Phase-boundary regulation boosting electrochemical reactivity of tin-based anodes for magnesium-ion batteries

Tin(Sn)-based materials are promising anodes for magnesium-ion batteries(MIBs) owing to their low reaction voltages, high theoretical specific capacities and good compatibility with conventional electrolytes. However, relatively arduous alloying reaction and sluggish diffusion kinetics limit their practical applications. Herein, we proposed a general strategy to regulate the electrochemical reactivity and performance of Sn-based anodes for Mg storage through the introduction of the second phase and phase boundary. The biphase Sn–Al, Sn–Pb and Sn–Zn O films were further fabricated via magnetron co-sputtering. Taking Sn–Al as an example, it has been revealed that the introduction of Al can effectively stimulate the electrochemical reaction of Sn with Mg in either nanoscale or bulk through combining experiments with density-functional theory calculations. Specially, the rolled Sn–Al electrode exhibits superior long-term stability over 5,000 cycles. Additionally, the Mg-storage mechanism of the Sn–Al electrode was investigated by operando X-ray diffraction. The Sn–Al anodes also demonstrate good compatibility with simple Mg-salt-based electrolytes like Mg(TFSI)2in full cells. More importantly, it has been authenticated that the activation effect of second phase and phase boundary to Sn is also applicable to Pb and Zn O. Our findings may provide a favorable reference for the development of alloy-type anodes for MIBs.