Interface engineering strategy via electron-defect trimethyl borate additive toward 4.7 V ultrahigh-nickel LiNi0.9Co0.05Mn0.05O2 battery

The Li metal battery with ultrahigh-nickel cathode(LiNixM1-xO2, M = Mn, Co, and x ≥ 0.9) under high-voltage is regarded as one of the most promising approaches to fulfill the ambitious target of 400 Wh/kg.However, the practical application is impeded by the instability of electrode/electrolyte interface and Ni-rich cathode itself. Herein we proposed an electron-defect electrolyte additive trimethyl borate(TMB)which is paired with the commercial carbonate electrolyte to construct highly conductive fluorine-and boron-rich cathode electrolyte interface(CEI) on LiNi0.9Co0.05Mn0.05O2(NCM90) surface and solid electrolyte interphase(SEI) on lithium metal surface. The modified CEI effectively mitigates the structural transformation from layered to disordered rock-salt phase, and consequently alleviate the dissolution of transition metal ions(TMs) and its “cross-talk” effect, while the enhanced SEI enables stable lithium plating/striping and thus demonstrated good compatibility between electrolyte and lithium metal anode. As a result, the common electrolyte with 1 wt% TMB enables 4.7 V NCM90/Li cell cycle stably over 100 cycles with 70% capacity retention. This work highlights the significance of the electron-defect boron compounds for designing desirable interfacial chemistries to achieve high performance NCM90/Li battery under high voltage operation.