Highly flexible solid-state supercapacitor based on graphene/polypyrrole hydrogel

Polymer-based solid-state supercapacitors (PSCs) have potential for large-scale flexible energy storage applications because of their high electrochemical activity and the low cost. However, one of the obstacles to developing PSCs is maintaining the high flexibility (horizontal and vertical) and cycle stability along with a high specific capacitance. Thus, to develop high-flexible PSCs with excellent cycle stability, this paper presents a novel and highly flexible solid-state supercapacitor based on a graphene/polypyrrole hydrogel (PGH) with long cycle performance that was prepared via a simple heating approach. Specifically, the pore structures based on the PGH not only introduce more electrochemically active surfaces for absorption/desorption of electrolyte ions but also provide additional mechanical flexibility. The unique structural design for flexible supercapacitors exhibits a high specific capacitance of 363 F cm−3 at a current density of 1.0 mA cm−3 and excellent cycle stability with a capacitance retention of 98.6% after 12000 charge/discharge cycles under bent, folded and twisted states. The remarkable electrochemical and flexible properties of the PGH developed in this study are higher than those of similar polypyrrole (PPy)-based supercapacitors previously reported.