Composite silicon negative electrode material, and preparation method and application thereof

Abstract

The invention relates to a composite silicon negative electrode material. The composite silicon negative electrode material comprises nanometer silicon, a nanometer composite layer coating the surface of nanometer silicon and a conductive carbon layer uniformly coating the nanometer composite layer, wherein the nanometer composite layer is silicon oxide and metal alloy. According to the composite silicon negative electrode material with a three-layer structure, the nanometer composite layer composed of the silicon oxide and the metal alloy coating the surface of the silicon oxide effectively reduces volume expansion of the nanometer silicon, maintains the characteristic of high conductivity of the silicon material, improves mobility of lithium ions, prevents direct contact between a silicon negative electrode and an electrolyte, and can form a hard SEI film on the surface of the composite silicon negative electrode material, thereby allowing the cycle performance of the material to be substantially enhanced. The composite silicon negative electrode material has the characteristics of high capacity (greater than 1500 mAh / g), long cycle life (with a capacity retention ratio of more than 90% after 300 cycles) and high conductivity. The preparation method for the composite silicon negative electrode material is simple, easily controllable, and applicable to industrial production.

Description

technical field [0001] The present invention relates to a composite silicon negative electrode material, a preparation method thereof, and a lithium ion battery prepared using the negative electrode material, which belong to the field of lithium ion battery negative electrode materials and electrochemistry. Background technique [0002] As an energy storage device, lithium-ion batteries have the advantages of high energy density, small self-discharge, wide operating voltage range, no memory effect, long service life, and no environmental pollution. They have been widely used in 3C consumer electronics, energy storage, and new energy vehicles. and other fields. The key electrode material of lithium-ion battery is the final decisive factor of battery performance, and the negative electrode material plays a vital role in improving the performance of lithium-ion battery. At present, the application of negative electrode materials is mainly based on traditional graphite material...

AI Technical Summary

Problems solved by technology

[0006] CN101777651A discloses a lithium-ion battery negative electrode material, including active material silicon powder and volume buffer silica, wherein silicon is coated or partially coated on the surface of silicon dioxide particles. It is prepared by mixing silicon oxide with carbon reducing agent, and then sintering at high temperature in vacuum. However, it is difficult to prepare a dense active silicon layer through the reduction reaction of carbon and silicon dioxide in this method, and the thickness of the silicon layer is also difficult to control, resulting in the cycle of negative electrode materials. The performance will be significantly deteriorated and the capacity of the negative electrode material is also difficult to control

[0007] CN102709563A discloses a silicon negative electrode material for lithium-ion batteries. The negative electrode material includes nano-silicon powder and a silicon dioxide coating layer coated on the surface of nano-silicon. The patented silicon negative electrode disperses nano-silicon in sodium silicate solution, Then add graphite and inorganic acid to precipitate and coat copper foil, and dry it at 150°C. This method is difficult to ensure that the silicon dioxide is completely covered on the silicon surface, and the graphite conductive network is only mechanically mixed in the silicon negative electrode material. , so it is also difficult to suppress volume expansion during silicon cycling

[0008] The technical solutions disclosed in CN101777651A and CN102709563A are to coat silicon on the buffer surface or coat the buffer layer on the silicon surface. Although the volume expansion of part of the silicon can be suppressed, the electrical conductivity of the silicon itself has not been significantly improved, resulting in a long cycle life that cannot be guaranteed.

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