Nanowire-assembled Co₃O₄@NiCo₂O₄ architectures for high performance all-solid-state asymmetric supercapacitors

Effectively composited materials with optimized structures have exhibited promising potential in improving the electrochemical performances of supercapacitors in the past few years. Herein, we proposed a rational design to fabricate two-dimensional (2D) Co₃O₄@NiCo₂O₄ architectures composed of nanowires on a Ni foam substrate via two steps of hydrothermal processing. Owing to the high activity of the Co₃O₄ scaffolds and the well-defined NiCo₂O₄ nanowires, the hierarchical electrodes achieved remarkable electrochemical performances with a high areal specific capacitance of 9.12 F cm^-2 at the current density of 2 mA cm^-2. Both all-solid-state symmetrical supercapacitor based Co₃O₄@NiCo₂O₄//Co₃O₄@NiCo₂O₄ and asymmetric supercapacitor based Co₃O₄@NiCo₂O₄//activated carbon are fabricated with excellent electrochemical performances. The all-solid-state asymmetric supercapacitor with a maximum voltage of 1.6 V delivered a high areal specific capacitance of 1343.7 mF cm^-2 at 2 mA cm^-2, excellent cycling stability with no obvious capacitance attenuation after 5000 cycles at a current density of 10 mA cm^-2, and a high energy density of 75.6 Wh kg^-1 with a power density of 1053 W kg^-1. After rapid charging (2 s), both supercapacitors in series could light a red LED for a long time and drive a mini intelligent electronic device effectively, demonstrating advances in energy storage, scalable integrated applications and a promising commercial potential.