Sn is a most promising anode candidate for Na-ion battery, due to its high capacity (847 mAh/g or 1210 Ah/L) and low average operating voltage (~0.25 V vs. Na/Na⁺). However, its cycle stability is limited by significant volume change, stress built-up, and Sn aggregation during charge/discharge cycles.

The present work attempted to tackle this outstanding problem by introducing other elements to form binary or ternary Sn-based alloys. Although the cycling stability of the Sn-based alloy were significantly improved when compared to pure Sn metal, we found that continuous segregation of Sn from the alloy during the cycling process remained a major problem, causing the deterioration of the alloy anode. We showed that a few other approaches can further enhance the cycling stability of the Sn-based alloys. In many cases, a compromise is needed between the capacity and cycle stability of the alloy anode.

This work is supported by RGC/GRF under project No. 14316716