MOF-Based Separator in an Li–O2 Battery: An Effective Strategy to Restrain the Shuttling of Dual Redox Mediators

Tuning the electrochemical formation/decomposition of Li2O2 from the circumscribed surface pathways to the solution ones, the dual redox mediator (RM) strategy largely promotes the discharge capacity and reduces the charge overpotential in aprotic Li–O2 batteries, revealing a promising strategy to realize anticipated high specific energy cycling. However, both RM-induced Li degradation and electron shuttling between the cathode and anode become the become the inherent defects, resulting in poor sustainability. Here, with a narrow pore size window, a metal–organic framework (MOF)-based separator has been proposed, which acts as a RM molecule sieve to restrain the shuttling. By maximizing the advantages of the dual RM strategy, the Li–O2 cell reveals a prolonged cycled life (100 cycles, 5000 mAh g–1) at high current rate (1000 mA g–1). Moreover, the Li–O2 pouch cell fabricated by the flexible MOF-based separator exhibits the potential for the development of large-scale energy storage devices.