Anion Modulation Enables Ambient-Temperature Dissolution of Cellulosic Biomass for Regenerated Cellulose Films and Zinc-Ion Hybrid Supercapacitors

Abstract Driven by the growing energy crisis and environmental pollution, the replacement of conventional petroleum-based products with renewable and biodegradable cellulose materials has attracted increasing attention. However, the development of green and efficient solvent systems for cellulose dissolution remains a major challenge. In this study, the effects of anion-regulated ZnCl2 and ZnBr2 aqueous solutions on cellulose dissolution behavior were systematically investigated, along with their interactions with cellulose during the dissolution process. The regenerated cellulose films were obtained via ethanol coagulation followed by hot pressing treatment. The resulting films exhibit excellent structural integrity, dense morphology, and high crystallinity, together with outstanding tensile strength (122 MPa), good thermal stability, and desirable optical properties, including high transparency and haze. Finally, the prepared cellulose hydrogels were assembled into zinc-ion hybrid supercapacitors. The devices deliver a wide operating voltage window (2 V), high energy and power densities, and excellent cycling stability, highlighting the promising potential of this solvent system for advanced cellulose-based materials and energy storage applications.