Electrolytes and Interphases in Potassium Ion Batteries

Potassium ion batteries (PIBs) are recognized as one promising candidate for future energy storage devices due to their merits of cost‐effectiveness, high‐voltage, and high‐power operation. Many efforts have been devoted to the development of electrode materials and the progress has been well summarized in recent review papers. However, in addition to electrode materials, electrolytes also play a key role in determining the cell performance. Here, the research progress of electrolytes in PIBs is summarized, including organic liquid electrolytes, ionic liquid electrolytes, solid‐state electrolytes and aqueous electrolytes, and the engineering of the electrode/electrolyte interfaces is also thoroughly discussed. This Progress Report provides a comprehensive guidance on the design of electrolyte systems for development of high performance PIBs. Electrolytes play a critical role in the electrochemical performance of emerging potassium‐ion batteries (PIBs). The research progress on electrolytes of PIBs is summarized in terms of fundamental properties, optimization of electrolyte components and engineering of electrode/electrolyte interfaces, providing a comprehensive guidance on designing more suitable electrolytes for high‐performance PIBs.