A Bifunctional Imidazolyl Iodide Mediator of Electrolyte Boosts Cathode Kinetics and Anode Stability Towards Low Overpotential and Long‐Life Li‐O ₂ Batteries

Abstract 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 2 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 2 batteries. The anion I − can effectively promote the charge transport of Li 2 O 2 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 2 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 Li 2 O 2 yield further proves the reversible generation/decomposition of Li 2 O 2 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 2 batteries.