A Compact‐Solvation Electrolyte Under Low Concentration for High‐Energy Density and Stable Potassium‐Ion Batteries

Abstract The development of potassium‐ion batteries (PIBs) faces significant challenges due to the lack of suitable electrolytes to achieve satisfactory energy density and long‐term stability. This work reports an innovative compact‐solvation electrolyte (CSE) strategy leveraging ionic liquid‐induced manipulation of solvation structures under low concentration for high‐performance PIBs. The CSE, formulated with a low‐salt concentration of 0.8 M, simultaneously exhibits compact solvation structures with abundant F‐rich anions, high‐ionic conductivity, and low‐desolvation energy. These features lead to enhanced K‐storage thermodynamics and kinetics through the formation of a robust KF‐rich solid electrolyte interphase (SEI) as well as accelerated K + transport kinetics. Consequently, the graphite electrode in CSE delivers a high‐reversible capacity of 252 mAh g −1 with an average Coulombic efficiency of 99.5% after 300 cycles at 50 mA g. Furthermore, the designed CSE enables the Prussian blue||graphite full cell to operate for over 1450 cycles at 50 mA g −1 , maintaining an impressive capacity retention of 88%. This work represents a significant advance in the development of safe and compatible electrolytes for advanced PIBs.