Enhancing interest of portable/flexible electronics postulated
for the clean and sustainable energy storage device such as flexible
solid state supercapacitor (FSS-SCs), which can not only store
energy efficiently and safely, but also possess additional features
such as the high mechanical integrity, longer cycling life and high
power capability [1–3]. Firstly, these prospects give direction, but
created new challenges regarding safety, high voltage applications,
and long-term stability of FSS-SCs devices. Therefore, the broad
research efforts are continuing electrolyte, cathode and anode
material to boost the electrochemical performance of FSS-SCs [4].
Despite the significant progress that has been made in developing
the efficient cathode and anode electrode materials, while electrolytes are relatively less explored. Traditionally, the liquid and
solid electrolytes are explored in supercapacitor devices due to
their own unique properties, which are mainly depend upon their
state of matter. The liquid electrolytes have been commonly used
as electrolyte to fabricate the supercapacitor device. As it’s low
cost, high ionic conductivity and easy synthesis, but it has high risk
of leakage and can cause the corrosion of metallic electrodes [5].
On the other side, solid electrolytes are also employed as electrolyte to develop the supercapacitor device, as it has no problem
for corrosion of metallic electrodes, but low ionic conductivity
and poor interfacial properties of solid electrolyte limiting their
usefulness in supercapacitor device [6,7]. Hence, there is an emergent need to find the alternative/or new state of electrolyte which
is in between a liquid and a solid, and has a combination of liquid
and solid components to get desired electrochemical features.