Applications of Hydrogels for Next-Generation Batteries.

Hydrogels have garnered significant attention as multifunctional materials in next-generation rechargeable batteries due to their high ionic conductivity, mechanical flexibility, and structural tunability. This review presents a comprehensive overview of hydrogel types-including natural, synthetic, composite, carbon-based, conductive polymer, and MOF hydrogels-and their synthesis methods, such as chemical crosslinking, self-assembly, and irradiation-based techniques. Characterization tools like SEM, XRD, and FTIR are discussed to evaluate their microstructure and performance. In rechargeable batteries systems, hydrogels enhance ionic transport and mechanical stability, particularly in lithium-ion, sodium-ion, zinc-ion, magnesium-ion, and aluminum-ion batteries. Despite their advantages, hydrogels face challenges such as limited mechanical strength, reduced stability under extreme conditions, and scalability issues. Current research focuses on advanced formulations, self-healing mechanisms, and sustainable materials to overcome these limitations. This review highlights the pivotal role of hydrogels in shaping the future of flexible, high-performance, and environmentally friendly secondary batteries.