Overcoming passivation in rechargeable magnesium batteries: Artificial solid-electrolyte interface for enhanced anode functionality

Abstract

Rechargeable magnesium batteries (RMBs) have garnered significant attention in the field of energy storage. However, the use of a traditional electrolyte, Mg(TFSI)2/DME, leads to the passivation of the Mg metal anode (MMA), limiting the reversible deposition and dissolution process of Mg2+. Consequently, we propose a feasible method to modify the MMA, resulting in the formation of an artificial solid-electrolyte interface (SEI) coating rich in MgBr2, MgI2 and Sb. This modification leads to substantial improvements in the interfacial kinetics and electrochemical properties of MMA, effectively suppressing the passivation reaction and significantly reducing the overpotential from 2 V to 0.3 V. Upon incorporating CuS/VS4 cathode materials with a 0.15 M SbBr3 modification, the discharge capacity reached 125 and 191 mAh·g−1, respectively (compared to the initial capacity of 30 and 98 mAh·g−1) after 30 cycles. Similarly, with a 0.8 M SbI3 modification, the battery exhibited capacities of 220 and 240 mAh·g−1, respectively. Through a combination of experimental and computational analyses, we confirmed the uniform distribution of Sb, MgBr2 and MgI2 on the MMA surface and a substantial decrease in the diffusion barrier of Mg2+. This study presents a straightforward and efficient method for constructing an artificial SEI coating.