Cross-linked polymer hydrogel electrolytes for electrochemical capacitors

Acidic polyvinyl alcohol/polyacrylic acid blend hydrogel electrolytes (BHEs) were prepared by cross-linking with glutaraldehyde and perchloric acid. These acidic BHEs were treated suitably to realize alkaline and neutral BHEs. Amorphicity of BHEs was followed by differential scanning calorimetry. Ionic conduction in acidic BHEs was found to take place by a Grotthus-type mechanism whereas in alkaline and neutral BHEs it was due to a segmental motion mechanism. Ionic conductivity of BHEs was found to range between 10(-3) and 10(-2) S cm(-1). Electrochemical capacitors assembled with acidic polyvinyl alcohol hydrogel electrolyte yielded a maximum capacitance of similar to 60 and 1000 F g(-1) with BP carbon and RuOx center dot xH(2)O/C electrodes, respectively. (c) 2006 The Electrochemical Society.