Achieving high-energy-density magnesium/sulfur battery via a passivation-free Mg-Li alloy anode

Magnesium/sulfur batteries have emerged as one of the considerable choices for next-generation batteries. However, its low voltage platform caused by the passivation of magnesium anode limits its actual energy density. Herein, a magnesium-lithium alloy is screened out as a passivation-free anode, which hinders the passivation reaction on the anode through the substitution reaction between lithium in the alloy and the magnesium ions in the electrolyte. The alloy anode exhibits an improved interfacial reaction kinetics, and the impedance is reduced by 5 orders of magnitude compared to that of magnesium anode. With passivation-free Mg-Li alloy anode, the magnesium/sulfur battery achieves an enhanced discharge voltage platform of 1.5 V and an energy density of 1829 Wh kg⁻¹. This study provides a novel design of passivation-free magnesium alloy anode for high-energy-density magnesium/sulfur batteries.