Preparation And The Cycle Performance Of The Silicon Negative Electrode Material

Because of the increasingly serious energy crisis, it is necessary to findgreen environmentally-friendly energy to replace the traditional fossil energy.Non-pollution lithium ion battery is a new green energy. Larger capacity,longer life and higher safety for lithium ion battery are the research targets ofthe scientists worldwide.The silicone negative electrode materials have larger special capacity(theoretical special capacity is4200mA·h/g) and attract the attention of theresearchers in the whole world. But the volume change of silicon is largewhen the lithium-ion battery is charged and discharged. The structure ofsilicone negative electrode material is easily destroyed so that the electrode iseasy to be short circuit and the irreversible capacity of lithium-ion battery islarge. The silicon negative electrode materials were prepared and modified.Their properties were identified by XRD, SEM, and charging and dischargingtests. The silicon-copper negative electrode composite materials were preparedby chemical plating method. The effect of the copper content in thecomposite materials, temperature and pH in the solution were investigated.The results show that the first capacity of charge is2248mA·h/g,and thedischarge capacity is1231mA·h/g. The charging and discharging rate is55%at the first cycle. The capacity is still up to1018mA·h/g after42cycle times.As the volume expansion and stress of the material is relieved, the structureof silicone-copper composite material is stable in the electrochemical cycles.A complex coordination agent was used instead of the ordinary singlecoordination agent in chemical plating process and the capacity oflithium-ion battery increases.The silicon-copper negative electrode composite materials were sinteredin nitrogen at high temperature. The capacity of lithium-ion battery wasdetected. The results show that the best sintering temperature is1000℃when the capacity of the battery achieves416mA·h/g after30circle timesand the capacity has a rising tendency. The silicon and silicon-copper negative electrode composite materialswere composite by carbon-encapsulated processing. It shows that thecapacity of Si/C/Cu material can remain at864mA·h/g after30cycle times.Carbon and copper can ensure the battery cycle stability.