Poly (1-vinylpyrrolidone-co-vinyl acetate) (PVP-co-VAc) based gel polymer electrolytes for electric double layer capacitors (EDLC)

The present work describes the electrochemical performance of gel polymer electrolytes containing two different sodium salts such as sodium trifluoromethanesulfonimide (NaTFSI) and sodium trifluoromethanesulfonate (NaOTF)). Poly (1-vinylpyrrolidone-co-vinyl acetate) P(VP-co-VAc) and the mixture of ethylene carbonate and propylene carbonate (EC: PC) have been employed as the host polymer and plasticizer, respectively. Through electrochemical impedance spectroscopy study, the GPE system containing 50% of NaTFSI (System 1: A5) has achieved higher ionic conductivity (1.79 x 10(-3) S cm(-1)) compared to the GPE system containing 50% of NaOTF (1.21 x 10(-3) S cm(-1)) (System 2: B5). The higher ionic conductivity of System 1: A5 was owing to the larger ionic radius of (TFSI-) anion. Temperature dependent studies affirmed that the ionic conductivity of all samples obeyed Arrhenius behavior. Fourier transform infrared spectroscopy revealed the formation of complex within the GPE systems which indicates the good interaction between the host polymer and the salts. X-ray diffraction analysis demonstrated the reduction in crystallinity of System 1: A5 is greater than that of System 2: B5. The maximum specific capacitance achieved by the EDLC employing System 1: A5 and System 2: B5 was 13.44 F/g (67% capacitance retention) and 13.33 F/g (4.2% capacitance retention), respectively.