A silicon-based composite negative electrode material and its preparation method and application

Abstract

The invention provides a method for preparing a silicon-based composite negative electrode material, comprising the following steps: (1) corroding silicon oxide particles to obtain silicon oxide with a porous structure; (2) in the presence of a catalyst, in the In-situ growth of carbon nanotubes on the surface and pores of silicon oxide with a porous structure; (3) carbon-coating the material obtained in step (2) by chemical vapor deposition to form a first coating layer; (4) The material obtained in step (3) is prepared into a mixed slurry with graphite, conductive agent, binder, and solvent, and the mixed slurry is spray-dried and granulated to form a second coating outside the first coating layer. cladding. The preparation method has simple process and low cost, and can be used in industrialized production; meanwhile, the obtained silicon-based composite negative electrode material has good conductivity and cycle stability. The invention also provides a silicon-based composite negative electrode material and its application.

Description

technical field [0001] The invention relates to the field of lithium ion battery materials, in particular to a silicon-based composite negative electrode material and a preparation method and application thereof. Background technique [0002] Due to the advantages of high energy density, long cycle life and environmental friendliness, lithium-ion batteries are widely used in portable electronic products such as mobile phones and notebook computers, new energy vehicles, and energy storage fields. The negative electrode material of the battery is graphite-based carbon material, but graphite-based carbon material has problems such as low theoretical capacity, poor compatibility with solvents, and poor high-rate discharge performance; therefore, it has the advantages of high capacity, high safety, and wide source of raw materials. Silicon-based materials used as negative electrode active materials have become an important research direction to improve the energy density of lithi...

AI Technical Summary

Problems solved by technology

[0002] Due to the advantages of high energy density, long cycle life, and environmental friendliness, lithium-ion batteries are widely used in portable electronic products such as mobile phones and notebook computers, new energy vehicles, and energy storage fields. The negative electrode material of the battery is graphite-based carbon material, but graphite-based carbon material has problems such as low theoretical capacity, poor compatibility with solvents, and poor high-rate discharge performance; therefore, it has the advantages of high capacity, high safety, and wide source of raw materials. Silicon-based materials used as negative electrode active materials have become an important research direction to improve the energy density of lithium-ion batteries.

[0003] However, the above-mentioned silicon-based negative electrode materials will have a large volume expansion during the charge and discharge process, which will cause problems such as powdering and falling off during the charge and discharge process, and the electrochemical connection between the active materials and the current collector will be lost; At the same time, it will also make the silicon-based negative electrode material unable to form a stable surface solid electrolyte film (ie SEI film) in the electrolyte. After the electrode structure is destroyed, the newly exposed silicon surface will form a new SEI film again, which will further lead to capacity fading, cycle reduction

In addition, the intrinsic conductivity of silicon is low, which restricts the migration rate of lithium ions, resulting in poor material rate performance.

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