Improvement of usable capacity and cyclability of silicon-based anode materials for lithium batteries by sol-gel graphite matrix

High capacity silicon-graphite composite anode materials were made by dispersing silicon in a sol-gel graphite (SGG) matrix. The capacity increased with increasing Si content and the best application performance was delivered by a composite containing 19.2 wt % Si, where the first cycle discharge and charge capacities were 1033.7 mAh g(-1) composite (or 4311 mAh g(-1) Si) and 832.2 mAh g(-1) composite (or 3474 mAh g(-1) Si), respectively (80.5% coulombic efficiency). Capacity fading was less than 12% in 25 cycles, which is a substantial improvement over unsupported silicon anodes where precipitous drop in capacity occurs within a few cycles. The improvement is attributed to the presence of the SGG matrix, which, with its extensive open 3D network, effectively cushioned the volume change in the electrode during charging and discharging reactions, hence raising the usability in applications. (C) 2002 The Electrochemical Society.