Ligand Impact of Silicanes as Anode Materials for Lithium-Ion Batteries

Two-dimensional allotropes of silicon-silicanes-show promise as anode materials for lithium-ion battery (LIB) applications in view of their predicted high specific capacities and layered structures that facilitate Li diffusion and avoid drastic volume change during battery cycling. Although recent studies improved the performance and stability of LIBs with silicane-based anodes, understanding of the silicane surface and crystalline evolution during lithiation/delithiation and the corresponding impacts on LIB performance remains lacking. Here, we describe a detailed investigation of the impact of surface functional groups and crystal evolution of a silicane anode during LIB operation. We demonstrate that silicanes co-passivated by hydride and hydroxyl ligands with a predesigned ratio have an improved theoretical specific capacity and better lithium diffusion properties. Combined spectroscopic and computational studies further indicate that the layered scaffold of silicane gradually converts to suboxide-based amorphous structures during initial cycles, which allows for efficient Li diffusion and boosts the specific capacity across the entire LIB operation. LIBs with silicane-based anodes achieve a maximum capacity of 1084 mA h/g at a current rate of 100 mA/g with improved stability (80% capacity retained after 160 cycles), indicating the potential of the tunable ligand passivation approach.