Locally Competitive Coordination Electrolyte for High‐Voltage Lithium‐Metal Batteries With Ni‐Rich Cathodes

ABSTRACT Lithium (Li) metal anodes (LMAs) hold great promise to increase the energy density of batteries. This is especially true when using an energy‐dense cathode such as Ni‐rich layered transition metal oxides, but unfortunately, these lead to accelerated capacity loss when combined with LMAs. Ni‐rich cathodes suffer from surface reduction, which can be accelerated in contact with certain electrolyte solvents. This in turn leads to transition metal dissolution and shuttling, which poisons the solid electrolyte interphase (SEI) and complicates the anode stabilization. Here, we propose nitrile primary solvent combined with ether co‐solvent, diluent and two borate salts to suppress parasitic reaction. A competition in the ion coordination between solvents surrounded by diluents is achieved. This leads to the anions being preferentially decomposed in the SEI and enhanced reversibility. Using high cathode areal capacity (4.0 mAh cm − 2 ), thin LMAs (N/p = 2.5), lean electrolyte (3 g Ah − 1 ), and high charging voltages (≥4.4 V), we achieve a capacity retention of 80% over 250 cycles. With moderately high loading cathode (3.4 mAh cm − 2 ) but higher upper voltage (4.6 V), the cells retain 87.5% capacity retention over 430 cycles. Finally, we demonstrate Ah‐level anode‐free pouch cells with a 78.7% capacity retention over 100 cycles.