Polyaniline electropolymerized within template of vertically ordered polyvinyl alcohol as electrodes of flexible supercapacitors with long cycle life

Abstract

Recently, polyaniline@polyvinyl alcohol (PANI@PVA) composite materials are favored by many researchers due to the synergistic properties of conductive PANI and flexible PVA. Although PANI@PVA composite materials have been studied widely as electrodes for flexible supercapacitors, it is still a challenge to prepared PANI@PVA hydrogel electrodes with long cycle life. In this work, vertically ordered PANI@PVA hydrogel electrodes with an excellent stability were fabricated via electropolymerizing PANI within a template of vertically ordered PVA hydrogel for the first time. In brief, vertically ordered PVA hydrogel coating on a graphite paper collector was prepared through a repeated freezing-thawing method. Then PANI grew within the template of the vertical PVA hydrogel by electro-polymerization. When using the vertically ordered PANI as electrodes, PVA not only worked as gel electrolyte, but also provided support for excellent mechanical flexibility and durability of the electrodes. The vertical PANI@PVA electrode performed a much longer cyclic life (80% retention after 15,000 cycles) than a pure PANI electrode (80% retention after 3,000) and a disordered PANI@PVA electrode (80% retention after 4,300 cycles), benefiting from the vertical structure supported by the PVA hydrogel. Furthermore, asymmetric flexible supercapacitors (AFSCs) had been fabricated with the vertical PANI@PVA hydrogel anodes and activated carbon cathodes. The AFSCs showed excellent flexibility, high area capacity of 244 mC cm−2 at 1 mV s−1 (with a specific capacitance of 244 mF cm−2 for a voltage of 1.0 V), and superior cyclic stability with a capacitance retention of 80% after 7,000 cycles. These results strongly prove that using the polyaniline electropolymerized within a template of vertically ordered PVA as electrodes of flexible supercapacitors has a great potential in actual application.