Silicon-based negative electrode material, preparation method thereof and application of silicon-based negative electrode material in lithium-ion battery

Abstract

The invention relates to a silicon-based negative electrode material, a preparation method thereof and an application of the silicon-based negative electrode material in a lithium-ion battery. The silicon-based negative electrode material comprises a silicon-based active material and a composite layer, wherein the composite layer coats the surface of the silicon-based active material and is formedby a flexible polymer, flake graphite and a conductive material; and the method comprises the steps of (1) dissolving the flexible polymer into a solvent; (2) adding the flake graphite and the conductive material into a flexible polymer solution obtained in the step (1) under the stirring condition; (3) adding an anti-solvent to a mixed coating solution obtained in the step (2) and stirring; (4)adding the silicon-based active material to the supersaturated mixed coating solution obtained in step (3) under the stirring condition, stirring and separating; and (5) carrying out thermal treatmentto obtain the silicon-based negative electrode material. The silicon-based negative electrode material is simple in preparation method and low in cost, and industrial production is easy to implement;the prepared silicon-based negative electrode material has excellent electrochemical cycle performance and swelling inhibition performance, and the service life of the lithium-ion battery can be prolonged.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, and relates to a silicon-based negative electrode material, its preparation method and application, in particular to a silicon-based negative electrode material, its preparation method and its application in lithium-ion batteries. Background technique [0002] With the development of lithium-ion batteries to large-scale applications, performance indicators such as energy density and power density of lithium-ion batteries need to be further improved. In terms of negative electrode materials, the traditional graphite carbon negative electrode materials have limited specific capacity (372mAh / g), which has been difficult to meet the needs of high energy density batteries, and negative electrode materials with high specific capacity have become the focus of current research. Silicon-based materials have attracted much attention because of their theoretical specific capacity up to 4200mAh / g. Howev...

AI Technical Summary

Problems solved by technology

The key point of the technology is to coat the conductive polymer (polythiophene, polyaniline, polypyrrole) on the silicon-based material by in-situ polymerization, and add sodium alginate to enhance the stability, and build a three-dimensional network structure to buffer the expansion of the silicon material. The conductivity of the conductive polymer coated by the method is low, and the conductivity is unstable, and it is easy to dedope and lose conductivity, resulting in a decrease in the cycle performance of the material, and the in-situ polymerization preparation process used is complicated.

CN 105186003 A discloses a method for preparing a high-capacity lithium-ion battery negative electrode material. Polymers, conductive agents and non-carbon negative electrode materials are dispersed in a suitable solvent to form a uniform emulsion, and then frozen or spray-dried to obtain Uniform black powder material is dried under vacuum to obtain a high-capacity negative electrode material coated with a conductive polymer. The polymer is used to improve the volume change of the non-carbon negative electrode during the cycle, but the material prepared by this method, the conductive agent is dispersed in the active around the material, the connection with the active material will be lost during cycling, and the polymer’s strength is low, which does not effectively improve the expansion of non-carbon anode materials

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