Method for preparing silicon negative electrode material containing surface modification film

Abstract

The invention provides a method for preparing a silicon negative electrode material containing a surface modification film and belongs to the technical field of lithium ion batteries. The method comprises a step of dissolving a polymer into water, adding a silicon material, stirring while heating, and removing moisture in a solution to obtaining a silicon material coated with a polymer film A, anda step of dissolving PAN in an NMP solvent, stirring to completely dissolving the PAN, adding the silicon material coated with the polymer film A and a conductive agent into a PAN solution, stirringwhile heating, and removing the NMP solvent in the solution to obtain a silicon negative electrode material containing the surface modification film. A silicon negative electrode artificial modified film of the invention can satisfy the use of a common SBR type binder in a silicon carbon negative electrode, so that graphite and the silicon negative electrode respectively form suitable SEI films without mutual influence, and the cycle stability of a battery is further improved. The method for preparing the silicon negative electrode artificial modified film in the invention is simple and convenient, and the silicon carbon negative electrode can be compounded by using a conventional water-based compounding method.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing a silicon negative electrode material containing a surface modification film. Background technique [0002] Due to the advantages of high energy density, long cycle life and environmental friendliness of lithium-ion batteries, they are widely used in portable electronic products such as mobile phones and notebook computers and new energy vehicles. The density has reached the bottleneck, and the energy density is difficult to break through. [0003] In order to obtain lithium-ion batteries with higher energy density, nano-silicon, silicon oxide and silicon carbon have entered the world of lithium-ion batteries. However, the problems of swelling and pulverization of silicon negative electrodes and poor cycle performance cannot be fundamentally solved. Therefore, Nano-silicon, silicon carbon or a mixture of silicon oxide and graphite...

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Problems solved by technology

[0005] The purpose of the present invention is to provide a method for preparing a silicon negative electrode material containing a surface modification film in order to solve the problem of unstable cycle performance of the high specific energy silicon-carbon negative electrode and the inapplicability of the binder. The silicon negative electrode material prepared by the present invention is Used in conjunction with graphite, they are used together as negative electrode active materials to make silicon-carbon negative deposits. The polymer forms a modified film on the surface of silicon-carbon negative deposits, which can improve the energy density and cycle performance of lithium-ion batteries using the silicon-carbon negative electrodes.

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