Multiscale dual-network cellulose hydrogel electrolytes for dendrite-free Zn anode

Aqueous zinc-ion batteries (AZIBs) have emerged as promising energy storage systems owing to their high safety, low cost, and environmental friendliness. However, their practical application faces critical challenges, including the formation of Zn dendrites and the occurrence of parasitic side reactions. These phenomena not only hinder ion transport kinetics but also cause rapid capacity decay and potential battery failure. To address these limitations, we developed a sustainable double-crosslinked cellulose hydrogel electrolyte by integrating micron-sized cellulose and cellulose nanofibers (CNFs). The hydrogel electrolyte, constructed from cellulose components with distinct size scales, exhibits a well-organized hierarchical porous network structure, which significantly facilitates the migration of zinc ions. Specifically, nanocellulose serves as a reinforcing filler that enhances the mechanical strength of the dual-network electrolyte, thereby inhibiting Zn dendrite growth. Additionally, abundant carboxyl polar functional groups were also introduced as high-affinity Zn 2+ binding sites to mitigate side reactions. Consequently, the assembled Zn//Zn symmetric cells with this electrolyte demonstrate superior cycling stability exceeding 1 100 h at current density of 0.5 mA/cm 2 , along with a high-capacity retention of 79.9% after 1 000 cycles in the Zn//V 2 O 5 battery. Furthermore, this cellulose hydrogel electrolyte is easily accessible and biodegradable, paving the way for the scalable production of high-performance and environmentally friendly energy storage devices.