A low cost, wide temperature range, and high energy density flexible quasi-solid-state zinc-ion hybrid supercapacitors enabled by sustainable cathode and electrolyte design

ABSTRACT Zinc-ion hybrid supercapacitor (ZHSC), emerging as a promising energy storage device, bring together the benefits of the high power density of supercapacitors, the high energy density of batteries and the environmental and cost benefits of zinc-ion technology. However, the development of high energy density ZHSC working in a wide temperature range is still a challenge. The key to achieve this target is to develop the electrolyte with thermal stability and anti-freezing property which is compatible with the advanced cathode material. Herein, a natural biomass coconut shell derived activated carbon as cathode and cost-effective aqueous Zn(ClO4)2 as electrolyte, are applied in aqueous ZHSC. The fabricated aqueous ZHSC exhibits an outstanding high energy density of 190.3 Wh/kg at 89.8 W/kg. Furthermore, a robust flexible quasi-solid-state ZHSC device was constructed by using a cross-linked poly(vinyl alcohol)/montmorillonite/Zn(ClO4)2 gel electrolyte (PVA/MMT/Zn(ClO4)2), which shows superior electrochemical performance over a wide working temperature range. Experimental analysis and molecular dynamics simulations reveal that the Zn(ClO4)2 process faster ionic migration compared to other Zn-based salts and form more hydrogen bonds with H2O, leading to a superior anti-freezing property. Our flexible device maintains the high energy storage capacities and excellent cycling stability over a wide temperature range from -50 °C to 80 °C, suggesting its great potential applications for energy storage applications in harsh environmental conditions.