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Modification of polymer nanocomposites and significance of ionic liquid 321

11.7.2 Faradaic supercapacitor

These are also called pseudocapacitors and develop quick, convertible redox reactions
to reserve energy, a method that features a lithium-ion battery [32]. Contrasting elec-
tric double-layer supercapacitors, the discharge and charge procedure takes place all
over the electrode, rather than merely on the surface. This grants for superior capac-
itance values, and outcome, relatively advanced energy density. This occurs at the cost
of the lesser energy density than electric double-layer capacitors as the faradaic redox
reactions happen more gently in comparison with electrostatic process [33].

11.8 Role of electrodes in supercapacitors

Electrodes are mainly known as the major element of supercapacitors, as the electric
properties of supercapacitors are greatly depended on the electrode material and
construction.

11.8.1 Transition metal oxides

It is considered to be the famous electrode materials for supercapacitors as they can
acquire higher capacitance values since the method they accumulate charge. These
metal oxides do not just accumulate electrostatic charge on the electrode, although
they too go through rapid redox reactions on the electrode material so as to get an
additional charge. Transition metal oxides show a variety of oxidation states at diverse
potentials and also acquire crystalline structures that permit high conductivity that
implement charges to transmit inside their lattice. The majority of important metal
oxides used as electrode material are as follows: RuO 2 , MnO 2 , PbO 2 , NiO X ,V 2 O 5 ,
and Fe 3 O [34].

11.8.2 Conducting polymers

Conducting polymers are said to be the more feasible substance for supercapacitor
electrodes. They are cheap in cost and have less impact on the atmosphere as com-
pared with transition metal oxides [35]. They are composed of a high-voltage window,
high storage capacity, and high conductivity [35]. These polymers attain capacitance
by means of highly reversible redox reactions. Reduction and oxidation reactions are
the reasons for ions to exit and enter the backbone of the polymers. This appears dur-
ing the whole electrode instead of only on the surface; therefore, higher specific
capacitance values can be obtained [36]. The important conducting polymer elec-
trodes are created with polypyrrole, polyaniline, and polythiophene variants [37].

11.8.2.1 Polyaniline
It is one of the major conducting polymer that has often been used as a low-cost pos-
itive electrode material for electrochemical supercapacitor function because of its
excellent doping-dedoping characteristic and inconsistent oxidation state, which