Optimization of the Electrochemical Performance of a Composite Polymer Electrolyte Based on PVA-K₂CO₃-SiO₂ Composite

Composite polymer electrolyte (CPE) based on polyvinyl alcohol (PVA) polymer, potassium carbonate (K₂CO₃) salt, and silica (SiO₂) filler was investigated and optimized in this study for improved ionic conductivity and potential window for use in electrochemical devices. Various quantities of SiO₂ in wt.% were incorporated into PVA-K₂CO₃ complex to prepare the CPEs. To study the effect of SiO₂ on PVA-K₂CO₃ composites, the developed electrolytes were characterized for their chemical structure (FTIR), morphology (FESEM), thermal stabilities (TGA), glass transition temperature (differential scanning calorimetry (DSC)), ionic conductivity using electrochemical impedance spectroscopy (EIS), and potential window using linear sweep voltammetry (LSV). Physicochemical characterization results based on thermal and structural analysis indicated that the addition of SiO₂ enhanced the amorphous region of the PVA-K₂CO₃ composites which enhanced the dissociation of the K₂CO₃ salt into K⁺ and CO₃^2- and thus resulting in an increase of the ionic conduction of the electrolyte. An optimum ionic conductivity of 3.25 × 10^-4 and 7.86 × 10^-3 mScm^-1 at ambient temperature and at 373.15 K, respectively, at a potential window of 3.35 V was observed at a composition of 15 wt.% SiO₂. From FESEM micrographs, the white granules and aggregate seen on the surface of the samples confirm that SiO₂ particles have been successfully dispersed into the PVA-K₂CO₃ matrix. The observed ionic conductivity increased linearly with increase in temperature confirming the electrolyte as temperature-dependent. Based on the observed performance, it can be concluded that the CPEs based on PVA-K₂CO₃-SiO₂ composites could serve as promising candidate for portable and flexible next generation energy storage devices.