Status and Challenges of Solid-State Electrolytes for Potassium Batteries.

Potassium solid-state batteries (K-SSBs), utilizing solid-state K-ion electrolytes (K-SSEs) and potassium metal anodes, are promising candidates for large-scale energy storage due to their low cost, safety, and high energy density. The limited availability of K-SSEs with excellent electrochemical performances and the associated interfacial issues are the primary hurdles in advancing K-SSBs. In this review, the ion conduction mechanism and the key parameters of solid electrolytes are re-examined, and then reviewed typical inorganic and polymer electrolytes for K-ion migration, highlighting the critical role of electrolyte crystal structure, composition, and preparation techniques in achieving optimal ionic conductivity and stability. This study further emphasizes the essential role of strategic interface engineering, including the formation of stable solid-electrolyte interphases at the anode and the construction of efficient K⁺-ion transport channels at the cathode, on mitigating interfacial impedance and enabling stable cycling performance of K-SSBs. Finally, promising research directions are proposed to advance the development of high-performance K-SSEs, anticipating to provide some inspiration and reference for the continued advancement of K-SSBs.