Conductivity Study on Proton-Conducting Nanocomposite Plasticized Polymer Electrolytes: A Review

This paper reviews proton-conducting polymer electrolytes comprising different polymers, salts, and acids. The ionic conductivity of plasticized polymer electrolytes has been found to increase with the addition of plasticizers due to the dissociation of ion aggregates or undissociated salt/acid present in the electrolytes, i.e., σ (plasticized polymer electrolytes) > σ (unplasticized polymer electrolytes). Proton-conducting nonaqueous nanocomposite plasticized polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) polymers; different ammonium salts and acids as proton conductors; ethylene carbonate (EC), propylene carbonate (PC), dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl carbonate (DMC), diethyl carbonate (DEC) as plasticizers; fumed silica and alumina as nano-fillers have been discussed in details. Conductivity studies (effect of salt/acid, effect of plasticizers, effect of nano-fillers, and effect of temperature), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) studies for these electrolytes have been discussed and reported in the paper. Nanocomposite plasticized polymer electrolytes showed high ionic conductivity (in the order of 10^-1 to 10^-2 S/cm) at room temperature along with good thermal and mechanical stability due to the simultaneous addition of both plasticizers and nano-fillers. These nanocomposite polymer electrolytes are the best candidates for use in various electrochemical devices like solid-state batteries, fuel cells, supercapacitors, sensors, separators, and other electrochromic devices.