Dielectric relaxation and transport properties of LiBr-doped PVA/MC electrolytes for energy storage application

In this study, effect of lithium bromide (LiBr) doping on the structural, thermal, electrical, and transport properties of poly(vinyl alcohol) (PVA)/methyl cellulose (MC) polymer blend electrolytes was systematically investigated. FTIR results revealed that incorporation of LiBr into the polymer blend matrix resulted in interactions between Li+ ions and the polar functional groups of the polymer, leading to complexation. This disrupted the crystalline domains, increased the amorphous content, and enhanced segmental motion of the polymer chains as observed in XRD results. Thermal analysis confirmed increased stability of the doped electrolytes. Dielectric studies revealed an increase in the dielectric parameters with LiBr concentration and exhibited non-Debye relaxation behavior, indicative of localized ionic motion. AC conductivity followed Jonscher's universal power law, while temperature-dependent conductivity was consistent with the correlated barrier hopping model, confirming thermally activated ion hopping as the dominant conduction mechanism. Impedance spectroscopy and transference number measurements (t₊ = 0.98) established that conduction is primarily ionic, with Li+ ions as the dominant charge carriers. The results demonstrate that LiBr-doped PVA/MC polymer blend electrolytes exhibit enhanced ionic conductivity, thermal stability, and single-ion transport, highlighting their potential for application in energy storage devices.