Ion conduction mechanism in non-aqueous polymer electrolytes based on oxalic acid: Effect of plasticizer and polymer

Abstract

Non-aqueous proton-conducting polymer electrolytes in the film form are synthesized through the complexation of oxalic acid (OA) and polyvinylidenefluoride-co-hexafluoro propylene (PVdF-HFP). Interestingly, the addition of a small amount of the basic component dimethylacetamide (DMA) gives rise to a three-order increase in conductivity. The value is found to depend on the concentrations of the weak acid and DMA in the electrolytes. A maximum conductivity of 0.12 × 10 −3 S cm −1 has been achieved at ambient temperature for electrolytes containing 40 wt.% OA with DMA. The observed increase in conductivity is considered to be due to interactions taking place between the high dielectric polymer media, the acid and the basic plasticizer. These interactions are confirmed from fourier transform infra red (FTIR) studies and supported by differential scanning calorimetry (DSC) measurements. Apart from providing acid–base interaction, the base DMA also improves the surface morphology and reduces the pore volume, both of which help to retain the acid–base complex within the membrane.