Ionically Engineered Zn@Fe 3 O 4 Nanocomposite Hydrogels with Stretchable Mechanics and High-Performance Electrochemical Storage for Wearable Supercapacitors and Strain Sensors

Abstract

Herein, we report Zn@Fe 3 O 4 nano-composite hydrogels (n-CHs), with 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 area specific capacitance (C areal ) of 954 mF cm -2 at 2.25 mA cm -2 , retaining ~92% after 10,000 charge-discharge cycles with an average of ~99.24% coulombic efficiency (CE, ƞ), along with energy density (E ) of 35.5 µWh cm -2 and power density (P ) of 281.3 µW cm -2 . To validate its practical applicability, a flexible soft-pack supercapacitor (SC) assembled which exhibits 525.4 mF cm -2 areal capacitance, 146 µWh cm -2 energy, and 2625 µW cm -2 power at high current density (I areal, ) 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 reproducible response under repeated deformation. Bridging high-performance energy storage with sensitive, stretchable sensing, Zn@Fe 3 O 4 -reinforced hydrogels provide a foundation for resilient, multifunctional soft devices.