Dendrite‐Free Zinc Ion Hybrid Supercapacitors with ZnCl₂‐Modified Lignocellulose Hydrogel Electrolyte for Modulating Zinc Ion Solvation and Directed Deposition

Chargeable-dischargeable zinc-ion hybrid supercapacitors (ZHSCs) face significant challenges regarding low coulombic efficiency and short cycle life, primarily due to water-induced side reactions and uncontrolled zinc anode dendrite growth. Herein, a Zn-friendly hydrogel electrolyte is developed using ZnCl2-modified lignocellulose (LC), which effectively facilitates the coordination of Zn2+ with -OH by disrupting the strong hydrogen bonding between the LC chains, exposing more -OH binding sites, and thus modulating the deposition behavior and interfacial chemistry of Zn on the Zn electrode. Experimental results and theoretical calculations demonstrate that the formed solvated Zn2+ effectively suppresses the undesirable hydrogen evolution reactions (HER). Meanwhile, the abundant -OH groups in LC affect the adsorption conformation of solvated Zn2+. This promotes a directed deposition (0 0 2) process that prevents dendrite growth and facilitates the directed deposition with rapid reaction kinetics at the zinc electrode. As a result, the Zn//Zn symmetric cell demonstrates high reversibility in deposition/stripping behavior with a cycle life exceeding 2800 h. Notably, the assembled Zn//ZnCl2+LC//AC full cell achieves exceptional cycling stability over 11 000 cycles, while the Zn//NVO full cell maintains stable cycling performance for over 3500 cycles.