Cross-Linked Polymer Hydrogel Electrolytes for Electrochemical Capacitors

Acidic polyvinyl alcohol/polyacrylic acid blend hydrogel electrolytes �BHEs� were prepared by cross-linking with glutaraldehyde \nand perchloric acid. These acidic BHEs were treated suitably to realize alkaline and neutral BHEs. Amorphicity of BHEs was \nfollowed by differential scanning calorimetry. Ionic conduction in acidic BHEs was found to take place by a Grötthus-type \nmechanism whereas in alkaline and neutral BHEs it was due to a segmental motion mechanism. Ionic conductivity of BHEs was \nfound to range between 10−3 and 10−2 S cm−1. Electrochemical capacitors assembled with acidic polyvinyl alcohol hydrogel \nelectrolyte yielded a maximum capacitance of �60 and 1000 F g−1 with BP carbon and RuOx·xH2O/C electrodes, respectively.