Chloride-Free Electrolyte Regulated by Triphenyl-Metallic Additive for Anti-Passivated and Reversible Mg Metal Anodes

Abstract

Rechargeable magnesium batteries (RMBs) have attracted extensive attention due to the high volumetric capacity and natural abundance of magnesium (Mg) metal anode. However, the Mg metal anode in ether-based electrolyte systems often suffers from surface passivation, leading to the irreversible plating/stripping behavior of Mg. In this work, for the first time, an effective strategy is proposed to modify the Mg metal anode by in situ alloy formation using a chlorine-free organic metal compound, triphenyl bismuth (TPB). Through electrochemical reduction, an Mg-Bi alloy forms uniformly on the Mg metal anode surface, providing abundant nucleation sites for Mg, allowing for smooth and stable Mg deposition and suppressing the occurrence of short circuits. In a 1,2-dimethoxyethane (DME)-based electrolyte system, the addition of TPB significantly improves the electrochemical performance of Mg anode, enabling stable cycling for up to 170 h at a low overpotential. Similarly, in the tetraethylene glycol dimethyl ether (G4) electrolyte system, excellent performance is observed, achieving stable cycling of 240 h. This work confirms the feasibility of using chlorine-free organic metal additives to improve the Mg anode interface and provides new possibilities for enhancing the practical applications of RMBs.