Enhanced electrochemical stability of all-polymer redox supercapacitors with modified polypyrrole electrodes

Redox supercapacitors are attracting increasing attention as high power electrochemical sources and can either be coupled with batteries to provide peak power or replace batteries for memory back-up. In the present work, all-polymer solid-state supercapacitors with LiClO4 and LiCF3SO3 doped polypyrrole electrodes and P(VDF-HFP)-PMMA based polymer gel electrolyte are fabricated. The polypyrrole electrodes are irradiated with 160MeV Ni12+ ions at 5 x 10(10), 5 x 10(11) and 5 x 10(12) ions cm(-2). A comparative study is made between unirradiated and irradiated supercapacitors with polypyrrole-based electrodes. Am average capacitance of about 200 F gm(-1) is obtained. On successive charging and discharging, the capacitance decreases for supercapacitors with unirradiated electrodes but remains stable when irradiated electrodes are used. In addition, the capacitance is slightly decreased compared with that for unirradiated electrodes. Charge-discharge studies show a decrease in total charge-discharge time for supercapacitors with irradiated electrodes. The capacitance values calculated from cyclic voltammograms are higher than those determined from charge-discharge plots due to the added contribution of a leakage current. The coulombic efficiency of all the supercapacitors is about 90%. (c) 2006 Elsevier B.V. All rights reserved.