Ag Nanoparticles-Decorated Bimetal Complex Selenide 3D Flowers: A Solar Energy-Driven Flexible Hybrid Supercapacitor for Smart Wearables

The demand for green-power-driven flexible energy storage systems is increasing. This requires new materials for powering wearable electronic devices without conceding energy and power densities. Herein, a nanograss-flower-like nickel di-vanadium selenide (NiV 2 Se 4 ) is fabricated on a flexible Ni–Cu–Co fabric by a scalable oil bath deposition approach. The NiV 2 Se 4 is decorated with silver (Ag) nanoparticles (NiV 2 Se 4 –Ag) to improve the electrical conductivity of the electrode surface. The NiV 2 Se 4 –Ag electrode exhibits a 27% higher capacity than the NiV 2 Se 4 electrode at 1 mA cm −2 , owing to the synergistic effect of Ag nanoparticles and NiV 2 Se 4 . Aqueous and flexible hybrid supercapacitors (HSCs) are fabricated with NiV 2 Se 4 –Ag and activated carbon (AC) electrodes (NiV 2 Se 4 –Ag//AC), which work up to 1.6 V. Aqueous NiV 2 Se 4 –Ag//AC HSCs maintain 76% capacitance at a current density of 10 mA cm −2 and deliver an energy density of 77 Wh kg −1 at a power density of 749 W kg −1 . Moreover, these HSCs exhibit an excellent cycling stability of 95% after 10,000 galvanostatic charge–discharge cycles. Ultimately, this study demonstrates the potential of NiV 2 Se 4 –Ag//AC flexible HSCs for wearable electronics. These HSCs can withstand different bending and twisting angles without compromising the electrochemical performance. The fabricated flexible HSCs can also be recharged by sunlight, providing a sustainable way to utilize natural energy resources. Graphical Abstract