Hedgehog-inspired nanostructures for hydrogel-based all-solid-state hybrid supercapacitors with excellent flexibility and electrochemical performance

Abstract

High-security deformable energy-storage devices that are mechanically robust, with considerable energy and power densities are becoming desirable for smart wearable electronics. Here, a highly flexible hydrogel-based all-solid-state hybrid supercapacitor was rationally designed and assembled, with unique NiCo₂O₄@Ni_xCo_yMoO₄ (x : y = 3 : 1) nanostructures as the electrode, which was bio-inspired by the curling up and relaxation of hedgehogs. The hybrid supercapacitor shows no obvious decay in capacitance during bending to different states, indicating its outstanding flexibility and mechanical stability. The capacitance was still maintained at 92.0% of the initial value, even after continuous bending for 3000 cycles. The highly monodisperse NiCo₂O₄@Ni_xCo_yMoO₄ nanostructures releasing stress during bending is responsible for the favorable stability and flexibility. Furthermore, the hybrid supercapacitor displayed outstanding electrochemical performance, with a high specific capacitance of 207 F g⁻¹ at 1 A g⁻¹, a high energy density of 64.7 W h kg⁻¹ at 749.6 W kg⁻¹, and favorable cycling stability (nearly 100% after 10 000 cycles). The flexible hybrid supercapacitor could be charged with a solar cell and served as the power source to light up LEDs. This simple and reliable hybrid supercapacitor, with extraordinary mechanical stability and electrochemical performance, is a promising power source for smart wearable electronics.