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/H 2 SO 4 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. Graphical abstract