SiOx@C-CNT-G composite negative electrode material, preparation method and lithium ion battery

Abstract

The invention provides a SiOx@C-CNT-G composite negative electrode material, which is provided with a plurality of secondary particles, the secondary particles comprise SiOx@C particles, carbon nanotubes and graphene sheets, the SiOx@C particles are SiOx particles coated with a nano carbon layer, and the carbon nanotubes grow in situ on the nano carbon layer of the SiOx@C particles; the graphene sheets are in bridge connection with the SiO@C particles through the carbon nanotubes; wherein the mass fraction of SiOx in the SiOx@C-CNT-G composite material is 60-90%. The graphene composite three-dimensional structure can provide space for volume expansion of SiOx particles, meanwhile, in-situ growth of CNT improves the conductivity and structural stability of the composite material, volume expansion of the material in the charging and discharging process is reduced, the contact surface of SiOx and an electrolyte is reduced through coating of graphene, and the stability of an SEI film of the composite material is improved.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a SiOx@C-CNT-G composite negative electrode material, a preparation method and a lithium ion battery. Background technique [0002] With the development of society, people's demand for energy is also increasing. The depletion of fossil energy and the serious environmental pollution caused by it make it urgent for human beings to find sustainable green energy. Lithium batteries have the advantages of high energy density, long cycle life, low maintenance cost, and environmental friendliness, which meet the application requirements of large-scale energy storage systems. [0003] At present, graphite, a commercial anode material, cannot meet the needs of large-scale energy storage systems due to its theoretical specific capacity of only 372mAh / g. With the development of lithium-ion battery negative electrode materials, it is found that silicon materials ar...

AI Technical Summary

Problems solved by technology

[0004] However, the electrical conductivity of silicon-based composite materials is low, and the expansion coefficient of silicon-based materials is high during charging and discharging. The secondary particle structure after carbon coating and granulation is not firm and easily destroyed, resulting in the disintegration of the composite material structure of composite carbon. The new silicon particle interface is exposed, the surface SEI grows, the cycle efficiency decreases, and the cycle performance decreases

[0005] At present, most of the research in this area is based on the simple compounding of graphene oxide and industrially prepared CNTs, but the preparation process is very complicated, and it is necessary to use additives to compound CNTs into materials through complex chemical reactions, which is difficult to produce on a large scale, and the secondary structure is also difficult. Unstable, easy to disintegrate during charging and discharging

As reported in CN109286012A, silicon ester and graphene oxide are used to react in a rotary evaporator, the operation is complicated, it is difficult to scale up mass production, and the prepared material has an unstable secondary structure and poor performance

There is also the use of metal catalysis to grow CNT on the surface of silicon-based materials, which will introduce metal impurities, which will cause battery self-discharge, decomposition of electrolyte, and lead to battery failure.

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