Trace ethylene carbonate-mediated low-concentration ether-based electrolytes for high-voltage lithium metal batteries

Abstract

Ether-based electrolytes have been extensively utilized in lithium metal batteries due to their superior compatibility with lithium metal. Nevertheless, the inferior high-voltage oxidation stability (>4.0 V) hampers their practical implementation and proves challenging to rectify without resorting to high-concentration strategies or the inclusion of specific additives. Herein, it was discovered that the ether-based electrolytes can be well-stabilized by adding a trace amount of ethylene carbonate (EC) at a low concentration (i.e., 0.63 M). This strategy can not only improve the solubility of LiPF₆ in dimethoxyethane (DME) solvent significantly, but also improve the high-voltage oxidation stability of the electrolyte, enabling the 80 μm Li‖LiNi_0.8Co_0.1Mn_0.1O₂ full-cell to operate stably at 4.5 V. We demonstrated that the EC can preferentially dissociate the insoluble LiPF₆ by entering the first solvation layer, which further regulates the molecule–ion interaction on the cathode interface to improve the oxidation stability of the electrolyte. A novel solvation structure and interfacial model were proposed to elucidate the solubilization effect and interpret the superior battery performance at the molecular scale. This work not only sheds light on the electrolyte's microstructures in their formulation but also offers a promising strategy to overcome the challenges associated with high-energy-density lithium (ion) batteries.