Long-Term Stability of Hygroscopic Hydrogels by Preventing Metal Ion-Mediated Degradation

Recent developments in material chemistry highlight hygroscopic hydrogels as promising candidates for use in sorption systems, with applications ranging from atmospheric water harvesting to energy storage and thermal management. However, material lifetime remains a significant limitation to realizing cost-effective high-performance devices. In this work, we consider deployment of lithium chloride-loaded polyacrylamide (PAM + LiCl) hydrogels at elevated temperatures on a variety of potential system substrates, correlating lifetime and cyclability of the gels to device design and material choice. We show that the presence of metallic ions in the system leads directly to material degradation via radical formation in the gels. Moreover, metallic ion absence results in consistent cyclic sorption performance and a gel lifetime of over 8 months. This work demonstrates the long-term stability of PAM + LiCl hydrogels, and provides initial design guidelines for its repeatable, cost-effective implementation in future sorption systems.