Tri(ethylene glycol) divinyl ether-crosslinked gel polymer electrolyte membrane with enhanced alkaline stability and electrolyte retention for flexible zinc–air batteries

Abstract

The rapidly growing field of flexible and wearable technologies has intensified the demand for the development of sustainable and flexible energy storage systems. Flexible zinc–air batteries (FZABs) are particularly promising for next-generation wearable devices, offering a high theoretical energy density of 1086 Wh/kg. The gel polymer electrolyte (GPE) in FZABs plays a crucial role in ion transport, operational stability, and cycle life while simultaneously preventing leakage associated with aqueous electrolytes. However, most existing GPEs suffer from degradation in strong alkaline environments. In this study, a chemically robust GPE crosslinked with tri(ethylene glycol) divinyl ether (TEGDE) was synthesized via photo-polymerization and explored for the first time in high-performance FZABs. The incorporation of TEGDE as a crosslinker significantly improved the chemical stability of the membrane, owing to its alkali-stable ether linkages. We show that the performance of the GPE, in terms of alkaline uptake and ionic conductivity, can be significantly tuned by controlling the initiator, monomer, crosslinker, and filler contents. The resulting membrane exhibits excellent electrolyte uptake (389%) and retention (78% after 96 h), and remarkably high ionic conductivity (339 mS cm⁻¹). It enables FZABs with a Co₃O₄ bifunctional air catalyst to run for 400 cycles over 200 hours with excellent cycling stability. Moreover, the FZABs maintain excellent performance under various bending angles, demonstrating their potential for wearable energy storage devices. These findings enhance the core understanding of structure–transport relationships in GPEs and pave the way for innovative strategies in designing high-performance membranes for FZABs.