1-butyl-3-methylimidazolium chloride based polymer electrolytes for supercapacitor applications

The aim of this work was to investigate the effect of 1-butyl-3-methylimidazolium chloride (BMIMCI) on the structural, electrical, and electrochemical properties of PVDF-HFP/NaI solid polymer electrolyte for supercapacitor applications. In this work, solid polymer electrolyte films were prepared using the solution casting method with Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) as the host polymer. Sodium iodide salt (NaI) and an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCI) was incorporated in different weight percentages to improve ionic conductivity. The maximum conductivity of 8.07 × 10 − 4 S/cm was achieved at 4% BMIMCI. The ionic transference number (t ion ) was found to be 0.92, indicates that the ions mainly take part in the conduction process. Linear sweep voltammetry (LSV) revealed a wide electrochemical stability window of 3.67 V, making the electrolyte suitable for practical applications. Surface morphology of the films was studied using scanning electron microscopy (SEM) and Polarized Optical Microscopy (POM), which showed a more uniform and less crystalline structure after the addition of the ionic liquid, supporting enhanced ion movement. Differential scanning calorimetry study showed a decrease in crystallinity and an increase in amorphous nature, helping easier movement if ions inside the polymer electrolyte. The optimized solid polymer electrolyte films was further used to fabricate a supercapacitor device. The device exhibited a specific capacitance of 26.3 F/g. Galvanostatic charge-discharge analysis gave a maximum specific capacitance of 10.1Fg − 1 , a coulombic efficiency of 98%, an energy density of 3.9 Whkg − 1 , and a power density of 2650 Wkg − 1 . The device retained about 95% of its initial specific capacitance after 1000 charge-discharge cycles, indicating good cycling stability, showing good electrochemical performance.