Liquid electrolyte mediated flexible pouch-type hybrid supercapacitor based on binderless core–shell nanostructures assembled with honeycomb-like porous carbon

Abstract

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.