Optimizing the pore structure in silicon–carbon anodes: the impact of micropore and mesopore ratios on electrochemical performance†

Abstract

Silicon–carbon (Si/C) composites have attracted considerable attention as promising anode materials for high-energy-density lithium-ion batteries because of silicon's high theoretical capacity. However, the impact of the carbon material pore structure on the performance of Si/C composites remains poorly understood, posing a significant challenge in optimizing these materials. In this study, we synthesize Si/C anodes using a chemical vapor deposition (CVD) method, preparing carbon substrates with varying micropore and mesopore ratios through physical activation. By maintaining consistent silicon contents across all samples, we systematically investigate the relationship between the pore structure and key electrochemical performance metrics, including initial coulombic efficiency (ICE), rate capability, and cycling stability. Our findings reveal that carbon substrates with higher micropore content lead to the highest ICE, attributed to the uniform distribution of silicon within the matrix. Furthermore, while increased mesopore content initially enhances rate performance by facilitating lithium-ion transport, excessive mesopores reduce performance due to the aggregation of larger silicon particles and limited lithium-ion diffusion during dealloying. This study underscores the critical role of the pore structure in optimizing the electrochemical performance of Si/C anodes and provides valuable insights for designing high-performance silicon–carbon materials, thereby contributing to the advancement of next-generation lithium-ion batteries.