Hollow silicon-carbon composite material for lithium-ion batteries, and preparation method thereof

Abstract

The invention relates to a hollow silicon-carbon composite material and a preparation method thereof. According to the hollow silicon-carbon composite material, the silicon-carbon composite material is spherical or ellipsoid secondary particles; the secondary particles have hollow structures, the shell is formed by compounding graphite sheets, a silicon material and amorphous carbon, the silicon material is uniformly adhered on the surface of the graphite sheet and between the graphite sheets, and the surfaces of all the graphite sheets and the silicon material are covered with an amorphous carbon protection layer; and the graphite sheets for forming the secondary particles are randomly oriented to each other. According to the present invention, the silicon-carbon composite material used as the lithium-ion battery negative electrode has electrochemical characteristics of high capacity, high Coulomb efficiency, low expansion and good cycle performance; the lithium-ion battery prepared from the silicon-carbon composite material has characteristics of high volume energy density, low expansion and good cycle performance; and the preparation process has advantages of simpleness, wide raw material source and low cost, and can achieve the industrial application of the silicon-carbon composite material in the lithium battery field.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a hollow silicon-carbon composite material and a preparation method thereof. Background technique [0002] Due to the rapid development and wide application of various portable electronic devices and electric vehicles, the demand for lithium-ion batteries with high energy density and long cycle life is increasingly urgent. At present, the negative electrode material of commercial lithium-ion batteries is mainly graphite, but due to the low theoretical capacity (372mAh / g), the further improvement of the energy density of lithium-ion batteries is limited. Among many new lithium-ion battery anode materials, silicon anode materials have the advantage of high capacity that cannot be matched by other anode materials (Li 22 Si 5 , with a theoretical lithium storage capacity of 4200mAh / g), which is more than 11 times the theoretical capacity of current commercial carbon anode mater...

AI Technical Summary

Problems solved by technology

However, due to the large specific surface area of ​​nano-sized silicon particles, the cycle efficiency of the battery is very low; and in the subsequent cycle process, the nano-silicon powder will reunite into large particles, resulting in a new volume effect

(2) Preparation of silicon materials with special nanostructures, such as silicon nanotubes, silicon nanowires, porous silicon, etc., but this method has high cost and low output, and is currently only suitable for laboratory research

When the material is prepared into a negative pole piece and then subjected to rolling treatment, the outermost amorphous carbon protective layer is easily crushed, causing the exposed silicon particles inside to be directly exposed to the electrolyte, resulting in a decrease in the cycle performance of the material

[0007] Therefore, the existing silicon negative electrode materials have poor electrochemical performance, complicated preparation process, and are difficult to realize practical application in lithium-ion batteries, which are technical problems in the field

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