Preparation of Carbon-Silicon Composites by Potassiothermic Reduction of Silicon Tetrachloride and Their Electrochemical Performance

The traditional graphite electrode materials can't meet the needs of the Liion batteries with high energy density because of its low specific capacity. It is of great practical significance to modify the traditional graphite electrode materials and improve their specific capacity. In this paper, a simple potassiothermic reduction of silicon tetrachloride method is used to recombine silicon onto the conventional graphite electrode materials, which greatly improves the specific capacity and the cycling performance of the electrode materials. When the content of silicon in the carbon-silicon (C/Si) composites is 8.5%, the theoretical specific capacity of the obtained C/Si composites is 644.6 mAh g–1, and after 1000 cycles of charge and discharge, the actual specific capacity is 570 mAh g–1, which is about 88.4% of the theoretical specific capacity; when the content of silicon in the C/Si composites is 19.0%, the theoretical specific capacity of the obtained C/Si composites is 981.33 mAh g–1, and after 1000 cycles of charge and discharge, the actual specific capacity can still reach 820 mAh g–1, which is about 83.6% of the theoretical specific capacity; when the content of silicon in the C/Si composites is 28.7%, the theoretical specific capacity of the obtained C/Si composites is 1292.4 mAh g–1, and after 1000 cycles of charge and discharge, the actual specific capacity is 710 mAh g–1, which is about 54.9% of the theoretical specific capacity; therefore, the optimal content of silicon in C/Si composites is about 19.0%. Through incorporating silicon into traditional graphite electrode materials via potassiothermic reduction of silicon tetrachloride, the specific capacity of the negative electrode is improved significantly, which is a better way to upgrade the products of the traditional graphite negative electrode materials manufacturers.