Flexible quasi-solid-state zinc-ion hybrid supercapacitor based on carbon cloths displays ultrahigh areal capacitance

Over the past few years, the flexible quasi-solid-state zinc-ion hybrid supercapacitors (FQSS ZHSCs) have been found to be ideal for wearable electronics applications due to their high areal capacitance and energy density. The assembly of desirable ZHSCs devices that have promising practical applications is of high importance, whereas it is still challenging to assemble ZHSCs devices. In this study, a ZHSC that exhibited ultrahigh areal capacitance and high stability was developed by using an active carbon cloth (ACC) cathode, which could improve ionic adsorption. The as-obtained ACC cathode had an energy storage mechanism due to the electrical double-layer capacitive behavior of Zn2+, which was accompanied by the dissolution/deposition of Zn4SO4(OH)6·5H2O. The ACC//Zn@ACC ZHSC device exhibited an areal capacitance of 2437 mF cm−2 (81 F cm−3, 203 F g−1 under the mass of ACC with ∼12 mg cm−2) at 1 mA cm−2, an areal energy density of 1.354 mWh cm−2 at 1 mW cm−2, as well as high stability (with an insignificant capacitance decline after 20000 cycles), which was demonstrated to outperform the existing ZHSCs. Furthermore, the assembled flexible device still had competitive capacitance, energy density and service life when integrated into a FQSS ZHSC. When applied in practice, the device could achieve high mechanical flexibility, wearable stability and output. This study can inspire the development of the FQSS ZHSC device to satisfy the demands for wearable energy storage devices with high performance.