The Impact of Crystal Structure on the Electrochemical Performance of Silicon–Carbon Anodes

Silicon–carbon (Si/C) materials have been regarded as the next‐generation anode material for lithium‐ion batteries due to their high specific capacity. However, their practical application is hindered by rapid capacity fading caused by the significant volume expansion of Si. This work systematically investigates the influence of the crystalline structure of the Si phase on the electrochemical performance of Si/C anode materials. Using crystalline silicon–carbon (c‐Si/C) and amorphous silicon–carbon (a‐Si/C) as model systems, the study finds that the a‐Si/C anode material with an isotropic amorphous structure possesses a higher lithium‐ion diffusion coefficient and forms a more stable interfacial film, effectively suppressing electrolyte side reactions and active material loss. In contrast, c‐Si/C suffers from inhomogeneous lithiation, stress concentration, and repeated solid–electrolyte interphase (SEI) fracture due to its crystalline anisotropy. As a result, a‐Si/C exhibits an outstanding capacity retention of 83.4% after 150 cycles at 2 A g −1 , and the electrode expansion rate of a‐Si/C is only 37%, which is lower than the 51% observed for c‐Si/C. This study clarifies the influence of the crystallinity of the silicon phase on capacity decay behavior, providing a theoretical basis for the rational design of high‐performance Si/C anode materials.