Fluorinated Poly(Glycidyl Methacrylate)–Based Gel Polymer Electrolytes With Controlled Crosslinking for Potassium‐Ion Batteries

ABSTRACT Developing gel polymer electrolytes (GPEs) that simultaneously achieve high ionic conductivity, mechanical robustness, and stable electrode interfaces remains a major challenge for potassium‐ion batteries (KIBs). A poly(glycidyl methacrylate) (PGMA)–based GPE was engineered herein through controlled crosslinking with acrylated epoxidized soybean oil (AESO) and subsequent fluorination using trifluoroacetic anhydride (TFAA) to regulate interfacial chemistry and mechanical integrity by facilitating segmental mobility for ion transfer. Electrochemical impedance spectroscopy (EIS) revealed a strong dependence of ion transport on crosslinking density, with an intermediate crosslinking degree providing the optimal balance between structural integrity and chain mobility and yielding an ionic conductivity of 2.9 × 10 −3 Scm −1 at 25°C. Although TFAA modification reduced the ionic conductivity, it substantially enhanced structural stability and electrolyte–electrode compatibility. Linear sweep voltammetry (LSV) demonstrated wide electrochemical stability windows exceeding 4 V for all samples and surpassing 6 V for the optimized compositions. In Prussian Blue|GPE|graphite cells, the optimum electrolyte delivered an initial discharge capacity of ~200 mAh g −1 at 15 mA g −1 with good reversibility, while fluorinated electrolytes exhibited superior interfacial stability in potassium plating/stripping tests. These findings demonstrate that the complementary effects of crosslinking and fluorination can be exploited to balance ion transport and interfacial stability in KIB electrolytes.