Towards Safe Rechargeable K-O2 Batteries

Metal-air batteries are promising future energy storage systems. However, they generally have high overpotentials caused by the multi-electron redox processes oxygen goes through in order to store and dispense energy. Therefore, the round-trip energy efficiency is undermined, and the parasitic reactions of electrolyte and carbon electrode cause the decay of capacity and limit the battery life. Here, a K–O₂ battery is report that uses K⁺ ions to capture O₂^- to form the thermodynamically stable KO₂ product. This allows for the battery to operate through the one-electron redox process of O₂/ O₂^-. Without the use of catalysts, the battery shows a low discharge/charge potential gap of less than 50 mV at a modest current density. In addition, I will report our recent detailed studies of the side reactions that limit the cycle life of the K–O₂ battery, and discuss some methods to address these challenges. I will also address the safety issue considering the use of K metal electrode.