Dual-source zinc strategy enables homogeneous cellulose/DES gel electrolytes with wide voltage windows for zinc-ion hybrid capacitors

Cellulose-based hydrogels are promising for flexible energy storage, but their electrochemical stability window (ESW) and environmental tolerance are often limited in aqueous environments. In aqueous energy storage devices, tailoring the solvation sheath to suppress parasitic side-reactions key to expanding the ESW. Herein, we propose a “dual-source Zn” strategy that successfully fabricates a uniform, highly stable, water-lean cellulose/DES gel electrolyte (CDE) through multiscale and multidimensional molecular engineering of the cellulose network and solvation environment. This strategy creates a unique anchoring-conducting composite microstructure: internal zinc acts as a structural anchor, strongly coordinating with the cellulose backbone to form a stable, pre-crosslinked network. This not only prevents surface densification during phase inversion but also facilitates the uniform permeation of the external DES and zinc salt. The external zinc, in turn, functions as a mobile charge carrier, facilitating ion conduction within the confined nanochannels formed by this matrix. Microstructural characterizations confirm that this unique synergistic effect effectively suppresses highly active water while preserving efficient ion transport pathways. Consequently, the resulting electrolyte exhibits a remarkable 3.3 V voltage window, an excellent zinc-ion transference number (0.82), and a highly competitive ionic conductivity of 9.86 mS cm −1 under water-lean conditions. Zinc-ion hybrid supercapacitors (ZHSCs) assembled with this electrolyte deliver an outstanding specific capacity of 140.3 mAh g −1 at 1 A g −1 and demonstrate exceptional long-term cycling stability (92.5% retention after 1500 cycles).