Electrodeposition and Electrochemical Property of Porous Li-Si Film Anodes for Lithium-Ion Batteries

Porous Li-Si thin films (LSFs) were prepared by a multi-step constant current electrodeposition onto Cu foil. The structure and morphology of the electrodeposited films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). As anodes for Li-ion batteries, Li-Si films give high cycling stability, adjustable Li-storage capacity and initial coulombic efficiency under different electrodeposition conditions. For instance, LSF^-3 was electrodeposited in an electrolyte of 0.5 mol·L^-1 SiCl₄+0.7 mol·L^-1 LiClO₄+propylene caronate (PC) under certain conditions (i₁=-3.82 mA·cm^-2, t₁=600 s; i₂=-1.27 mA·cm^-2, t₂=7200 s). LSF^-3 showed the first coulombic efficiency of 97.1% at a current density of 12.7 μA·cm^-2. After the two initial pre-cycles, it delivered gravimetric and geometric charge capacities of 1410 mAh·g^-1 and 240.6 μAh·cm^-2 at 25.5 μA·cm^-2. After 50 cycles, its charge capacity was 179.0 μAh·cm^-2 (1049 mAh·g^-1), retaining 74.4% of its initial capacity. The porous structure in LSFs can accommodate a part of the volume change during Li insertion/extraction and this favors the structural stability.