Constructing an enhanced charge-mass transfer passage for silicon anodes to achieve increased capacity under high-rate conditions

Abstract

Silicon (Si) holds promise as an anode material for next-generation lithium-ion batteries due to its high theoretical capacity. However, practical applications are impeded by structural damage from volume expansion. Here, we designed a novel Si/CNFs/C anode by integrating mesoporous Si particles, carbon nanofibers (CNFs), and carbon quantum dots into a three-dimensional (3D) architecture via a one-step magnesiothermic reduction process. This design significantly enhances both electron and ion conductivity, alleviates the volume expansion of Si particles, and ensures mechanical stability during battery operation. Consequently, batteries with the Si/CNFs/C anode exhibit a reversible capacity of 1,172.4 mAh g-1 after 200 cycles at 0.1 A g-1 and maintain 1,107.7 mAh g-1 after 1,000 cycles at 1 A g-1. Notably, after 1,000 cycles at a high current density of 1 A g-1, the capacity remains nearly comparable to that after 100 cycles at 0.1 A g-1, attributed to significant pseudocapacitive characteristics that facilitate high performance under elevated current densities. Furthermore, we employed distribution of relaxation times analysis alongside other electrochemical techniques to investigate changes in ion transport pathways and the evolving role of Si in the energy storage process. Our design and analysis provide valuable insights for optimizing 3D conductive architectures and understanding the dynamic electrochemical mechanisms of Si-based anodes, advancing the development of high-performance lithium-ion batteries.