Facile Synthesis of NiCo₂O₄ Nanowire Arrays/Few-Layered Ti₃C₂-MXene Composite as Binder-Free Electrode for...

Herein, a 3D hierarchical structure is constructed by growing NiCo₂O₄ nanowires on few-layer Ti₃C₂ nanosheets using Ni foam (NF) as substrate via simple vacuum filtration and solvothermal treatment. Ti₃C₂ nanosheets are directly anchored on NF surface without binders or surfactants, and NiCo₂O₄ nanowires composed of about 15 nm nanoparticles uniformly grow on Ti₃C₂/NF skeleton, which can provide abundant active sites and ion diffusion pathways for enhancing electrochemical performance. Benefiting from the unique structure feature and the synergistic effects of active materials, NiCo₂O₄/Ti₃C₂ exhibits a high specific capacitance of 2468 F g^-1 at a current density of 0.5 A g^-1 and a good rate performance. Based on this, an asymmetric supercapacitor (ASC) based on NiCo₂O₄/Ti₃C₂ as positive electrode and activated carbon (AC)/NF as negative electrode is assembled. The ASC achieves a high specific capacitance of 253 F g^-1 at 1 A g^-1 along with 91.5% retention over 10,000 cycles at 15 A g^-1. Furthermore, the ACS presents an outstanding energy density of 90 Wh kg^-1 at the power density of 2880 W kg^-1. This work provides promising guidance for the fabrication of binder-free, free-standing and hierarchical composites for energy storage application.