Silicon-carbon composite material, preparation method of silicon-carbon composite material, and lithium ion battery containing silicon-carbon composite material

Abstract

The invention discloses a silicon-carbon composite material, a preparation method of the silicon-carbon composite material, and a lithium ion battery containing the silicon-carbon composite material. The preparation method comprises the following steps of: (1) reducing silicon dioxide by using metal with activity larger than that of silicon, so as to obtain a porous silicon-metal oxide composite; (2) corroding the metal oxide by acid, so as to obtain porous silicon; and (3) coating the surface of the porous silicon by carbon by taking a carbon source as a raw material, so as to obtain the silicon-carbon composite material. The silicon in the silicon-carbon composite material is prepared through using a metallothermic reduction method and porous silicon particles prepared through using the metallothermic reduction method are micron-sized and hardly agglomerate; the pore walls and the pore diameters in the porous silicon particles are nano-sized; compared with imporous micron-sized silicon powder, for the silicon-carbon composite material, the porous silicon particles have the characteristics that a diffusion path of a lithium ion in a silicon substrate is shortened, thus being beneficial to charging and discharging with large current, the pores can hold the volume expansion of silicon during silicon intercalation and the charging and discharging cycle life of the material is prolonged. The surfaces of the porous silicon particles are coated with a carbon layer with the certain pores and the conductivity of the silicon-carbon composite material is enhanced.

Description

technical field [0001] The invention belongs to the technical field of battery manufacturing, and in particular relates to a silicon-carbon composite material, a preparation method thereof, and a lithium ion battery containing the material. Background technique [0002] At present, lithium-ion batteries used in production mainly use graphite-based negative electrode materials, but the theoretical lithium intercalation capacity of graphite is 372mAh / g, and the actual use has reached 370mAh / g. Therefore, graphite-based negative electrode materials have almost no improvement in lithium storage capacity. space. [0003] In the past ten years, a variety of new high-capacity and high-rate negative electrode materials have been developed, among which silicon-based materials have become a research hotspot due to their high mass specific capacity (the theoretical specific capacity of silicon is 4200mAh / g). During the lithium intercalation and desorption process, the material is acco...

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Problems solved by technology

[0004] The above method is very effective in overcoming the specific capacity fading problem of silicon-based negative electrode materials, but because the above method uses expensive raw materials (nano-silicon powder), it is difficult to produce on a large scale

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