Fabrication and electrochemical performance of Si-C composite nanostructures with SiO2 sacrificial agent for LIB anode

Silicon is widely considered as the most promising candidate for anode material in the next generation of lithium-ion batteries. However, the utilization of silicon as an anode is constrained due to its huge volume dilation upon lithiation. Repeated volume dilation upon lithiation and delithiation, destroys the anode assembly leading to capacity fade. In this work a porous Si-C nanostructure has been developed using amorphous SiO2 filler as sacrificial agent and preceramic polymer derived carbon as the conductive coating layer around nanoparticulate silicon. The synthesis of the proposed anode structure is easy, economic, and straight forward, which involves pyrolysis of a preceramic polymer coated Si/SiO2 composite and subsequent etching of the materials by HF. The hybrid anode structures were fabricated from materials pyrolyzed at two different temperatures of 1000 and 1200 ºC to study the effect of pyrolysis temperature on the structure and the electrochemical behaviour of the anodes. The final composites prepared at 1000 ºC delivered better electrochemical properties and displayed stable cycle life of 622 mAh g−1 for the 400th cycle at 0.1 A g−1 current density. The composite also exhibited better power capability of 229 mAh g−1 at 2 A g−1 rate. The synergistic combination of porous microstructure and interconnected network of the preceramic polymer-derived carbon accommodates the volume dilation of Si particles and enhances the conductivity of the anode structure.