Electrical Conductivity of the System Polyvinyl Alcohol–Sodium Thiocyanate

Sodium-ion polymer electrolytes based on polyvinyl alcohol (PVA) and sodium thiocyanate (NaSCN) are studied as the promising energy storage materials. Attention is focused on the effect of the NaSCN concentration on the ionic conductivity, phase transitions, and structural changes in this system in the temperature interval from 293 to 373 K. The results of differential thermal analysis, spectroscopy, and electrochemical impedance spectroscopy show that the system with 20 wt % NaSCN has the considerably higher ionic conductivity. The ion transport is considerably improved due to the break of hydrogen bonds in the polymer matrix and an increase in the amorphous phase fraction in the polymer. Quantum chemical calculations reveal the effect of solvation and hydration on the properties of ions in the system, in particular, the preferential interaction of sodium cations with OH groups in PVA.