Nonfluorinated Antisolvents for Ultrastable Potassium-Ion Batteries

A robust interface between the electrode and electrolyte is essential for the long-term cyclability of potassium-ion batteries (PIBs). An effective strategy for achieving this objective is to enhance the formation of an anion-derived, robust, and stable solid-electrolyte interphase (SEI) via electrolyte structure engineering. Herein, inspired by the application of antisolvents in recrystallization, we propose a nonfluorinated antisolvent strategy to optimize the electrolyte solvation structure. In contrast to the conventional localized superconcentrated electrolyte introducing high-fluorinated ether solvent, the anion-cation interaction is considerably enhanced by introducing a certain amount of nonfluorinated antisolvent into a phosphate-based electrolyte, thereby promoting the formation of a thin and stable SEI to ensure excellent cycling performance of PIBs. Consequently, the nonfluorinated antisolvent electrolyte exhibits superior stability in the K||graphite cell (negligible capacity degradation after 1000 cycles) and long-term cycling in the K||K symmetric cell (>2200 h), as well as considerably improved oxidation stability. This study demonstrates the feasibility of optimized electrolyte engineering with a nonfluorinated antisolvent, providing an approach to realizing superior electrochemical energy storage systems in PIBs.