Solvation Structure Regulation Enables 4.5 V High-Voltage Ether-Based Electrolytes for Stable Potassium-Ion Storage

Ether-based electrolytes have attracted considerable interest in the development of potassium-ion batteries (PIBs) owing to their superior compatibility with potassium metal anodes. Nevertheless, their inherently limited electrochemical stability windows, particularly with respect to inadequate oxidative stability, pose significant challenges for the practical implementation of high-voltage cathodes exceeding 4 V. Traditional ether electrolytes tend to undergo rapid decomposition at elevated potentials, leading to the deterioration of the cathode-electrolyte interphase and severe capacity degradation. In this study, we present a solvation chemistry engineering approach by incorporating Bis(2-fluoroethyl) carbonate (BFC) into a 1,3-dioxane electrolyte. The addition of BFC modifies the solvation sheath structure, enhances the desolvation kinetics of potassium ions (K + ), and simultaneously broadens the electrochemical stability window. As a result, the optimized electrolyte facilitates stable cycling of high-voltage cathodes operating at approximately 4.5 V in PIBs, achieving a remarkable capacity retention of 92.2% after 1800 cycles under high current densities, alongside an outstanding Coulombic efficiency of 99.95%. This work establishes a framework for the deliberate manipulation of solvation chemistry in the design of high-voltage electrolytes and provides a viable strategy to overcome the voltage limitations inherent to ether-based electrolyte systems.