Pullulan enhanced dual-network hydrogel electrolyte for high-performance flexible zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) offer significant advantages, including low cost, high capacity, and safety. However, challenges such as zinc dendrites and uncontrollable side reactions hinder their widespread application. Hydrogel electrolytes can effectively inhibit the growth of negative dendrites and reduce side reactions associated with zinc electrode. Moreover, hydrogel electrolytes confer flexible and wearable characteristics ZIBs, making them suitable for applications in flexible electronics and wearable devices. Herein, we develop novel dual-network hydrogel electrolyte (PPZ) made by incorporating pullulan (PuL) into polyvinyl alcohol (PVA) hydrogel, enhancing its tensile strength and adhesion performance. The developed PPZ hydrogel trolyte weakens the solvation of zinc ions, enabling stable and uniform plating/stripping behavior of the Zn metal anode during long-term cycling. The Zn//Zn symmetric cell with PPZ hydrogel electrolyte exhibits outstanding cycling stability (1800 h) at a current density of 0.5 mA cm- 2. Furthermore, the Zn//PPZ//PANI@TOC flexible ZIB maintains a capacity retention rate of 87.42 % after 6,000 cycles at 2 mA cm- 2 and undergoes 3,000 bends 180 degrees with a high capacity retention rate of 87.53 %. This research provides a high-performance dual-network hydrogel electrolyte for designing multifunctional flexible energy storage and wearable electronic devices.