Sustainable hydrogel electrolyte with enhanced water retention and adhesion for flexible zinc–air batteries in renewable energy applications

Increasing environmental awareness is driving the demand for renewable energy and sustainable energy storage systems. Combining intrinsic safety and superior energy density, flexible zinc–air batteries (FZABs) represent a prospective direction for developing green energy conversion devices. However, the hydrogel electrolytes adopted in FZABs encounter persistent issues, such as water loss and insufficient interfacial compatibility, both of which critically limit their cycling stability and device performance. To overcome these limitations, sodium sulfamate was introduced as a functional additive to modify poly(acrylic acid) (PAA)-based hydrogel electrolytes for the fabrication of FZABs. Experimental results indicated that the operational lifespan of FZABs incorporating sodium sulfamate–modified hydrogels was extended by approximately 53.8 % compared to those using pure PAA hydrogel. The modified hydrogel exhibited excellent interfacial compatibility and strong adhesion, attributed to the presence of abundant functional groups. Moreover, these hydrogels showed remarkable flexibility and tensile strength under various mechanical deformation conditions. Additionally, the incorporation of sodium sulfamate converted free water into bound water within the gel matrix, thereby significantly improving water retention. A distinct salt precipitation phenomenon was observed, providing insights into the fundamental processes governing water loss and retention. These results provide a sustainable strategy for developing flexible zinc–air batteries as promising candidates for renewable energy storage applications.