Hollow/porous structure silicon-based composite material and preparation method thereof

Abstract

The invention discloses a hollow / porous structure silicon-based composite material. The composite material comprises a hollow / porous structure, a silicon-carbon composite layer and a coating layer, the silicon-carbon composite layer is formed by evenly dispersing nano silicon or silica in a conductive carbon network, the conductive carbon network in the silicon-carbon composite layer is formed with binder through pyrolysis, the coating layer is a carbon coating layer, and at least one carbon coating layer is provided. The composite material provided by the invention is prepared through a method of evenly mixing the nano silicon / silica, the binder and salt, then, performing spray granulation, high temperature sintering, water desalination and coating treatment. The composite material provided by the invention is a lithium ion battery silicon-carbon cathode material with the advantages, such as high first effect, low expansion and long cycle; grain growth of the silicon material in a thermal treatment process is slowed, powdering of the material in a cycle process is avoided effectively, volume expansion effect of the silicon-based material is remitted, cycle performance is promoted,and conductivity and rate capability of the material are improved.

Description

technical field [0001] The invention relates to the technical field of new energy materials, in particular to a hollow / porous silicon-based composite material and a preparation method thereof. Background technique [0002] Secondary batteries have been widely used in portable electronic products, but with the miniaturization of portable electronic products and the increasing demand for secondary batteries in aviation, military and automotive industries, the capacity and energy density of batteries need to be greatly improved . At present, commercial anode materials are mainly graphite materials, but due to their low theoretical capacity (372mAh / g), they cannot meet the market demand. In recent years, people have focused on new high-capacity anode materials: lithium storage metals and their oxides (such as Sn, Si) and lithium transition metal phosphides. Among many new high-capacity negative electrode materials, Si has become one of the most potential alternative graphite m...

AI Technical Summary

Problems solved by technology

Because the porous structure of the material is obtained by the environmentally unfriendly method of magnesia thermal reduction and pickling, and the process of magnesia thermal reduction and pickling is difficult to control, many reaction by-products will remain, so that the negative electrode material exhibits low The first efficiency of

[0004] For this reason, it is necessary to develop a kind of hollow / porous structure silicon-based composite material that can be used in lithium-ion batteries, and has the advantages of high first effect, low expansion and long cycle, and its preparation method for lithium-ion battery silicon-carbon negative electrode materials Overcome the huge volume effect of Si-based materials in the charging and discharging process in the prior art, which is prone to cracking and pulverization, thus losing contact with the current collector, resulting in a sharp decline in cycle performance, and the large volume effect and poor conductivity of Si-based negative electrode active materials. Low efficiency leads to technical problems such as poor cycle performance and poor rate performance

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