Investigating the structural, optical, and thermal behavior of CuCl2 incorporated PVP/glycerin-based polymer electrolytes for energy storage applications

Abstract

Polymer electrolyte films composed of PVP and PVP/glycerin with varying concentrations of CuCl₂ (10, 20, and 30 wt.%) were synthesized using the solution casting method. The synthesized electrolyte films were characterized using FTIR, XRD, UV–Vis, DSC, and TGA techniques. FTIR spectroscopy revealed an O–H stretching vibration of PVP around 3300 cm⁻¹, which experienced broadening and a reduction in intensity upon the introduction of glycerin and CuCl₂. XRD analysis displayed a characteristic peak at 2θ ~ 20°, with the peak shifting towards higher angles and a slight decrease in intensity as the CuCl₂ concentration increased, indicating a disruption of the crystalline structure of the host matrix. UV–Vis analysis revealed that the optical bandgap of pure PVP was 3.6 eV, whereas the incorporation of 10, 20, and 30 wt.% CuCl₂ into the PVP/glycerin system resulted in a significant reduction of the bandgap to 2.4, 1.7, and 1.4 eV, respectively. DSC measurements indicated a decrease in the glass transition temperature (T_g) from 150 °C for pure PVP to 146, 144, and 140 °C for the PVP/glycerin composites containing 10, 20, and 30% CuCl₂, respectively. TGA results indicated enhanced thermal stability for PVP/glycerin with CuCl₂, which remained stable up to 225 °C, compared to pure PVP. According to conductivity measurements, the highest ionic conductivity achieved for a system containing 20 wt.% CuCl₂ is 6.47 × 10⁻⁴ S/cm at room temperature. The experimental data suggest that these optimized electrolyte materials could be suitable candidates for high-performance energy storage technologies.