New polymer electrolyte poly(acrylonitrile)–sulpholane–(C2H5)4NBF4 for chemical capacitors

A series of ion conducting, thin-film polymer electrolytes, based on poly(acrylonitrile), tetraethylammonium tetrafluoroborate and sulpholane (tetramethylene sulphone, TMS), PAN–(C2H5)4NBF4–TMS, were prepared using the casting technique. The polymer electrolytes were transparent with rubberlike elasticity. Maximum conductivity was at the level of 10 mS/cm at room temperature. The temperature dependence of the conductivity indicates the Arrhenius type of the behaviour, with the activation energy of 12 kJ/mol. The electrochemical stability window of the electrolyte, determined at the glassy carbon electrode, was of ca. 3 V. Capacitor electrodes, in the form of thin foils, were prepared by the casting technique, using activated carbon powder (ACP) mixed with acetylene black (AB) or graphite (G) as an electrode active material. The performance of capacitors, having a coin-like shape, a diameter of 18 mm and a mass of 180–350 mg, was determined by cyclic voltammetry, impedance spectroscopy and galvanostatic charging and discharging.