The design and regulation of porous silicon-carbon composites for enhanced electrochemical lithium storage performance

The combination of silicon and carbon materials which effectively relieve the volume expansion of silicon and improve the overall electrical conductivity is becoming one of the hot and widespread concern topics. In this research, the pitch was used as a carbon source to load a carbon layer on the surface of silicon, and a porous silicon-carbon anode material was prepared by etching the carbon layer and silicon with sodium hydroxide. The structure and electrochemical performance of porous silicon-carbon composite are further regulated by changing the carbonization temperature and softening point of pitch. The results revealed that appropriate porous structure and stability, as well as a high elastic carbon layer, contribute to the structural stability of the material after long cycles. The change in carbonization temperature regulates the graphitization degree and elasticity of the pitch-derived carbon layer, which would further affect the etching rate. High-softening point pitch has good thermal stability and forms a uniform and stable carbon layer. The porous Si-C composites with an optimized carbon layer exhibit a capacity retention rate of 89.4% after 300 cycles at a current density of 0.2 A g−1, showing excellent cycling stability.