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

The aprotic lithium‐oxygen (Li−O 2 ) 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 Li 2 O 2 products is a major obstacle for realizing the high energy efficiency and long cycle life. Here, we report a new Cl − /Cl 3 − 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 Li 2 O 2 to LiOH and provides new insights toward the role of redox mediators through the addition of Cl − in Li−O 2 battery systems.