Simultaneous Stabilization of Potassium Metal and Superoxide in K–O2 Batteries on the Basis of Electrolyte Reactivity

AbstractIn superoxide batteries based on O2/O2− redox chemistry, identifying an electrolyte to stabilize both the alkali metal and its superoxide remains challenging owing to their reactivity towards the electrolyte components. Bis(fluorosulfonyl)imide (FSI−) has been recognized as a “magic anion” for passivating alkali metals. The KFSI–dimethoxyethane electrolyte passivates the potassium metal anode by cleavage of S−F bonds and the formation of a KF‐rich solid–electrolyte interphase (SEI). However, the KFSI salt is chemically unstable owing to nucleophilic attack by superoxide and/or hydroxide species. On the other hand, potassium bis(trifluorosulfonyl)imide (KTFSI) is stable to KO2, but results in mossy potassium deposits and irreversible plating and stripping. To circumvent this dilemma, we developed an artificial SEI for the metal anode and thus long‐cycle‐life K–O2 batteries. This study will guide the development of stable electrolytes and artificial SEIs for metal–O2 batteries.