A kind of silicon carbon composite material and preparation method thereof, lithium ion battery

Abstract

The invention discloses a silicon carbon composite material, a preparation method thereof as well as a lithium ion battery. The silicon carbon composite material is structurally formed by coating a porous carbon layer on amorphous porous silicon; the hole wall of the amorphous porous silicon is in an amorphous state; and the specific surface area of the silicon carbon composite material is 10 to 200m<2> / g. When the silicon carbon composite material is applicable to the lithium ion battery, in a lithium intercalating process, the amorphous porous silicon isotropically expands, and the problems of pulverization and dropping off of amorphous porous silicon particles from an electrode caused by volumetric change can be solved. The hole wall of the amorphous porous silicon is at the amorphous state, so that a porous structure can be prevented from collapsing, the volumetric change in the lithium intercalating process can be reduced, and the lithium de-intercalating cycle life of the amorphous porous silicon is effectively prolonged. The specific surface area of the amorphous porous silicon of the silicon carbon composite material is large, a contact surface between the silicon carbon composite material which serves as the anode material and an electrolyte solution is increased, and lithium ions can be quickly exchanged on the contact surface.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a silicon-carbon composite material, a preparation method thereof, and a lithium ion battery. 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 accompanied by serious volum...

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Problems solved by technology

[0004] The porous silicon reported in the above literature has excellent lithium intercalation performance, but the preparation process is very complicated, time-consuming and laborious, and it is difficult to produce on a large scale

In addition to this special synthesis method, porous silicon is often prepared by electrochemical etching (patent CN201110108203.9 discloses an electrochemical etching method) and metal-assisted chemical etching. The former requires a single crystal silicon wafer, and only A thin layer of porous silicon can be etched on the surface of a single crystal silicon wafer, but the cost of raw materials is high and the yield is low, so it is difficult to be practical; the latter can use crystalline silicon powder to obtain more porous silicon, but these two methods The prepared porous silicon is all crystalline, because the crystalline porous silicon expands anisotropically during the lithium intercalation process, which easily leads to the collapse of the pore structure, thus the specific capacity decays faster, and the lithium intercalation cycle performance is poor.

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