Fast Charging of Energy-Dense Lithium Metal Batteries in Localized Ether-Based Highly Concentrated Electrolytes

Li metal batteries (LMBs) employing high voltage cathodes show promise as next generation batteries for electric vehicles due to their high energy density. However, the cycling stability of such energy-dense LMBs at high charge rates has seldom been explored. In this work, Li Coulombic efficiency (CE) as a function of current density (i.e., C-rate) and temperature was investigated in ether-based highly concentrated electrolytes (HCEs). We found that Li metal anodes can be stably cycled in the HCEs at elevated temperatures with a high Li CE of >99.4% for a plating capacity of 3 mAh cm −2 at a high C-rate greater than 1 C. The cycling stability of LMB full cells with Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 (NMC811) cathodes was also investigated at different charge rates (1 C to 3 C) at 40 and 60 °C. The LMBs with high areal capacity (∼3.2 mAh cm −2 ) NMC811 cathodes and minimal Li excess anodes (negative/positive capacity ratio (N/P ratio) <3.1) can achieve ∼189 stable cycles with an average efficiency of ∼99.86% at 1 C charge and C/3 discharge at 60 °C.