Si/BiPO4 composite anode material for lithium ion batteries prepared by solvothermal method.

Lithium ion batteries play an important role in various energy storage technologies due to their good safety performance. As an anode material, silicon has attracted attention for its higher theoretical capacity than commercial graphite. But large volume expansion and unstable solid electrolyte interface (SEI) during the cycling of silicon lead to rapid capacity decay, which limits the commercial application of silicon anode. In this article, Si/BiPO 4 anode materials were prepared by solvothermal reaction. After morphology analysis and constant current charge discharge cycle analysis of Si/BiPO 4 anode materials with different mass ratios, it was found that Si/BiPO 4 anode materials with the mass ratio of 7:3 exhibited more excellent electrochemical performance. The conversion reaction of BiPO 4 and Li generates Bi and Li 3 PO 4 , and the alloying reaction of Bi generates Li 3 Bi. Bi and Li 3 Bi reduce the internal resistance of the Si/BiPO 4 composite, and Li 3 PO 4 is distributed on the surface of Si material, participating in the formation of SEI film and improving the stability of the material. At a current density of 500 mA g−1, the first discharge specific capacity of the Si/BiPO 4 anode is 2672.1 mA h g−1. After 200 cycles, the discharge specific capacity remains at 1308.9 mA h g−1. The electrochemical impedances of pure Si and Si/BiPO 4 anode materials before and after cycling were analyzed. It was found that the resistance of the Si/BiPO 4 anode before and after 100 cycles was lower than that of pure Si materials, which further proved that the addition of BiPO 4 material helps to improve the charge transfer ability of pure silicon materials. [ABSTRACT FROM AUTHOR]