Cyclic Ether‐Based Electrolyte with a Weak Solvation Structure for Advanced Potassium Metal Batteries

Abstract Potassium metal batteries (PMBs) are promising candidates for large‐scale energy storage. Conventional carbonate electrolytes exhibit unsatisfactory thermodynamic stability against potassium (K) metal anode. Linear ether is widely adopted because of its compatibility with K metal, but the poor oxidation stability restricts the application with high‐voltage cathodes. Herein, a weakly solvating cyclic ether is proposed as a solvent to stabilize the K‐electrolyte interface and build a robust solid‐electrolyte interphase (SEI). This weakly solvating electrolyte (WSE) possesses an anion‐dominated solvation structure, which facilitates the anion decomposition for constructing an inorganic‐rich SEI. The superior mechanical properties of the SEI, as examined by atomic force microscopy, prevent the SEI from fracture. Consequently, this WSE achieves highly reversible plating/stripping behavior of K metal for 1300 h with a high average Coulombic efficiency of 99.20%. Stable full cells are also demonstrated with a high‐voltage cathode at harsh conditions. This work complements the design of WSEs for advanced PMBs by cyclic ether solvents.