Interfacial stabilization enabled by triethyl borate for high-voltage batteries with a wide temperature range

Coupling ultrahigh-nickel LiNi_0.9Co_0.05Mn_0.05O₂ (NCM90) cathodes with lithium metal anodes is a promising strategy toward high-energy-density batteries. However, its practical implementation is severely restricted by aggressive parasitic reactions at the electrode/electrolyte interface. Herein, triethyl borate (TEB), a novel multifunctional electrolyte additive, is adopted to markedly enhance the electrochemical performance of Li‖NCM90, even under high cut-off voltage and across a wide temperature range. The electron-deficient boron center in TEB acts as an efficient anion receptor to scavenge HF, thereby suppressing transition metal dissolution. Meanwhile, TEB facilitates the formation of a compact, thin, and highly conductive B–O/B–F-rich cathode–electrolyte interphase (CEI) and a solid electrolyte interphase (SEI), which effectively alleviates interfacial degradation, accelerates Li⁺ transport, and suppresses lithium dendrite growth. As expected, Li‖NCM90 cells with the TEB additive deliver a high initial specific capacity of 214.45 mAh g⁻¹ even at 4.6 V and 2C with stable cycling over 200 cycles. Excitingly, the cells still deliver considerably higher specific capacities at −30 °C (127.4 mAh g⁻¹) and 50 °C (220.01 mAh g⁻¹) along with excellent cycling stability. Encouragingly, the pouch cell also exhibits outstanding reversible capacity and long cycling stability. The facile additive strategy provides a promising pathway for the practical development of high-energy-density batteries.