Hybrid hydrogel electrodes for highly stretchable and high-capacitance flexible supercapacitors

Flexible supercapacitors (FSCs), driven by the urgent demand for lightweight and multifunctional wearable electronics, have rapidly advanced owing to their simple configuration, high electrochemical stability, and power density. However, achieving high specific capacitance and stable output under extreme deformations, particularly large tensile strains, remains a critical challenge. Herein, we report an intrinsically stretchable PVA/PEDOT/CNT/PANI hybrid hydrogel (PVCPH), engineered through sequential freeze-salting-out and acid treatment to form a 3D hierarchical framework. In this architecture, the PVA backbone provides reversible macroscopic elasticity, the PEDOT/CNT network establishes a continuous mesoscopic pathway for charge transport, and proton-doped PANI nanospheres serve as highly effective microscopic pseudocapacitive contributors. Owing to this hierarchical integration, PVCPH exhibits remarkable stretchability (301.35%±5.46%) while delivering a high specific area capacitance (CA) of 2001 mF cm⁻². Even in quasi-solid-state devices with gel electrolytes, the FSCs maintain a CA of 1513 mF cm⁻² and achieve an outstanding energy density of 135 µWh cm⁻². Furthermore, the devices preserve nearly 100% capacitance after repeated cycles of stretching, bending, and twisting, highlighting their robustness under extreme mechanical conditions. These results establish a viable strategy for designing deformation-tolerant FSCs capable of powering next-generation wearable electronics.