NO ₃ ^– -Mediated Solvent Immobilization in Medium-Concentration Ether-Based Electrolytes: Enabling High-Voltage Lithium Metal Batteries with Wide Temperature Ranges

Ether-based electrolytes have been regarded as promising candidates for high-energy-density lithium metal batteries, yet they face significant challenges in maintaining stable cycling under high voltage (>4.3 V) and adapting to extreme environmental conditions. This study proposes an innovative solvent immobilization strategy to enhance the oxidative stability of ether electrolytes and stabilize interfaces with both lithium metal anodes and high-voltage cathodes. A unique "bead string" structure was formed by self-assembly of nitrate anion (NO₃^-) and long-chain ether solvent, effectively immobilizing solvent molecules in the bulk electrolyte. This structure facilitates the formation of an anion-rich electric double layer (EDL) at a medium electrolyte concentration (1.5 M), leading to the formation of a highly stable, inorganic-dominated passivation layer on the surfaces of both the lithium metal anode and high-voltage cathodes. The optimized electrolyte enables Li || LiCoO₂ and Li || NCM811 batteries to achieve exceptional cycling stability (81.8% capacity retention after 1400 cycles at 4.3 V and 73.4% capacity retention after 600 cycles at 4.45 V for Li || LiCoO₂; 79.8% capacity retention after 1500 cycles at 4.3 V for Li || NCM811). Moreover, the battery can operate across an ultrawide temperature range of -60 to 70 °C.