Effect of lithium bromide doping on structural, dielectric, and transport properties of methylcellulose-based solid polymer electrolyte films

The study focuses on the preparation and characterization of solid polymer electrolyte films using methylcellulose (MC) and lithium bromide (LiBr) at various concentrations (5–25wt%). The films were prepared by the solution casting method, and their microstructural, thermal, dielectric, and transport properties were analyzed. Fourier transform infrared and X-ray diffraction results confirmed the complexation between the dopant and polymer and showed an increase in the amorphous phase of the polymer with doping. Thermogravimetric analysis showed an increase in the thermal stability of the polymer. Dielectric studies revealed that the dielectric parameters exhibited non-Debye behavior similar to polar dielectric materials. The highest ionic conductivity of 6.04 × 10^–3 S/cm was observed for the 25wt% LiBr-doped electrolyte at room temperature. The study also determined the ion transport number in the 25wt% doped electrolyte and carried out a transient ionic current study to confirm the contribution of the number of ionic species to major conduction within the electrolyte. Overall, the study highlights the potential of MC–LiBr solid polymer electrolytes for use in electrochemical devices.