Polymer electrolyte based solid state redox supercapacitors with poly (3-methyl thiophene) and polypyrrole conducting polymer electrodes

Types I and II solid state redox supercapacitors have been constructed using polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF3SO3 plasticised with poly (ethylene glycol) (PEG). The performance of the capacitors has been characterised by a.c. impedance, linear sweep voltammetry, galvanostatic charge-discharge methods and long term cycling tests. The asymmetric type II capacitors with p-doped pPy and pMeT electrodes give a capacitance value ∼ 2 mF cm−2 (equivalent to 18 Fg−1 of the total mass of the electrodes) and can be charged up to the voltage of 1.7 V. The symmetric type 1 capacitors of the configuration pPy | polymer electrolyte | pPy and pMeT | polymer electrolyte | pMeT show comparable values of capacitance but they are limited to the working voltage of <1.0 V.