Electrolyte additive engineering to construct stable interphases with high ionic conductivity for high-temperature and high-voltage lithium metal batteries

Integrating high-voltage nickel-rich cathodes with lithium metal anodes while elevating charging cut-off voltage is a practical strategy for constructing high-energy-density battery systems. Nevertheless, severe structural degradation of cathodes and aggressive electrode/electrolyte interfacial reactions hinder their application. Worse still, these issues are exacerbated under high-voltage and high-temperature operating conditions. Herein, we propose a bifunctional electrolyte with 4-trifluoromethylbenzeneboronic acid neopentyl glycol ester (TFMB) as an additive to tailor robust interphases, which alleviates cathode structural damage and suppresses lithium dendrite growth. The electron-deficient boron in TFMB coordinates with anions, thereby enhancing the thermal stability of electrolytes and facilitating the involvement of anions in the formation of interphases. Meanwhile, fluorinated functional groups contribute to the formation of stable, inorganic-rich interphases and further boost the high-voltage resistance of batteries. Therefore, Li‖Ni_0.8Co_0.1Mn_0.1O₂ (NCM811) cells maintain a superior reversible capacity retention of 75.25% after 300 cycles at 4.5 V and achieve outstanding cycling stability with 80% capacity retention over 120 cycles at 4.7 V. Impressively, Li‖NCM811 cells demonstrate favorable capacity retention even at 50 °C, validating their application prospects. Furthermore, its good compatibility with LiFePO₄ cathodes meets the demands of different energy scales. This work provides meaningful insights for designing high-voltage and high-temperature electrolytes for lithium metal batteries.