High-performance lithium ion battery silicon-carbon cathode material and preparation method thereof

Abstract

The invention relates to a lithium ion battery high specific capacity silicon-carbon composite cathode material. The high-performance lithium ion battery silicon-carbon cathode material comprises a Si-SiOx / C / DC composite system with a specific surface area of 1-30 square meters per gram, wherein the composite system comprises C matrix, Si-SiOx compound stuck in the C matrix, carbon nanotube distributed in C matrix and Si-SiOx-C, and an organic pyrolytic carbon coating on the outermost layer. The high-performance lithium ion battery cathode material has high quality specific capacity, good cycle stability and long service life, and can be used as high energy density cell cathode material for portable mobile terminals and digital products.

Description

technical field [0001] The invention belongs to the field of materials science, and in particular relates to a silicon-carbon composite negative electrode material with high specific capacity for a lithium ion battery. Background technique [0002] Since the practical use of lithium-ion batteries in the 1990s, due to their outstanding advantages such as high voltage, high energy density, good cycle performance, small self-discharge, and no memory effect, they have been widely used in mobile terminals, digital products and portable mobile phones. Equipment, electric vehicles and energy storage power stations and other fields. However, with the birth of smart mobile terminal electronic equipment, it is difficult for lithium-ion batteries to meet their long-term use requirements. Due to the limited size of mobile terminals, the development of high-energy battery products is imminent. [0003] Most of the currently commercialized lithium batteries use lithium cobalt oxide / graph...

AI Technical Summary

Problems solved by technology

However, elemental silicon has the following problems as the negative electrode active material of the battery: (1) During the lithium intercalation process, Li 22 Si 5 Alloy phase, the volume change of the material reaches more than 300%

The mechanical internal stress generated by such a huge volume effect will gradually peel off the electrode active material from the current collector, and the silicon active phase itself will also be pulverized, thereby losing electrical contact with the current collector, resulting in a rapid decline in battery cycle performance; (2 ) low conductivity

Silicon itself is a semiconductor material with a low conductivity of only 6.7×10 -4 S cm-1, a conductive agent needs to be added to improve the electronic conductivity of the silicon active material; (3) it is difficult to form a stable SEI film

During the charge and discharge process, the huge volume effect will lead to the continuous exposure of silicon to the electrolyte, making it difficult to form a stable SEI film, resulting in a rapid decline in the cycle performance of electroactive materials

[0004] In many patent applications for Si-C composite negative electrode materials, the lithium storage capacity of the negative electrode material is improved by methods such as mixing, coating, and doping of silicon and graphite, but the dispersion of nano-scale silicon powder has not been completely solved. Solved, resulting in deactivation of some areas of the electrode

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