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 (LiNi x M 1− x O 2 , 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 LiNi 0.9 Co 0.05 Mn 0.05 O 2 (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.