Asymmetric supercapacitor containing poly(3-methyl thiophene)-multiwalled carbon nanotubes nanocomposites and activated carbon

Poly(3-methyl thiophene) (PMT) and multiwalled carbon nanotubes (MWCNT) based nanocomposites have been prepared chemically at various wt. ratios. Nanocomposites are characterized by TEM, TGA, XRD and Raman spectroscopy. The morphology of nanocomposites shows fine wrapping of PMT over MWCNT. Electrodes containing PMT nanocomposites have been prepared and p-doping of nanocomposites studied in electrolyte containing 1 M tetraethylene ammonium tetra fluroborate in propylene carbonate. Specific capacitance of the nanocomposites increases with increase in PMT loading and a maximum specific capacitance of 296 F g(-1) has been obtained for the nanocomposite with PMT/MWCNT wt. ratio of 87.5/12.5. Non aqueous based asymmetric supercapacitors containing PMT nanocomposites as the positive electrode and activated carbon (AC) as the negative electrode have been fabricated. Supercapacitor unit cells have been constructed at the optimized mass ratio of the electrodes so as to obtain maximum total specific capacitance and specific energy. Highest specific capacitance obtained for PMT nanocomposite-AC system is 38.5 F g(-1) of the total active material in the supercapacitor. The complex capacitance of the supercapacitors derived from electrochemical impedance spectroscopy reveals that supercapacitor containing nanocomposites with higher concentration of MWCNT has shorter relaxation time constant (to) leading to higher rate capability. Continuous charge-discharge cycling studies indicate that PMT nanocomposite-AC supercapacitor have better stability than bulk PMT-AC supercapacitor. (C) 2013 Elsevier Ltd. All rights reserved