Lithium Nitrate-Mediated Low-Volatile Deep Eutectic Electrolyte for Highly Stable Lithium–Oxygen Batteries

Lithium–oxygen batteries (LOBs), with an extremely high theoretical energy density (3500 Wh kg–1), have been regarded as potential candidates for future large-scale energy storage facilities. However, the unique semiopen system puts a hurdle on the long-lasting operation of LOBs with critical issues like the severe volatilization of the aprotic electrolyte, surface passivation or dendrite growth of the lithium metal anode, and the sluggish oxygen redox reactions. Herein, we propose a strategy to tackle the above issues with a solvation structure regulated deep eutectic electrolyte (DEE) for LOBs. With modulated content of LiNO3 as the interface stabilizer, the Li/NMA-2.0/Li symmetric cell achieves a prolonged cycling stability of over 700 h under a semiopen O2 atmosphere. It can also operate in real air, while the good high temperature conductivity of the electrolyte enables the battery to cycle for more than 100 times at 60 °C. Besides, the solvation structure of the DEE electrolyte alters the discharge/charge reaction kinetics via lowering the nucleation energy of Li2O2, achieving the formation of nanoscale discharge products and realizing a superlong cyclability of 779 cycles at a high current density of 500 mA g–1. Moreover, the underlying mechanisms are well revealed through systematically designed experiments and theoretical simulations. This work will provide guidance in designing electrolytes for alkali-metal batteries and semiopen electrochemical systems.