A kind of high-capacity silicon carbon material and preparation method thereof

Abstract

The invention relates to a high-capacity silicon-carbon material and a preparation method thereof. The silicon-carbon material uses a silicon material as a core and a carbon layer doped with a conductive agent as a shell. The preparation method includes: S1, uniformly mixing the silicon source, the coating agent and the conductive agent to obtain a mixed material; S2, fusing the mixed material; S3, high-temperature coating treatment; S4, high-temperature carbonization treatment. The invention can make the silicon source, the coating agent and the conductive agent bond more uniformly and closely during the fusion process, the addition of the conductive agent can enhance the conductivity of the silicon-carbon material, and the fusion process can avoid the agglomeration of the conductive agent particles , to make it evenly dispersed, and at the same time, through the high-temperature dynamic coating on the surface, the coating agent of the outer layer of the silicon source can modify the surface of the exposed silicon source, and a relatively stable and smooth solid electrolyte interface film can be formed on the carbon surface , so the prepared silicon carbon material can have high capacity and efficiency, and a good coating layer can effectively relieve the volume expansion of the silicon carbon material and improve the cycle performance.

Description

technical field [0001] The invention relates to the technical field of lithium batteries, in particular to a high-capacity silicon-carbon material and a preparation method thereof. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, and less environmental pollution. They have become the focus of research all over the world, and have been widely used in computers, mobile phones, and other portable electronic devices. However, with the rapid development of electric vehicles and advanced electronic devices, higher requirements are placed on the energy density of lithium-ion batteries. How to increase the energy density of lithium-ion batteries lies in the improvement of electrode materials and performance. [0003] At present, the anode materials of commercial lithium-ion batteries are mainly graphite materials, due to their low theoretical specific capacity (only 372mAh / g), and poor rate performance. Therefore, sci...

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Problems solved by technology

In this patent document, silicon oxide (SiO) is used as a raw material to make materials. Although the cycle and conductivity characteristics are improved, the reversible capacity is around 650mAh / g, and the first-time efficiency is less than 70%.

Although the silicon oxide composite negative electrode material has improved the specific capacity (>1600mAh / g) and the first coulombic efficiency (>80%) of the SiO composite material to a certain extent, the silicon oxide composite material is based on the original SiO material. On the basis of component structure, artificially introduced nano-silicon material with relatively large volume expansion on the surface of SiO particles by physical combination, the crystal grains are large and difficult to control, and the dispersion is poor. The huge silicon material itself brings The volume expansion problem cannot be avoided without effective buffering, and the cycle performance is poor

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