Electrochemical performance of Mg-Sn alloy anodes for magnesium rechargeable battery

Abstract

Mg metal has been used as an anode material for Mg-ion rechargeable batteries (MRBs), but the undesired passivation layer between Mg and electrolyte indeed limits the further development of MRBs. Replacing Mg with Sn and Mg2Sn has been proved to be an alternative for Mg ions storage based on the alloying reaction between Mg and Sn. In the present study, we have investigated the electrochemical performance of hypoeutectic Mg-Sn alloy anodes with an all-phenyl complex (APC) electrolyte. The microstructure and electrochemical results indicate that the Mg14Sn alloy anode displays different electrochemical behaviors of Mg stripping/plating due to the formation of eutectic (α-Mg+Mg2Sn) phase. Special anodic peaks, different reaction sites and high overpotential are observed in the Mg14Sn alloy anode. Electrochemical impedance spectroscopy (EIS) results show that the anode-electrolyte interface is significantly affected by the addition of Sn. Mg14Sn alloy anode shows much lower resistance than pure Mg after 30 cycles. The results obtained from electron microscopic observations confirm that the formation of nanosized β-Sn stems from the eutectic phase.