Silicon-carbon composite granules and preparation method and application therefor

Abstract

The invention discloses silicon-carbon composite granules and a preparation method and an application therefor. The silicon-carbon composite granules mainly comprise nanometer silicon, carbon nanotubes and organic cracked carbon; the carbon nanotubes wind mutually to form a porous granular structure; the carbon nanotubes alternately penetrate nanometer silicon gaps to form a porous structure to be used as a nanometer silicon carrier, and a conductive network is provided; by virtue of the porous structure, volume expansion of the nanometer silicon in a charging-discharging process can be effectively relieved; the space between the nanometer silicon and the carbon nanotubes is filled with the organic cracked carbon, so that attachment of the nanometer silicon on the carbon nanotubes can be improved, detachment of the nanometer silicon after volume deformation can be prevented, and direct contact between the nanometer silicon and an electrolyte is reduced at the same time; the silicon-carbon composite granules have excellent cycling performance, specific capacity, rate capability and low volume expansion effect, and can be used as an ideal negative electrode material of a lithium ion battery; and meanwhile, the production process is simple and easy to control, the product dimension is uniform, the appearance is regular and tidy, and large-scale industrial production can be achieved favorably.

Description

technical field [0001] The invention relates to a composite nanomaterial, in particular to a silicon-carbon composite particle and its preparation method and application, such as application in the field of lithium battery negative electrode materials. Background technique [0002] In the lithium-ion battery system, the negative electrode material of the battery is an important factor affecting the energy and cycle life of the lithium-ion secondary battery. The theoretical lithium storage specific capacity of silicon is 4200mAh / g, which is much larger than the theoretical capacity of graphite (372mAh / g), and it is the anode material with the highest theoretical capacity so far. [0003] However, the silicon electrode is often accompanied by a volume change of up to 300% during charge and discharge, resulting in the collapse of the electrode structure and the peeling off of the active material, resulting in a significant drop in electrode capacity or even complete failure, wh...

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Problems solved by technology

Among them, graphite, as the main material, can play the role of supporting nano-silicon and providing capacity. The coating of carbon nanotubes can provide a conductive network, but due to the high content of graphite, the specific capacity of the material is low, only about 500-600mAh/g , and the Coulombic efficiency is low

For another example, some researchers mixed organic carbon sources with nano-silicon and catalysts for growing carbon nanotubes and then sprayed and granulated to obtain precursors, and prepared silicon-carbon nanotube composite anode materials by vapor deposition of carbon sources, which have high specific capacity. , the first discharge reaches 2000mAh/g, and it reaches 1100mAh/g after 50 cycles, but the

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