3D Hierarchical Ni/NiCo2O4 Core-Shell Nanotube Arrays with High Capacitance and Stable Cycling Performance for Supercapacitor

Background: Binary metal oxides, such as spinel nickel cobaltite (NiCo2O4), are attractive pseudocapacitive materials in electrochemical supercapacitors because they have higher theoretical capacitance than carbonaceous materials, and higher electronic conductivity than conventional monometal oxides. However, their practical pseudocapacitive performance is dramatically hindered by traditional electrode assembly technologies, through which extremely high internal resistances are generated at supplementary interfaces within nanostructured binary metal oxides and between binary metal oxides/current collector. Methods: Here, we develop polymer-binder-free hybrid electrodes by employing Ni nanotube arrays as 3D current collectors for the loading of electroactive NiCo2O4 nanosheets (Ni/NiCo2O4 nanotube array). Results: As a result of the remarkably enhanced electronic conductivity and ion diffusion, the Ni/NiCo2O4 nanotube array electrodes exhibit a specific capacitance of as high as ~753 F g-1 at a scan rate of 5 mV s-1 and rate performance, in addition to a long-term cycling stability. Conclusion: The outstanding performance makes the Ni/NiCo2O4 nanotube array to be an efficacious power source electrode in a wide range of applications.