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

摘要

The poor compatibility with Li metal and electrolyte oxidation stabilitypreclude the utilization of commercial ester-based electrolytes for high-voltagelithium metal batteries. This work proposes a quasi-localizedhigh-concentration electrolyte (q-LHCE) by partially replacing solvents inconventional LiPF_6 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 ofan anion-rich solvation sheath, which functions like LHCE but differs in thepartial participation of weakly-solvating cosolvent in the solvation structure.With this optimized electrolyte, inorganic-dominated solid electrolyteinterphases are achieved on both the cathode and anode, leading to uniformLi deposition, suppressed electrolyte decomposition and cathodedeterioration. Consequently, q-LHCE supports stable cycling of Li | LiCoO_2(≈3.5 mAh cm~(?2)) cells at 4.5 V under the whole climate range (from ?20 to45 ℃) with limited Li consumption. A practical ampere-hour level graphite |LiCoO_2 pouch cell at 4.5 V and aggressive Li | LiNi_(0.5)Mn_(1.5)O_4 cell at 5.0 V withexcellent capacity retention further reveals the effectiveness of q-LHCE. Therefinement of old-fashioned carbonate electrolytes provides new perspectivestoward practical high-voltage battery systems.