Fabrication of flexible conducting UiO-66/phytagel/NaCl/glycerol composite sheets and their performance as electrolytes for supercapacitor applications

Abstract

The energy density of solid polymer electrolytes (SPEs) is limited by low ionic conductivity caused by interfacial resistance at the electrode-electrolyte interface. To address this issue, composite solid polymer electrolytes (CSPEs) were developed by incorporating UiO-66 (metal-organic framework), phytagel, NaCl and glycerol. FTIR analysis confirms the absence of any new chemical bonding, indicating the formation of ideal CSPE. PXRD analysis showed reduced crystallinity upon blending UiO-66/phytagel and glycerol. Morphological analysis via FESEM shows the homogeneity of the composite material. Electrochemical Impedance Spectroscopy (EIS) revealed a stepwise reduction in bulk resistance with the successive addition of UiO-66, NaCl and glycerol, leading to the final CSPE, which exhibited the highest ionic conductivity of 1.00 × 10⁻⁰³ S cm⁻¹ with synergistic dielectric properties. The electrochemical stability window of the CSPE was reported from −0.8 V to +2.3 V. Cyclic voltammetry (CV) demonstrated a specific capacitance of 144 F g⁻¹ at 1 mV s⁻¹ and 12 F g⁻¹ at 100 mV s⁻¹. Coulombic efficiency remained ∼95 % and ∼ 99 % at 0.1 and 0.05 A g⁻¹ up to 1000 cycles during galvanostatic charge-discharge (GCD) analysis, showing the long-term capability of charge-discharge in the device. These findings highlight the material's potential for next-generation energy storage applications.