Phase-Structure Modulated Self-Supporting Indium-Bismuth Alloy Films as Anodes for Advanced Magnesium Ion Batteries

Alloy-type anodes used in magnesium ion batteries (MIBs) have garnered significant attention in light of their substantial theoretical specific capacities and possible matchability with conventional electrolytes. However, the major challenges for alloy-type anodes are the sluggish transport kinetics as well as severe volume variations during the discharge/charge processes. Herein, we present a strategy for phase-structure modulation to fabricate a self-supporting In-Bi film through straightforward magnetron sputtering. In comparison to the single-phase In and Bi electrodes, the biphase InBi/Bi electrode displays markedly enhanced rate and cycling performance, with the discharge capacities of 303.1/292.6 mAh g^-1 after 550/500 cycles at 200/2000 mA g^-1, respectively. The exceptional Mg storage capability of the sputtered InBi/Bi electrode could be ascribed to the favorable two-phase configuration and increased phase boundaries, effectively accommodating volume expansion and accelerating Mg²⁺ ion transport. More importantly, the (de)magnesiation mechanism of InBi/Bi for MIBs was elucidated through operando X-ray diffraction.