Chloride Ion as Redox Mediator in Reducing Charge Overpotential of Aprotic Lithium–Oxygen Batteries

Abstract

The aprotic lithium‐oxygen (Li−O2) battery with a high theoretical energy density has been considered as a promising candidate for next‐generation energy storage devices. However, the formation of insulating Li2O2 products is a major obstacle for realizing the high energy efficiency and long cycle life. Here, we report a new Cl−/Cl3− redox mediator to reduce the charge overpotential by a facile introduction of chloride ion (Cl−) additives into the organic electrolyte. The redox mediator can effectively promote the formation of the LiOH discharge product, and facilitate efficient LiOH decomposition. Therefore, the cell with the Cl− additives possesses a significantly low charge overpotential of 0.29 V, an extended cycle life (up to 71 cycles) at a rate of 500 mA g−1 with a fixed capacity of 500 mAh g−1, and an enhanced rate capability. This study offers an effective approach to modulate discharge products from Li2O2 to LiOH and provides new insights toward the role of redox mediators through the addition of Cl− in Li−O2 battery systems.