Poly(vinylidene fluoride-co-hexafluoropropylene) based in-situ silica composite polymer gel electrolyte for wide-temperature-range supercapacitor applications

초록

Solid-state electrochemical devices with high energy density and enhanced safety were in growing demand for sustainable energy storage. Electrolytes played a vital role in device safety and stable operating voltage. Here, a flexible, free-standing poly(vinylidene fluoride-hexafluoropropylene) (PVdF-co-HFP)-based composite polymer electrolyte (CPE) operating over a wide potential window (2.5 V) was fabricated via phase inversion. The effects of ceramic nanofillers such as silica (SiO2), bismuth oxide (Bi2O3), and zinc oxide (ZnO) on crystallinity, morphology, and electrochemical behavior were investigated. Among them, the in-situ silica-incorporated CPE (CPE-S) exhibited superior performance, showing high porosity (85%), ionic conductivity (0.520 mS cm(-1)), electrolyte uptake (303%), and retention (0.81). A flexible supercapacitor assembled using CPE-S and graphite-coated paper delivered a specific capacitance of 5.13 F g(-1) and an energy density of 4.67 Wh kg(-1) at 2 mV s(-1), retaining 72% capacitance and similar to 99% Coulombic efficiency over 10,000 cycles. The device demonstrated excellent thermal stability at 10, 30, and 80 degrees C and mechanical flexibility, maintaining comparable capacitance before and after bending (12.36 and 12.84 mF g(-1)). These results confirmed the suitability of PVdF-co-HFP-based CPEs for high-temperature and flexible electric double-layer capacitor applications in extreme operating environments.

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