Advances in Functional Cellulose Hydrogels as Electrolytes for Flexible Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) emerge as leading candidates for a flexible energy storage system, distinguished by high capacity, affordability, and inherent safety. The integration of hydrogel electrolytes, particularly those with saturated aqueous solvents, has significantly enhanced the electrochemical performance of ZIBs while preserving their essential flexibility. Nonetheless, challenges in electrochemical performance under specific conditions highlight the nascent stage of this technology, with numerous technical hurdles awaiting resolution. Addressing these challenges, recent investigations have leveraged the unique properties of cellulose hydrogel—namely, its exceptional toughness, tensile strength, extreme temperature resilience, stimulus responsiveness, and self-healing capabilities—to innovate multifunctional flexible zinc-based batteries. This paper conducts a comprehensive review of the physicochemical attributes of cellulose hydrogel electrolytes within ZIBs. We thoroughly analyze their performance under diverse environmental conditions, offering insights into the current landscape and their future potential. By examining these aspects, we aim to underscore the developmental prospects and the challenges that lie ahead for hydrogel electrolytes in ZIBs, paving the way for further advancement in this promising field.