New Insights on the Good Compatibility of Ether-Based Localized High-Concentration Electrolyte with Lithium Metal

Localized high-concentration electrolytes (LHCEs) have captured considerable attention, since they retain the merits of high-concentration electrolytes while circumventing the disadvantages of high viscosity and high costs. Herein, a systematic comparison between two representative LHCEs (i.e., dimethyl carbonate (DMC)-based LHCE and 1,2-dimethoxyethane (DME)-based LHCE) in high-voltage Li metal batteries was performed. The results showed that DME-based LHCE possesses better compatibilty with Li metal anodes than DMC-based LHCE, and the underlying mechanism is clarified from the point of solid electrolyte interphase (SEI) formation. The two representative LHCEs showed comparable reductive stability, while Li+–DME showed better reductive stability than Li+–DMC. This means the more prominent decomposition of anions in DME-based LHCE, since SEI is derived from the competitive decomposition products of solvents and anions, which is further verified by the more-complete anion decomposition products found in SEI formed in DME-based LHCE. The inorganic-rich SEI with superior passivating ability is reponsible for the good compatibility of DME-based LHCE with Li metal anodes. The findings in this study provides fresh understandings on the stable nature of ether-based LHCE with Li metal anodes, which can serve as guidelines for advanced electrolytes engineering.