Zinc ion trapping in a cellulose hydrogel as a solid electrolyte for a safe and flexible supercapacitor

A flexible zinc-ion hybrid supercapacitor (ZHS) was constructed using a solid-state cellulose hydrogel electrolyte containing a high concentration of ZnCl 2 . This biodegradable cellulose hydrogel electrolyte can afford a wide electrochemical potential window and excellent ionic conductivity, resulting in a ZHS with an extremely high capacity of 193 mA h g −1 , an energy density of 192 W h kg −1 , and a power density of 16 976 W kg −1 . The flexible ZHS also shows excellent stability and can work at low temperature of −20 °C. This work progresses the field of Zn-based electrochemical energy storage devices and gives a meaningful guide for the design of solid-state electrolytes. High concentrated ZnCl 2 is trapped in a biodegradable cellulose hydrogel as electrolyte for a flexible zinc-ion hybrid supercapacitor (ZHS). Such ZHS has a wide electrochemical potential window and extremely high energy/power density.