Preparation And Lithium Storage Performance Of 3D Porous Silicon Materials

Because of the increasingly serious energy crisis, it is necessary to find green 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 of the scientists worldwide.3D porous silicon is an attractive anode material for LIBs due to the higher theoretical capacity, low cost, and environmental benignity. However, they generally suffer from poor cycle behavior since a large volume change occurs during the charge/discharge process. In this thesis, we aimed to design an anode having excellent electrochemical properties. We use TiO₂ and Ag to modify the 3D porous silicon material to improve the initial coulombic efficiency, capacity and cycle stability. The electrochemical performance of the synthesised composite materials was investigated by cyclic voltammetry and galvanostatic charge-discharge technique, respectively. And we can get the following conclusions:1、We prepared 3D porous silicon by Metal-Assisted Chemical Etching method and etching Al–Si alloy powder, compare and analyze the electrochemical performance of two kinds of 3D porous silicon when they are as the anode. The results show that the preparation of 3D porous silicon by etching Al–Si alloy powder have a better performance; lithiation and delithiation specific capacity during the first cycle, 1910.8/2567.6 mAh/g, with the initial coulombic efficiency of 74%, reversible discharge capacity is 430 mAh/g after 50 cycles at a current density of 100 mA/g.2、3D porous silicon/TiO₂ composite materials were synthesized successfully by a facile Sol-gel method under different contents of TiO₂. On the electrochemical testing, The results show that TiO₂ have great influence on the electrochemical performance of the 3D porous silicon material. when preparation of isopropyl titanate is 3 ml The 3D porous silicon/TiO₂ composites have the best electrochemical performance; lithiation and delithiation specific capacity during the first cycle, 859.7/1181.6 mAh/g, with the initial coulombic efficiency of 72.8%, reversible discharge capacity is 684.4 mAh/g after 50 cycles at a current density of 100 mA/g.3、We prepared 3D porous silicon/Ag composite material by Metal-Assisted Chemical Etching method for lithium ion battery anode materials, The effect of the sliver content in the composite materials and temperature were investigated. The results show that the preparation of 3D porous silicon/Ag composite under the condition of 20℃ and silver nitrate concentration of 20 mmol/L have the best electrochemical performance; ithiation and delithiation specific capacity during the first cycle, 1677/1906 mAh/g, with the initial coulombic efficiency of 88%, reversible discharge capacity is 755.5 mAh/g after 50 cycles at a current density of 100 mA/g.