific capacity, long cycle performance and good electrochemical interface conductivity.

Inventors

SUN HUAPENG
LI LINGHUA
XU JIANJUN
LI BENCHAO
CHEN XIANGRONG

Assignees

郴州新能源电池材料研究中心
郴州市尚亿新能源有限公司
郴江实验室

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (10)

1. The preparation method of the porous nano silicon-carbon composite anode material is characterized by comprising the following steps of: (1) Mixing biomass carbon raw materials with an alkaline agent, and performing heating treatment at 700-900 ℃ in an inert atmosphere to obtain porous hard carbon; (2) Adding nano silicon powder, a silane coupling agent and graphene oxide into a mixed solvent of deionized water and ethanol, and sequentially stirring, filtering and drying after ultrasonic dispersion to obtain a nano silicon powder compound; (3) Mixing the porous hard carbon, graphite and carbon nano tube obtained in the step (1) with the nano silicon powder compound obtained in the step (2), adding a dispersing agent and deionized water into the mixture, and performing ball milling and mixing to obtain mixed slurry; (4) Coating the mixed slurry on a substrate, and drying to obtain a molded blank; (5) Carrying out sectional heating sintering on the molded blank body in inert atmosphere, cooling, stripping the substrate, and crushing the rest molded blank body to obtain the porous nano silicon-carbon composite anode material, wherein: the biomass carbon raw material is one or more of lignin, chitosan and straw; The alkaline agent is one or more of sodium hydroxide and potassium hydroxide; the silane coupling agent is one or more of gamma-aminopropyl triethoxysilane and gamma-glycidol ether oxypropyl trimethoxysilane; the dispersing agent is one or more of sodium carboxymethyl cellulose and polyethylene glycol; In the step (2), based on 100% of the total weight of the nano silicon powder, the silane coupling agent and the graphene oxide, the nano silicon powder accounts for 80-98% by weight, the silane coupling agent accounts for 1-15% by weight, and the graphene oxide accounts for 0.5-8% by weight; In the step (3), based on 100% of the total weight of the porous hard carbon, graphite, carbon nanotubes, nano silicon powder composite and dispersing agent, the porous hard carbon accounts for 15-40% by weight, the graphite accounts for 20-50% by weight, the carbon nanotubes accounts for 3-12% by weight, the nano silicon powder composite accounts for 15-40% by weight, and the dispersing agent accounts for 1-3% by weight.
2. The preparation method of the porous nano silicon-carbon composite anode material according to claim 1, which is characterized in that, In step (1), the weight ratio of biomass carbon raw material to alkaline agent is in the range of 1:1.2-1:3, or In step (1), biomass carbon feedstock is mixed with an alkaline agent and heated at 700-900 ℃ for 2-4 hours under an inert atmosphere.
3. The method for preparing a porous nano-silicon-carbon composite anode material according to claim 1, wherein in the step (2), the volume ratio of deionized water to ethanol in the mixed solvent of deionized water and ethanol is 1:1-1:3.
4. The method for preparing the porous nano silicon-carbon composite anode material according to claim 1, wherein the average particle size of the nano silicon powder is 20-80 nm, and the specific surface area is 50-300 m 2 /g.
5. The preparation method of the porous nano silicon-carbon composite anode material according to claim 1, which is characterized in that, The porous hard carbon has a porosity of 40-60% and a pore size distribution of 5-40 nm, or The porosity of the porous nano silicon carbon composite anode material is 30-50%, and the average pore diameter is 10-25 nm.
6. The method for producing a porous nano-silicon-carbon composite negative electrode material according to claim 1, wherein in step (3), the porous hard carbon is 20 to 38 wt%, the graphite is 25 to 40 wt%, the carbon nanotube is 5 to 8 wt%, the nano-silicon powder composite is 20 to 28 wt%, and the dispersant is 1 to 2 wt%, based on 100% of the total weight of the porous hard carbon, the graphite, the carbon nanotube, the nano-silicon powder composite, and the dispersant.
7. The method for preparing the porous nano-silicon-carbon composite anode material according to claim 1, wherein the step (5) of sectional heating sintering comprises heating to 300-400 ℃ at 5-10 ℃ per min, preserving heat to 1-2 h, heating to 700-900 ℃ at 3-5 ℃ per min, and preserving heat to 2-4 h.
8. A porous nano-silicon-carbon composite anode material, characterized in that it is prepared according to the method of any one of claims 1-7.
9. A negative electrode tab comprising the porous nano silicon carbon composite negative electrode material of claim 8.
10. A solid-state battery characterized in that the solid-state battery comprises a positive electrode tab, a solid-state electrolyte layer, and a negative electrode tab according to claim 9.

Description

Porous nano silicon-carbon composite anode material, preparation method thereof, anode piece and solid-state battery Technical Field The invention belongs to the technical field of solid-state batteries, and particularly relates to a porous nano silicon-carbon composite negative electrode material, a preparation method thereof, a negative electrode plate and a solid-state battery. Background With the rapid development of new energy automobiles, portable electronic devices and large-scale energy storage fields, the market has put forward severe demands on the energy density, the cycle stability and the safety performance of batteries. The all-solid-state battery uses the solid electrolyte to replace the traditional liquid electrolyte, so that the problems of easy liquid leakage and hidden danger of combustion and explosion of the liquid battery are solved radically, the all-solid-state battery has a wider electrochemical window, can be matched with positive and negative electrode materials with high specific capacity, becomes the core development direction of the next generation power battery and the energy storage battery, and the performance breakthrough of the all-solid-state battery also becomes the research focus of the new energy field. The cathode material is used as a core component of the all-solid-state battery, directly determines the energy density, the cycle life and the multiplying power performance of the battery, and is a key break for the technical upgrading of the solid-state battery. At present, a graphite negative electrode widely used by a commercial battery has a theoretical specific capacity of 372 mAh/g, and is difficult to meet the development requirement of a high-energy-density solid-state battery, and the development of a novel negative electrode material with high specific capacity becomes a research hot spot in the field. The silicon-based material has the ultrahigh theoretical specific capacity of 4200 mAh/g, so that the silicon-based material becomes the graphite substitute material with the highest potential, however, the silicon can generate volume expansion of up to 300% in the process of charging, discharging and lithium intercalation/deintercalation, electrode particles are easily pulverized, active substances are easily separated, interface contact failure between an electrode and a solid electrolyte can be caused, and meanwhile, the intrinsic electronic conductivity of the silicon is poor, so that the problems severely restrict the commercialized application of the silicon-based material in a solid battery. In order to solve the problem of volume expansion of the silicon-based negative electrode, various modification schemes are proposed in the prior art, including core-shell structure construction, doping modification, carbon material coating and the like. The technology is characterized in that a multilayer composite coating structure is constructed, the volume expansion of silicon is buffered by utilizing the mechanical constraint action of a carbon layer, or a fast ion conductor layer is introduced to optimize lithium ion transmission, but the structure generally has the problem of weaker interface binding force, the coating layer is easily stripped in the circulation process, the material performance is fast attenuated, and the technology can control the volume expansion to a certain extent and improve the circulation performance by doping and coating the carbon nano tube to construct a conductive buffer network, but the electrode-electrolyte interface characteristic of a solid battery is not optimized, the interface compatibility of a silicon-based material and a solid electrolyte is poor, the overall internal resistance of the battery is higher, and the multiplying power performance and the fast charging performance are limited. Besides silicon-based cathodes, other high-specific-capacity cathode materials such as alloys and the like are widely researched, and part of technologies are used for buffering volume expansion by constructing composite cathodes with pore structures, but the materials often have the problem of limited specific capacity improvement, and the preparation processes of directional pore channels, nano arrays and other structures are complex, so that raw materials and production cost are high, and large-scale industrialized application is difficult to realize. Meanwhile, the interface charge transfer resistance problem is another bottleneck that restricts the performance of all-solid-state batteries. Poor chemical compatibility, poor physical contact and overhigh grain boundary resistance between the electrode and the solid electrolyte can cause higher interfacial charge transfer impedance, seriously reduce the transmission efficiency of lithium ions and further influence the rate performance and the cycle stability of the battery. In the prior art, although the interfacial charge transfer impedance is tried to be reduced by means of surface po