CN-122000309-A - Silicon-carbon negative electrode material and preparation method thereof

CN122000309ACN 122000309 ACN122000309 ACN 122000309ACN-122000309-A

Abstract

The invention discloses a silicon-carbon negative electrode material, which comprises a porous petroleum-based carbon material, hard carbon distributed on the surface and in pores of the porous petroleum-based carbon material, and a nano silicon-based material and a carbon nano material embedded in the porous petroleum-based carbon material. The silicon-carbon negative electrode material takes a porous petroleum-based carbon material as a matrix, can inhibit the problems of pulverization of materials, electrode failure and the like in the charge-discharge process by embedding the nano silicon-based material and the carbon nano material into the porous petroleum-based carbon material, can effectively inhibit the contact between the silicon-based material and electrolyte by distributing a hard carbon layer in pores of the porous petroleum-based carbon material, prevents the repeated formation of an SEI film, enhances the conductivity of the silicon-based negative electrode, and effectively improves the cycle performance of the silicon-based material, thereby realizing the application of the silicon-carbon material in lithium ion batteries. The preparation method of the silicon-carbon anode material has the advantages of no pollution, simple operation, environment-friendly and easily available raw materials, low equipment cost and easy realization of continuous production.

Inventors

LIU YINDONG
DING YI
WANG LUHAI
LI YONGFENG
QI CHUANLEI
YANG WANG
CHEN ZHUO
LI SHENGPING
WANG JIARAN
CAO YUTING

Assignees

中国石油天然气股份有限公司
中国石油大学(北京)

Dates

Publication Date: 20260508
Application Date: 20241106

Claims (10)

1. The silicon-carbon negative electrode material is characterized by comprising a porous petroleum-based carbon material, hard carbon distributed on the surface and in pores of the porous petroleum-based carbon material, and a nano silicon-based material and a carbon nano material embedded in the porous petroleum-based carbon material; The mass of the silicon-carbon anode material is 100%, the content of the porous petroleum-based carbon material is 55% -90%, the content of the hard carbon is 3% -20%, the content of the nano silicon-based material is 4% -20%, and the content of the carbon nano material is 1% -5%.
2. The preparation method of the silicon-carbon anode material is characterized by comprising the following steps of: S1, mixing a micron-sized silicon-based material, a carbon nano material, an activator, a binder and a solvent until the binder is dissolved, and then sanding to obtain a first mixture; S2, carrying out ultrasonic mixing on the first mixture and petroleum coke materials to obtain a second mixture; s3, ball milling the second mixture to obtain a precursor of the silicon-carbon anode material, carbonizing, acid washing, drying, grinding and screening to obtain the silicon-carbon anode material; Wherein the mass ratio of the activator to the petroleum coke material is 1 (5-25); The Hard grindability index of the petroleum coke material is more than 70; the activator is selected from alkali metal salts of alkalinity; the carbon nanomaterial is at least one of graphite microchip, graphene, carbon nanotube and carbon fiber; the shape of the silicon-based material is at least one selected from sphere, spheroid, flake, linear and tubular; The mass of the micron-sized silicon-based material, the mass of the carbon nano material, the mass of the binder and the mass of the petroleum coke material are calculated as 100%, the mass of the micron-sized silicon-based material is 3% -19%, the mass of the carbon nano material is 0.5% -4.5%, the mass of the binder is 5% -22%, and the mass of the petroleum coke material is 56% -91%.
3. The method according to claim 2, wherein the silicon-based material is at least one selected from the group consisting of silicon particles and silicon oxides, and preferably the silicon-based material has a size of 1 to 20. Mu.m; In the silicon-based material, the diameter of the sphere is smaller than 5 mu m, the dimension of the quasi-sphere is smaller than 5 mu m, the thickness of the flake is smaller than 5 mu m, and the diameter of the tube is smaller than 5 mu m.
4. The method according to claim 2 or 3, wherein the carbon nanomaterial is 1-200nm in size, preferably the graphite micro-plate is less than 50nm in thickness and 0.2-1 μm in plate diameter, the graphene is less than 10nm in thickness and 0.2-1 μm in plate diameter, and the carbon nanotubes are 1-50nm in diameter.
5. A method of preparation according to claim 2 or 3, wherein the binder is selected from the group consisting of aqueous binders, preferably at least one of carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, chitosan, alginate; the solvent is selected from deionized water.
6. A method of preparation as claimed in claim 2 or 3 wherein the activator is selected from at least one of NaOH, KOH, na 2 CO 3 、NaHCO 3 、K 2 CO 3 、KHCO 3 .
7. The method of claim 2 or 3, wherein the mass to volume ratio of the binder to the solvent is (0.5-4) g/100 mL.
8. A method according to claim 2 or 3, wherein in step S1, the mixing is performed under stirring, and the stirring speed is 100-250r/min.
9. A method according to claim 2 or 3, wherein the carbonization is carried out at a temperature of 600-1500 ℃ for a time of 1-6 hours and a heating rate of 3-10 ℃ per minute.
10. The method of claim 2 or 3, wherein the ball milling time is 2 to 6 hours; the ultrasonic mixing time is 0.5-2h.

Description

Silicon-carbon negative electrode material and preparation method thereof Technical Field The invention relates to the field of lithium ion batteries, in particular to a silicon-carbon negative electrode material and a preparation method thereof. Background Lithium Ion Batteries (LIBs) have become the most important energy supply devices for supporting normal operation of portable devices such as mobile phones, notebooks, video cameras and the like, however, with the development of the age, new electrode materials with high rate performance are imperative. As for the negative electrode material, a silicon-based negative electrode material is considered as one of candidate materials most promising for application to next-generation high-energy-density lithium ion batteries due to its ultra-high theoretical specific capacity (4200 mA h g -1), which is 11 times that of the graphite-based carbon material (372 mAh g -1) currently commercialized on a large scale. However, the practical application of the Solid Electrolyte Interface (SEI) is difficult due to the limitation of the Solid Electrolyte Interface (SEI), such as serious volume expansion of silicon-based materials in lithium intercalation/deintercalation, thus the electrode is crushed, and the Solid Electrolyte Interface (SEI) is repeatedly grown, so that the conductivity is poor and the cycle performance is reduced. The problem of repeated growth of SEI can be solved by nanocrystallizing the silicon-based material, regulating and controlling the structure of the silicon-based material, preparing the silicon-based composite material and other methods to maintain the electrochemical performance of the silicon-based material. Aiming at the problem of serious volume expansion, the most direct method starts from the volume of silicon, and the particle size of silicon particles is reduced, so that the volume expansion of the silicon can be effectively relieved. Huang et al found that silicon nanoparticles had a very strongly particle-size-dependent fracture behavior during the first alloying process, i.e., particle diameter had a non-negligible effect on the cycling stability of nano-Si, through in situ transmission electron microscopy and the like. The study suggests that 150nm is a critical size for the breaking behaviour of silicon nanoparticles below which cracking of the particles does not occur, and above which cracking of the particles occurs. Therefore, the nanocrystallization of the Si material can be used as a basic means, and other modes are further introduced, so that the advantage of small volume expansion caused by nanocrystallization can be realized, and adverse effects caused by secondary agglomeration are eliminated. The composite material is a very good idea for improving the performance design of the silicon-based anode material, and the advantages of several materials can be concentrated into one composite material, so that the electrochemical performance of the material is greatly improved. Silicon provides high specific capacity, carbon has good conductivity and mechanical strength, wide sources and rich varieties, and the charging and discharging platforms of the silicon and the carbon are very low, belong to the same main group, have good compatibility and multiple synthesis methods, are economical and environment-friendly, and are considered as optimal candidates for realizing commercialization of high-energy-density lithium ion batteries in the industry. At present, carbon materials which are more studied and compounded with silicon mainly comprise graphite, graphene, carbon nano tubes, pyrolytic carbon and the like. Researchers design silicon-based materials into special structures, such as core-shell structures, porous structures and the like, so as to improve the lithium storage performance of the silicon-based materials. Wen et al designed a Si@C with a core-shell structure by coating a polymer film with resorcinol-formaldehyde resin coating from SiO 2 nanoparticles, calcining at high temperature to form a SiO 2 @C coated structure, and then removing part of the silica by hydrothermal method to form a so-called core-shell (egg yolk eggshell) structure. Finally, a magnesia reduction method is used for endowing the inner core with a porous structure, so that the performance of the material in circulation is further improved. Aiming at the problems of volume expansion and poor conductive ion conducting performance of silicon in the process of lithium intercalation and deintercalation, scientific researchers propose a plurality of solutions from different angles. The nano silicon materials with various structures are used for carrying out structure regulation and control on the silicon-based materials, and the electrochemical performance of the silicon materials is greatly improved by compounding the nano silicon materials with other materials. For example, a multi-layer coating structure silicon-carbon composite material and a prepar