Design of ZIF-8-Reinforced Dynamically Cross-Linked Hydrogel Electrolyte for Robust and Flexible Supercapacitor Devices

Gel polymer electrolytes (GPEs) have emerged as critical components for next-generation flexible supercapacitors owing to their soft and deformable nature, tunable physicochemical properties, and improved safety compared to conventional liquid electrolytes. Despite these advantages, the simultaneous integration of mechanical robustness, self-healing capability, and high ionic conductivity remains a major challenge, limiting their practical applicability. In this work, a borate ester-based dynamically cross-linked hydrogel electrolyte is developed, reinforced with zeolitic imidazolate framework-8 (ZIF-8) nanoparticles. The incorporation of ZIF-8 introduces additional physical cross-linking sites within the copolymer matrix, thereby enhancing mechanical integrity, as demonstrated by a compressive stress of 45.4 kPa at 60% strain, validated using the Ogden hyperelastic material model. The hydrogel thin film exhibits a self-healing efficiency of 54% at room temperature. Furthermore, the nanoporous structure of ZIF-8 functions as an ion reservoir, facilitating enhanced LiCl uptake and leading to a high ionic conductivity of 40 mS cm –1 . When employed as electrolyte in a fabric-based electric double-layer capacitor (EDLC), the composite hydrogel enables superior capacitive performance, increasing from 30.80 F g –1 in the flat state to 49.76 F g –1 under 120° bending, while ensuring full recovery under repeated folding-unfolding cycles. Self-healed devices also preserved stable operation, sustaining bending up to 30° with a Coulombic efficiency above 80%. Beyond EDLCs, integration of the hydrogel electrolyte with polyaniline (PANI)-based electrodes in a pseudocapacitor assembly achieved a high specific capacitance of 146.70 F g –1 and a remarkable power density of 187.77 W kg –1 at 0.30 A g –1 . Collectively, these findings demonstrate that the ZIF-8-reinforced dynamic borate ester hydrogel effectively balances mechanical resilience, self-healing, and ionic conductivity, establishing its substantial potential for flexible and wearable energy storage applications.