Engineering an Adhesive Polyphenol-Rich Hydrogel Electrolyte via ZIF-8 Reinforcement for 60% Compression-Stable Flexible Supercapacitors

Hydrogel electrolytes have been widely utilized in flexible energy-storage devices due to their high flexibility, stretchability, and tunable ionic conductivity. In this study, an anionic polyelectrolyte (PE) hydrogel was developed via free-radical copolymerization of acrylamide (AAm) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) in the presence of tannic acid (TA). TA, being polyphenolic in nature, introduces abundant dynamic noncovalent interactions, enhancing adhesion and self-recovery, while the incorporation of as-synthesized ZIF-8 nanoparticles, a porous nanofiller, provides high surface area, improved interfacial interactions (shear strength ∼141.70 kPa on metal substrate), and robust compressive resilience (39.7 kPa at 60% strain). By integrating the hydrogel electrolyte with multiwalled carbon nanotubes (MWCNTs)-based composite electrode, a flexible electric double-layer capacitor (EDLC) was assembled (specific capacitance ∼48.30 F g –1 ). The resultant supercapacitor exhibited remarkable specific capacitance retention, 85% after 1000 cycles of charging–discharging under 60% compression, and maintained stable electrochemical performance during consecutive reversible loading–unloading cycles. This work represents an effective approach in engineering PE-based advanced hydrogel electrolytes with porous nanofillers for mechanically durable, bendable, and compressible next-generation supercapacitor devices.