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 ZnCl2. 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 degrees 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.