Executive Summary : | The whole research focus on supercapacitors (SCs) is to enhance their energy density (E) to the order
of Li-ion batteries without losing their high power density (P). An evident choice to progress ahead with
such focus would be the utilization of asymmetric/hybrid SCs, as they can be made to furnish vital
energy storage properties like large potential window, specific capacitance (Cs), E, P, coulombic
efficiency (ƞ), rate capability and cyclic stability, in higher magnitudes by using the harmless aqueous
electrolytes. Among the existing electrode materials, the metal oxides (MOs) and conducting polymers
(CPs), particularly, polyaniline (PANI) and polypyrrole (PPy), are with extraordinary qualities to be used
as electrode materials, but each of them suffers from some serious limitations, which reduce their
energy storing properties. The main limitations of PANI and PPy are their low order cyclic stability and
rate capability. The merits of PANI and PPy are their ability to furnish E and P in higher magnitudes.
The energy storing ability of these CPs can be further enhanced by utilizing their faradic chemistry and
variable electrical conductivity. In addition, the PANI and PPy are facile to synthesis, inexpensive, less
toxic, eco-friendly and exhibit high theoretical Cs (PANI - 2000 F g-1 and PPy - 3400 F g-1). However,
another notable limitation of PPy, is that the disparity between its theoretical and experimental Cs is
remarkable large, which still creates the substantial research gap to explore the PPy further. The MOs
are good providers of high E and rate capability (merits) but provide low P and cyclic stability
(limitations). Therefore, it is a rational notion to add these MOs to the integrity of PANI and PPy to
produce efficient electrode materials for SCs (by synergistic effect). Thus, each of these aforementioned
different faradic materials possess their intrinsic merits and limitations. The merits of the
aforementioned materials make the material suitable for the further study, when their limitations are
subside. Hence, it is a novel notion to make supercapacitive materials by integrating all the merits of
them. Among different MOs available, the MnO2, V2O₅ and SnO2, are remarkable as they are with, high
theoretical Cs of 3700, 2210 and 2134 F g-1 at 1.2 V respectively, multiple oxidation states, cheap and
facile to synthesis. The integrity of the composite electrode is also believed to substantially deter the
electrode material from undergoing structural failures and there by imparting overall stability to the
device, which is expected to surpass the limitations of conventional capacitors and replace the Li-ion
batteries with high E. And this replacement is the aim of the project. Hence, it is proposed to develop
nanocomposite electrodes, containing PPy, PANI, MnO2, V2O₅ and SnO2 as binary and ternary
composites, which combine the merits and mitigate the shortcomings of the individual components to
create effective supercapacitors. |