Graphene/solid-state electrolyte composite coated silicon composite negative electrode and preparation method thereof

Abstract

The invention discloses a graphene / solid-state electrolyte coated silicon composite material and a preparation method thereof. The preparation method comprises the following steps: coating a silicon-based material with a layer of graphene through a chemical vapor deposition method, and accumulating concentrated ammonia water into an oxide through a precursor ester of an oxide for coating to obtainan oxide and graphene co-coated silicon negative electrode material; performing lithiation on the composite material with lithium hydroxide monohydrate to finally obtain the graphene / solid-state electrolyte coated silicon composite material. In the composite material, graphene directly grows on the surfaces of silicon particles, and the surface of graphene is coated with solid-state electrolyte,thereby forming double-layer coating. The graphene inside can increase the electronic conductivity of the silicon-based material, and relieve volume expansion of silicon. The coating solid-state electrolyte outside can improve the Coulomb efficiency and the magnification performance of the silicon-based negative electrode material, reduce the electrochemical reaction between the negative electrodematerial and electrolyte, increase the Coulomb efficiency of the silicon-based negative electrode and improve the high current charging and discharging performance of the material.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a method for coating graphene / solid electrolyte material on the surface of a silicon negative electrode. Background technique [0002] In recent years, with the rapid development of electric vehicles and mobile electronic equipment markets, it is imminent to study lithium-ion batteries with high energy density, high power density, and long life. Silicon-based materials have become the most promising anode materials for next-generation lithium-ion batteries to replace graphite due to their high theoretical capacity (4200mAh / g), low plateau voltage (0.2V vs. Li / Li+) and abundant resources. However, the commercialization of silicon-based materials also faces some urgent problems, such as short cycle life, low Coulombic efficiency, and poor rate performance. Generally, when the lithium-ion battery is cycled for the first time, the electrolyte and the silicon negative e...

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Problems solved by technology

This method only mechanically mixes the silicon-titanium alloy and graphene through a ball mill, and cannot form a complete coating.

And in the process of coating oxides, soluble salts or esters first generate hydroxides under the action of ammonia water and then calcine to obtain oxides; after dissolving soluble salts or esters in a mixed solution of water and alcohol, it is necessary to pass inert gas to remove dissolved oxygen and carbon dioxide, this process needs to last 1-10h / L, which takes a long time

Moreover, the oxide coated on the outermost layer still does not solve the problem of poor electrical conductivity of the coating layer, which reduces the rate performance of the material.

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