Liquid electrolyte mediated flexible pouch-type hybrid supercapacitor based on binderless core–shell nanostructures assembled with honeycomb-like porous carbon†
The current challenges in the usage of liquid electrolyte in energy storage devices are closely correlated with the flexibility and portability of the devices. In this paper, a highly flexible, pouch-type hybrid supercapacitor in liquid electrolyte based on a binderless cobalt hydroxide–cobalt molybdate (CoMoO4@Co(OH)2) core–shell structure (prepared by electrochemical deposition; ECD) sandwiched with honeycomb-like porous carbon derived from laboratory waste tissue paper (prepared by a hydrothermal reaction and carbonization) is presented. Its excellent hierarchical core–shell structure and honeycomb-like porous carbon results in a large electrochemically active surface area, which yields a high areal capacity of 265 μA h cm−2 and excellent specific capacitance of 227 F g−1 in liquid potassium hydroxide (KOH) electrolyte with excellent cyclic stability. An assembled pouch-type hybrid supercapacitor using the prepared core–shell structure as the positive electrode and porous carbon as the negative electrode shows an extended working voltage of 1.5 V in 2 M KOH electrolyte, which stores a maximum energy density of 167.5 μW h cm−2. Interestingly, the fabricated pouch-type supercapacitor shows an excellent flexibility under different bending conditions and exhibits remarkable cyclic stability with >98% capacitance retention even after long cycles. Furthermore, the capability of the device is demonstrated by integrating it with a solar cell to drive the various types of light-emitting diodes (LEDs) and seven segment displays for self-powered applications.