Origins of Abrupt Capacity Degradation in Lithium‐Ion Batteries with Silicon‐Based Anodes

Abstract The incorporation of silicon monoxide (SiO) into graphite anodes improves the energy density of lithium‐ion batteries. However, it falls short of the long‐term durability of pure graphite, and research on their cycling performance remains limited. This study observes a sudden capacity decay in graphite/SiO anodes during long‐term cycling at room temperature (RT) and a moderate C‐rate. This decay arises from the mechanical degradation of SiO, leading to the formation of a “SiO‐SEI crust” that consumes lithium ions. This phenomenon does not occur at higher temperatures or lower C‐rates, implying that larger diffusion‐induced stress from lithium‐ion gradients at RT and 1 C accelerates SiO degradation. Furthermore, introducing a relaxation step to reduce the lithium‐ion gradient mitigates this sudden capacity decay, supporting diffusion‐induced stress as a critical factor in the degradation mechanism. These findings emphasize the role of diffusion‐induced stress in the performance degradation of Si‐based batteries and provide valuable insights for enhancing the lifespan of composite anodes.