Phase engineering in lead–bismuth system for advanced magnesium ion batteries

Abstract

Rechargeable magnesium ion batteries (MIBs) have aroused great interests, but their development is restrained by the incompatibility of Mg metal anodes with conventional electrolytes. Replacing Mg metal with alloy anodes is a promising strategy to address this incompatibility issue. Based on phase engineering, we designed and fabricated a biphase Pb_0.7Bi_0.3/Bi film by a facile magnetron co-sputtering route. Compared with single-phase Pb, Bi and Pb_0.7Bi_0.3 films, the biphase Pb_0.7Bi_0.3/Bi electrode delivers significantly enhanced cycling stability and rate performance, which could be attributed to the biphase buffer matrix mitigating large volume variations and favorable phase boundaries accelerating Mg²⁺ ion transport. Furthermore, the Mg storage mechanism of Pb_0.7Bi_0.3 and Pb_0.7Bi_0.3/Bi films was investigated using operando X-ray diffraction experiments and density functional theory calculations. More importantly, the biphase Pb_0.7Bi_0.3/Bi electrode exhibits good compatibility with conventional electrolytes like Mg(TFSI)₂.