Supercapacitors (SCs), also referred to as ultracapacitors or
electrochemical capacitors, are typically regarded as a suitable choice to store energy by transforming chemical energy into electrical
energy because of their high power density, long life cycle,
good reversibility, environmental friendliness and safety [1e4].
According to the energy storage mechanism, the faradic pseudocapacitance
is carried out by fast redox reactions or phase changes
on the surface or subsurface of electrodes offering much higher
energy densities than electrical double-layer capacitor (EDLC) [5,6].
Therefore, many research works focus on the design, preparation
and capacitive property of the multicomponent electrode materials
combining energy storage of electrostatic attraction and faradic
reaction, in which active materials such as metal oxides or conducting
polymers can enhance the capacitance remarkably, while
the carbon-based material as a support can not only increase the
effective utilization of active materials, but also improve the electrical
conductivity and mechanical strength of the composite
electrodes