Copolymer hydrogel as self-standing electrode for high performance all-hydrogel-state supercapacitor

Herein, a conducting copolymer hydrogel of poly(aniline-co-pyrrole)/polyvinyl alcohol (PACP/PVA) was prepared by in-situ polymerization of aniline and pyrrole in aqueous solution of phytic acid and PVA. This PACP/PVA hydrogel can be used directly as self-standing electrode for supercapacitors. The hydrogel electrode delivers high electrochemical capacitance (633.5 F g−1 at 0.5 A g−1, 1267 mF cm−2 at 1 mA cm−2) and excellent cycling stability (86.4% capacitance retention after 10,000 cycles). In particular, the remarkable flexibility of the PACP/PVA hydrogel electrode is demonstrated by 81.7% of initial capacitance retention after repeated bending 500 cycles. Based on PACP/PVA hydrogel electrode and a typical PVA/H2SO4 hydrogel electrolyte, an all-hydrogel-state supercapacitor was assembled. The supercapacitor demonstrates high areal capacitance of 317 mF cm−2 at 1 mA cm−2 and energy density of 44 µWh cm−2 (22 Wh kg−1) at 250 µW cm−2 (125 W kg−1). This work provides a new direction for fabricating self-standing flexible hydrogel electrode materials for smart and wearable devices.