Ionically engineered Zn@Fe3O4 nanocomposite hydrogels with stretchable mechanics and high-performance electrochemical storage for wearable supercapacitors and strain sensors

Abstract

Herein, we report Zn@Fe₃O₄ nano-composite hydrogels (n-CHs), in which uniformly dispersed nanoparticles (NPs) within a p(AAm-co-LMA)/IGEPAL®CA-630 network reinforce the polymer structure and promote rapid ion transport. The optimized ZnF_1.00% n-CH delivers an areal capacitance (C_areal) of 954 mF cm⁻² at 2.25 mA cm⁻², retaining ∼92% of its capacitance after 10 000 charge–discharge cycles, with an average Coulombic efficiency (CE, η) of ∼99.24%, along with an energy density (E_f) of 35.5 µ W h cm⁻² and power density (P_f) of 281.3 µ W cm⁻². To validate its practical applicability, a flexible soft-pack supercapacitor (SC) was assembled, which exhibits an areal capacitance of 525.4 mF cm⁻², an energy density of 146 µ W h cm⁻², and a power density of 2625 µ W cm⁻² at a high current density (I_{areal, f}) of 4.50 mA cm⁻², demonstrating high performance in deformable, large-area configurations. Additionally, the hydrogel functions as a sensitive strain sensor, with a gauge factor (GF) of 5.12 at 700% strain and a reproducible response under repeated deformation. By bridging high-performance energy storage with sensitive, stretchable sensing, Zn@Fe₃O₄-reinforced hydrogels provide a foundation for resilient, multifunctional soft devices.