Wide-Temperature, High-Voltage, Flame-Retardant Electrolyte for 4.8 V Li||NCM94 Batteries

All-climate lithium metal batteries attract great interest, but their poor safety and cycling performance hinder their applications, especially with high cut-off voltage nickel-rich layered oxide cathode. Herein, we develop a high-voltage, wide-temperature, and flame-retardant electrolyte for Li|| LiNi_0.94Co_0.05Mn_0.01O₂ (NCM94) batteries with excellent cycling performance through constructing highly Li⁺-conductive, lithophilic gradient cathode electrolyte interphase (CEI). Such CEI exhibits a gradual decrease in C─F and a gradient increase in LiF and LiB_xO_y from the outside to the inside, which effectively inhibits structural degradation of the NCM94 cathode. With an excellent CEI, Li|| NCM94 batteries show outstanding cycling stability and wide temperature applicability (-40∼60 °C). The battery could exhibit a capacity retention of 87% after 200 cycles at 4.8 V, and deliver 112% (or 56%) of their room-temperature capacity at 60 °C and -40 °C, respectively. Furthermore, as-constructed 7.6 Ah pouch cell could run 145 cycles with an energy density of 541 Wh kg^-1. This work provides the guidance on designing electrode-electrolyte interfaces for wide-temperature, high-voltage lithium metal batteries.