(Invited) Electrolyte Developments for Rechargeable K-O2 Batteries

Abstract

Oxygen is a crucial component in emerging technologies in energy conversion and storage. For example, Li–O2 battery is regarded as one of the most promising energy storage systems for future applications. However, its energy efficiency is greatly undermined by the large overpotentials of the discharge (formation of Li2O2) and charge (oxidation of Li2O2) reactions. The parasitic reactions of electrolyte and carbon electrode induced by the high charging potential cause the decay of capacity and limit the battery life. Here, I will present our systematic investigation of a K–O2 battery that uses K+ ions to capture superoxide (O2 -) to form the thermodynamically stable KO2 product. This allows for the battery to operate through the facile 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 this talk, I will emphasize our investigation of the side reactions between K metal and electrolytes and our development in electrolytes that suppress the side reactions. As the consequence, significant improvement in cycle life has been achieved, moving the technology closer to practical applications.