Enabling High Capacity and Coulombic Efficiency for Li-NCM811 Cells Using a Highly Concentrated Electrolyte

Lithium metal batteries suffer from dendrite formation and the associated safety hazards of thermal runaway reactions. In this study, we report the performances of a highly concentrated electrolyte (HCE) and a dilute LiPF₆ electrolyte in lithium metal cells using LiNi_0.8Co_0.1Mn_0.1O₂. While the HCE exhibits lower bulk ionic conductivity than the dilute LiPF₆ electrolyte, the cell conductivity is higher for the HCE system, indicating higher thermodynamic stability of the electrolyte against the electrodes. Full cell cycling demonstrates higher capacity for the HCE system, which declines as a function of cycle number due to the formation of decomposition products, similar to the dilute LiPF₆ system. The origin of the enhanced performance is the higher stability of the HCE against a Li metal anode as compared to the dilute LiPF₆ electrolyte. Cycling at higher temperatures further enhances the performance of the HCE, which is more thermally stable than the dilute LiPF₆ electrolyte.