Efficient Stress Dissipation in Well‐Aligned Pyramidal SbSn Alloy Nanoarrays for Robust Sodium Storage

Alloy‐type anode materials are promising for sodium‐ion batteries owing to their high theoretical specific capacity. However, their practical application is limited by the rapid capacity decay resulted from drastic volume change upon sodium (Na) alloying/dealloying. Here, a facile fabrication of well‐aligned antimony tin (SbSn) alloy nanoarrays electrodeposited on copper (Cu) substrates is reported. Such a binary alloy possesses well‐defined triangular pyramid‐like structure, and the subsequent thermal annealing process develops an “alloy glue” at the root of the nanoarrays which generates a strong connection between the active alloy and the copper substrate. Density functional theory calculation results suggest that the as‐fabricated alloy offers an energetically favorable Na diffusion as compared to the individual metals, and the “alloy glue” provides a strong interaction between the substrate and SbSn. More importantly, based on finite‐element analysis, such a unique construction of the triangular pyramid‐like nanostructure not only creates a small difference in the Na+ concentration gradient, but also builds a uniform stress distribution that promotes both highly efficient Na+ diffusion and effective stress dissipation. Collectively, the optimized composition and geometry give rise to the enhanced high‐rate performance and prolonged cycle life of the current SbSn alloy nanoarrays.