A dual-function additive strategy for stabilizing magnesium metal interfaces

초록

Rechargeable magnesium batteries have emerged as promising next-generation energy storage systems owing to the high volumetric capacity and dendrite-free deposition behavior of Mg metal. However, the practical implementation of chloride-free Mg electrolytes remains limited by unstable Mg metal interfaces. Strong Mg2+-anion interactions and the presence of trace impurities induce surface passivation, leading to sluggish kinetics and poor reversibility. Here, we present a rational additive strategy to regulate interfacial reactions in a Mg(TFSI)2/diglyme electrolyte using trimethylsilyl imidazole (TMSI). Comprehensive spectroscopic analysis reveals that TMSI modulates the local electronic environment of Mg2+, forming a regulated Mg2+ coordination environment that suppresses direct Mg2+-anion interaction while preserving the primary coordination between Mg2+ and glyme molecules. Concurrently, TMSI effectively scavenges residual water, suppressing impurity-driven parasitic decomposition. By simultaneously modulating the solvation structure and mitigating degradation from trace contaminants, the additive fundamentally reshapes interfacial evolution during Mg plating/ stripping. This dual regulation reduces polarization and enables controlled interphase formation, ultimately enhancing electrochemical reversibility. Consequently, the modified electrolyte facilitates highly reversible Mg deposition under diverse operating conditions without compromising bulk ionic transport properties. These findings establish a practical dual-function additive approach for stabilizing chloride-free Mg electrolytes and offer valuable design principles for advanced multivalent battery systems.

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