Lithium ion battery composite negative material and preparation method thereof

Abstract

The invention discloses a lithium ion battery composite negative material. The lithium ion battery composite negative material is prepared from silicon oxide, as well as a soluble salt of refractory metal dissolved in a medium solution; the silicon oxide and the soluble salt are mixed, so that the surface of the silicon oxide is coated with the soluble salt of the refractory metal, and after the high-temperature heat treatment, a silicon-silicon alloy negative material coated with the silicon alloy is obtained, wherein a molar ratio of the silicon in the silicon oxide and the soluble salt of the refractory metal is 0.05 to 0.5; the silicon alloy coating on the surface of the silicon is performed by adopting in-situ chemical reaction, due to the good adhesion property, the synthesized silicon alloy coating can be effectively adhered onto the surface of the silicon material, so that the volume expansion of the silicon material in the charging and discharging process can be effectively alleviated; the conductivity of the silicon can be improved by virtue of the silicon alloy, the oxidation resistance of the negative material can be improved, and the high-temperature stability and chemical stability of the negative material can be improved; and the stability between the silicon and air or electrolyte liquid interface can be effectively improved, so that the electrochemical performance of the negative material can be greatly improved.

Description

technical field [0001] The invention relates to the technical field of lithium ion battery negative electrode materials, in particular to a lithium ion battery composite negative electrode material and a preparation method thereof. Background technique [0002] The rapid development of social economy and science and technology, on the one hand, has brought great convenience to people's life, on the other hand, it has also led to increasingly severe environmental and energy crises. With the depletion of traditional fossil fuels such as coal, oil, natural gas and other resources, the development of new energy is of great significance. In this context, chemical power sources, especially new chemical energy storage devices, are attracting more and more attention. As a conversion and storage device of electrical energy and chemical energy, lithium-ion batteries have the advantages of small size, light weight, high working voltage, high energy density, long cycle life, small self...

AI Technical Summary

Problems solved by technology

[0004] There are two key problems in the commercial application of silicon-based materials: First, silicon is an alloy-type lithium storage material. During the charging and discharging process, the crystal structure of silicon expands and contracts, causing a huge volume effect in the electrode material, resulting in electrode material powder. The active material loses effective electrical contact and shows poor cycle stability; secondly, the silicon material is in direct contact with the electrolyte and the SEI film at the interface is continuously broken and formed due to its serious volume change, and the continuous formation of SEI will Consumes electrolyte and lithium ions, reduces material conductivity, increases irreversible capacity loss and causes active material to fall from collector

However, nano-silicon materials are easily oxidized into silicon dioxide due to their large specific surface area and high surface activity. The oxidized nano-silicon materials show a low reversible specific capacity and even lose their electrochemical activity.

Images