Controlling Dendrite Growth with Xylan-Enhanced Hydroxyl-Rich Hydrogel Electrolyte for Efficient Zn-Ion Energy Storage

The development of sustainable and safe energy storage systems is becoming increasingly important, which will drive the boom of aqueous Zn-based energy storage devices. However, it is challenging to overcome the dendrite and side-reaction issues of Zn anodes and extend the applications of devices. Herein, we design a polysaccharide-enhanced hydrogel electrolyte (PBXHE: PVA/Borax/Xylan/Zn(OTf) 2 ) with OH-rich xylan to tackle these problems. The resultant PBXHE, dually cross-linked chemically and physically, showcases mechanical robustness. The incorporated xylan polysaccharide facilitates the formation of a well-developed interconnected porous network within the hydrogel, promoting electrolyte ion mobility. Concurrently, the coordinated interaction between the polar hydroxyl groups in xylan and polyvinyl alcohol (PVA) induces the uniform deposition of zinc ions. Therefore, the symmetric Zn|PBXHE|Zn cell exhibits remarkable durability, operating continuously for 520 h at 1 mA cm –2 and accumulating a total capacity of 3000 mA h cm –2 at 20 mA cm –2 . The as-fabricated hydrogel-based zinc-ion hybrid capacitor retains almost 90% of its initial capacity after 20,000 cycles, with a peak energy density of 82.1 W h kg –1 at 193.7 W kg –1 power density. This work provides a feasible strategy for engineering environmentally benign polysaccharide-assisted hydrogel electrolytes to protect Zn anodes for the sustainable development of competitive Zn-based energy storage devices.