Self-supporting, eutectic-like, nanoporous biphase bismuth-tin film for high-performance magnesium storage

Magnesium ion batteries are emerging as promising alternatives to lithium ion batteries because of their advantages including high energy density, dendrite-free features and low cost. Nevertheless, one of the major challenges for magnesium ion batteries is the kinetically sluggish magnesium insertion/extraction and diffusion in electrode materials. Aiming at this issue, biphase eutectic-like bismuth-tin film is designed herein to construct a self-supporting anode with interdigitated phase distribution and hierarchically porous structure, and further fabricated by a facile one-step magnetron cosputtering route. As benchmarked with single-phase bismuth or tin film, the biphase bismuth-tin film delivers high specific capacity (538 mAh/g at 50 mA/g), excellent rate performance (417 mAh/g at 1, 000 mA/g) and good cycling stability (233 mAh/g at the 200th cycle). The superior magnesium storage performance of the sputtered bismuth-tin film could be attributed to the synergetic effect of the interdigitated bismuth/tin phase distribution, hierarchically porous structure and biphase buffering matrices, which could increase ionic transport channels, shorten diffusion lengths and reduce total volume changes.