酸浸蚀Al-Si合金制备锂离子电池高性能多孔硅负极材料

本文首次提出利用酸浸蚀Si-Al（含Al 80%）合金粉末的方法制备多孔硅材料. 分析表明制得的多孔硅材料为晶体，并具有由纳米颗粒结集成的海绵状多孔结构，其粒径约20 μm，比表面102.7 m²·g^-1. 多孔硅电极按多孔硅:导电碳:粘结剂 = 1:1:1（by mass）涂成. 在添加15%氟化碳酸乙烯酯（FEC）的1 mol·L^-1 LiPF₆/EC + DMC（1:1，by volume）电解液，在100 mA·g^-1电流密度充放电，多孔硅电极的首次放电比容量2072 mAh·g^-1 Si. 经237次充放电循环后，其放电容量仍可保持在1431 mAh·g^-1 Si，显示了相当高的充放电稳定性. 这归因于其海绵状多孔结构有足够的微空间以承受充电过程中硅的急剧膨胀. 硅微粒的纳米尺寸有利于锂在Li-Si合金中的扩散. 纳米硅微粒可牢固地联成一整体，不易因膨胀、收缩而粉化断裂. 这种构筑多孔硅负极材料的新方法操作简便、成本低廉，有着很好的应用前景.

Preparation of High Performance Porous Silicon Powders by Etching Al-Si Alloy in Acid Solution for Lithium Ion Battery

Porous silicon powders prepared by etching Al-Si alloy using an acid solution was reported in the first time. The morphology and structure of as-obtained material were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) method. It was found that the spongy porous silicon powders presented well crystalline structure and consisted of nano-Si particles. The particle size of porous Si powders was about 20 μm, and the specific surface area was 102.7 m²·g^-1. The electrochemical properties of porous silicon powders were evaluated as an anode material for lithium ion batteries. The material proportion in the porous silicon electrode was porous Si:conducting C:binder = 1:1:1. It was measured that in 1 LiPF₆ mol·L^-1, EC:DMC = 1:1 + 15%(by mass)FEC electrolyte, the first discharge capacity of porous silicon electrode was 2072 mAh·g^-1 Si, and the capacity of 1431 mAh·g^-1 Si was kept after 237 cycles at the charge and discharge current densities of 100 mA·g^-1. Such high electrochemical performance of porous silicon electrode could be attributed to the spongy porous structure, which provided enough tiny space to buffer the huge volume variation of Si anode during charging/discharging process. The nano-size of Si particles was benefited to the diffusion process of lithium in Li-Si alloy, and the firm connection between Si nanoparticles could prevent the breakage of porous Si particles. This advanced method for producing high performance porous Si powders is simple and low cost, and has a bright prospect for the practical application