Physical investigations on pure and KBr doped poly(vinyl alcohol) (PVA) polymer electrolyte films for solid state battery applications

Potassium ion conducting polymer electrolyte films were prepared based on poly(vinyl alcohol) (PVA) complexed with 5, 10 and 15 wt% potassium bromide (KBr) salt using solution-casting technique. X-ray diffraction and Fourier transform infrared spectroscopy studies were used to determine the complexation of the KBr salt with polymer structure. Differential scanning calorimetry was used to determine the melting temperatures and relative crystallinity values of pure PVA and PVA:KBr complexed films. The conductivity of the polymer films was measured using impedance spectroscopy. Room temperature ionic conductivity was found to be a maximum (1.23 × 10−5 S cm−1) for the (PVA:KBr) (85:15) complexed film, whose K+ ion transport number was found to be 0.97. Electrochemical cells were fabricated in the configuration K/(PVA:KBr)/(I2 + C + Electrolyte) and their discharge characteristics were studied under a constant load of 100 kΩ.