Method for preparing silicon-carbon composite material by molten salt electrolysis

Abstract

The invention discloses a method for preparing a silicon-carbon composite material through molten salt electrolysis. The method comprises the following steps: introducing CO2 gas in a CaCl2-CaSiO3-CaOmolten salt electrolysis process; dissolving CaSiO3 in molten salt to obtain silicate ions, and reducing the silicate ions at the cathode of an electrolytic tank to obtain a nano silicon material; capturing CO2 by utilizing oxygen ions in CaCl2-based molten salt, immobilizing the CO2 into carbonate ions, enabling the carbonate ions to reach a cathode through diffusion in the molten salt, and reducing the carbonate ions into a nano-carbon material on the cathode, thereby obtaining the silicon-carbon composite material on the cathode. The prepared silicon-carbon composite material utilizes thegood structural stability, flexibility and lubricity of the carbon material, so the silicon carbon composite material has the advantages of high specific capacity of silicon storage, high conductivityof a carbon material and the like, thereby solving the problems that the volume of silicon can be changed slightly in the silicon embedding process of lithium ions and the silicon is expanded and pulverized when lithium is embedded into silicon. Moreover, the obtained silicon carbon composite material has the advantages of high specific capacity of silicon storage, high conductivity of the carbonmaterial and the like and achieves the purpose of complementary advantages.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a method for preparing a silicon-based negative electrode material of a lithium ion battery. Background technique [0002] Lithium-ion batteries are commonly used energy storage and conversion devices in modern life. Today, the actual charge and discharge capacity of graphite has reached its theoretical limit. With the development of renewable energy and electric vehicles, the energy density of lithium-ion batteries is increasingly demanding. In order to improve the energy density of lithium-ion batteries, it is necessary to develop high-capacity and long-life anode materials, and the theoretical lithium storage specific capacity of silicon is 4200mAh / g. Among all the elements that can be alloyed to store lithium, the specific capacity of silicon is the highest. of. [0003] However, silicon itself has a fundamental defect that must be overcome, that is, when Li i...

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Problems solved by technology

[0004] In view of this, the purpose of the present invention is a method for preparing silicon-carbon composite materials by molten salt electrolysis, to solve the problem that silicon is used as the negative electrode material of lithium batteries, and when lithium is embedded in silicon, the silicon product will expand and pulverize. And improve the overall electrical conductivity of silicon-based materials

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