Carbon-coated mesoporous silicon microsphere anodes with greatly reduced volume expansion

Carbon-coated nanostructured silicon (Si/C) composites are promising anodes for next-generation lithium-ion batteries, but scalable synthesis of such materials with an anti-pulverization capability, high areal capacity and long cycle life still remains a challenge. In this work, mesoporous Si/C microspheres of similar to 165 nm diameter are synthesized by magnesiothermic reduction of porous silica followed by chemical vapor deposition of a thin carbon layer. They consist of numerous primary Si nanocrystals of similar to 10 nm diameter which are interconnected, surrounded by abundant internal pores and coated with conductive graphitic carbon. These ameliorating structural and functional features offer a unique synergy that contributes to prevention of pulverization of Si/C microspheres with a highly reduced volume expansion of similar to 85% upon full lithiation. The Si/C electrodes deliver a reversible capacity of similar to 1500 mA h g(-1) at 0.1 A g(-1), an exceptional long-term stability of similar to 90% capacity retention even after 1000 and 2500 cycles at 1.0 and 4.0 A g(-1), respectively, and an excellent areal capacity of similar to 1.44 mA h cm(-2) after 500 cycles.