A Bifunctional Imidazolyl Iodide Mediator of Electrolyte Boosts Cathode Kinetics and Anode Stability Towards Low Overpotential and Long-Life Li-O Batteries.

The addition of a redox mediator as soluble catalyst into electrolyte can effectively overcome the bottlenecks of poor energy efficiency and limited cyclability for Li-O batteries caused by passivation of insulating discharge products and unfavorable byproducts. Herein we report a novel soluble catalyst of bifunctional imidazolyl iodide salt additive, 1,3-dimethylimidazolium iodide (DMII), to successfully construct highly efficient and durable Li-O batteries. The anion I can effectively promote the charge transport of LiO and accelerate the redox kinetics of oxygen reduction/oxygen evolution reactions on the cathode side, thereby significantly decreasing the charge/discharge overpotential. Simultaneously, the cation DMI forms an ultrathin stably solid-electrolyte interphase film on Li metal, greatly inhibiting the shuttle effect of I and improving the stability of anode. Using this DMII additive, our Li-O batteries achieve an extremely low voltage of 0.52 V and ultra-long cycling stability over 960 h. Notably, up to 95.8 % of the LiO yield further proves the reversible generation/decomposition of LiO without the occurrence of side reactions. Both experimental and theoretical results disclose that DMII enables Li easily solvated, testifying the dominance of the solution-induced reaction mechanism. This work provides the possibility to design the soluble catalysts towards high-performance Li-O batteries.