Quasi-Localized High-Concentration Electrolytes for High-Voltage Lithium Metal Batteries

The poor compatibility with Li metal and electrolyte oxidation stability preclude the utilization of commercial ester-based electrolytes for high-voltage lithium metal batteries. This work proposes a quasi-localized high-concentration electrolyte (q-LHCE) by partially replacing solvents in conventional LiPF6 based carbonated electrolyte with fluorinated analogs (fluoroethylene carbonate (FEC), 2,2,2-trifluoroethyl methyl carbonate (FEMC)) with weakly-solvating ability. The q-LHCE enables the formation of an anion-rich solvation sheath, which functions like LHCE but differs in the partial participation of weakly-solvating cosolvent in the solvation structure. With this optimized electrolyte, inorganic-dominated solid electrolyte interphases are achieved on both the cathode and anode, leading to uniform Li deposition, suppressed electrolyte decomposition and cathode deterioration. Consequently, q-LHCE supports stable cycling of Li | LiCoO2 (& AP;3.5 mAh cm(-2)) cells at 4.5 V under the whole climate range (from -20 to 45 & DEG;C) with limited Li consumption. A practical ampere-hour level graphite | LiCoO2 pouch cell at 4.5 V and aggressive Li | LiNi0.5Mn1.5O4 cell at 5.0 V with excellent capacity retention further reveals the effectiveness of q-LHCE. The refinement of old-fashioned carbonate electrolytes provides new perspectives toward practical high-voltage battery systems.