High-performance solid state supercapacitors based on intrinsically conducting polyaniline/MWCNTs composite electrodes

The electrochemical behavior of the prepared solid state supercapacitors based on the composites of polyaniline (PANI) with multiwalled carbon nanotubes (MWCNTs) have been reported in this study. The PANI/MWCNTs composites are prepared by simple chemical oxidation polymerization method with different doping concentrations (2, 4, 6 and 8 wt%) of MWCNTs. X-ray diffraction studies performed on the pristine and composite samples reveal the semi-crystalline nature of PANI, with three well visualized reflections at 2 theta values of 16, 22 and 25(o), corresponding to the hkl planes (011), (020) and (200) respectively, of PANI. The absence of crystalline peaks of MWCNTs in the composites reveal the complete wrapping of PANI chains over the MWCNTs. Field emission scanning electron microscopy studies reveal the agglomerated structural form of the prepared samples. Raman spectroscopic studies confirm the growth of PANI and its composites with MWCNTs, consisting of all the characteristic bands of PANI. The electrochemical activity of the prepared supercapacitor is recorded through cyclic voltammetry. The prepared supercapacitor with 8 wt% doping concentration of MWCNTs, has significantly high values of 446.89 F/g, 248.29 Wh/kg and 16,865.12 W/kg for the specific capacitance, energy density and power density, respectively. The high values of these parameters for the supercapacitor with 8 wt% doping concentration of MWCNTs can be attributed to the high electrical conductivity, low internal resistance and inherent porous nature of MWCNTs. The PANI-MWCNTs composites have more stability with capacitance retention of 83.97% for PANI/MWCNTs composite (8 wt%), whereas, pristine PANI exhibits only 64.12% of the original capacitance after 10,000 cycles and the stability increases with the increase in doping concentration of MWCNTs.