A Stretchable and Highly Conductive Flexible Hydrogel Electrolyte for Supercapacitor

Highly conductive hydrogel electrolytes have substantially promoted the advancement of flexible electronic devices. For such electrolytes, addressing the intrinsic trade-off between mechanical integrity and electrical conductivity is crucial for achieving optimal performance. This study investigates a composite hydrogel composed of cellulose nanofiber (CNF) and polyacrylamide (PAM), in which the interaction between CNF and PAM forms a stable structural network and facilitates efficient ion transport pathways. Furthermore, the incorporation of ferrous acetate (Fe(CH₃COO)₂) encapsulated within β-cyclodextrin (β-CD@Fe) into the hydrogel matrix markedly improves the ionic conductivity and enables a favorable balance between mechanical strength and electrical conductivity. As a result of this innovative design, the hydrogel exhibits excellent electrochemical properties, including an ionic conductivity of 0.0514 S cm −1 and a specific capacitance of 37.8 F cm −2 . Notably, the hydrogel maintains excellent cycling stability, retaining a Coulombic efficiency of 97.32% after 2000 charge–discharge cycles. Coupled with its combination of robust adhesion, self-healing capabilities, and exceptional mechanical durability alongside superior electrochemical performance, this hydrogel is a promising candidate for high-power-density, long-cycle-lifetime energy storage systems.