Spectroscopic studies on ion dynamics of PVP-NH4SCN polymer electrolytes

Proton-conducting polymer electrolyte comprising of poly(N-vinyl pyrrolidone) (PVP) and ammonium thiocyanate (NH4SCN) are prepared by solvent casting method with different polymer-salt concentrations. The changes in the Raman spectra with increasing NH4SCN concentration state that the free ion concentration is maximum for 20 mol% NH4SCN concentrated system. At higher salt concentrations (25 mol%), the effective number of charge carriers decreases due to the formation of ion aggregates as confirmed by the Raman analysis. Solid-state NMR and MAS NMR studies are performed to obtain the information about the ionic structure, mobility of the charge carriers, and also to gain insight into the polymer-salt interactions in the polymer electrolytes. The results of ionic transference number show that the charge transport in these polymer electrolytes is mainly due to ions.