High Conductivity in a Fluorine-Free K-Ion Polymer Electrolyte

Solid polymer electrolytes (SPEs) could play a major role in the transition to safer and high-energy-density potassium-based batteries. However, most polymeric K-ion are based on fluorine-containing anions flammable organic solvents, whose safety is nowadays question. Herein, we report facile solvent-free synthesis of series several poly(ethylene oxide) (PEO)-based SPE solid solutions with KBPh4 salt as potassium-ion source, including formation two crystalline (PEO)n/KBPh4 complexes. The ionic conductivity these novel SPEs above below melting point PEO rationalized light their glass-transition temperature chemical composition. We highlight that PEO, complexes may not be intrinsically ionically conducting, but they act ion sinks preventing cross-linking contact pairs lower leading 1.1 × 10–4 S cm–1 at 55 °C. A high 1.8 10–3 achieved 80 °C for optimum (PEO)30/KBPh4 composition (3.2 mol % KBPh4). Besides, compositions were found stable up 4 V vs K0 metal electrode 60 composite electrolyte employed an all-solid-state symmetric cell Prussian Blue electrodes showed reversible K+-ion (de)intercalation, where capacity 20 mAh g–1 low voltage hysteresis cycles. Considering material availability, ease synthesis, promising electrochemical properties, this work encourage future research fluorine-free