Fabrication of Porous Si@C Composites with Core-Shell Structure and Their Electrochemical Performance for Li-ion Batteries

Abstract

The pores in silicon particles can accommodate the volume expansion of silicon during the charging–discharging process. However, pores in silicon particles are easily occupied by carbon during the preparation of silicon/carbon composites. In this paper, sulfur was adsorbed in the pores of porous silicon particles before polyaniline (PANI) coating by in-situ polymerization, so that the pores were preserved in porous silicon@carbon (p-Si/@C) composites after the sublimation of sulfur during carbonization. The microstructure and the electrochemical performances of the obtained p-Si/@C composites were investigated. The results indicate that p-Si/@C composites prepared with a sulfur-melting process show a better high-rate performance than those without a sulfur-melting process. Remarkably, the former show a better capacity retention when returning to a low current density. The reversible capacities of the former were 1178 mAh·g−1, 1055 mAh·g−1, 944 mAh·g−1, and 751 mAh·g−1 at 0.2 A·g−1, 0.3 A·g−1, 0.5 A·g−1, and 1.0 A·g−1, respectively. Moreover, the reversible capacities could return to 870 mAh·g−1, 996 mAh·g−1, and 1027 mAh·g−1 when current densities returned to 0.5, 0.3, and 0.2 A·g−1, respectively.