Mesoporous NiCo2O4 nanospheres with a high specific surface area as electrode materials for high-performance supercapacitors

Abstract

Ternary nickel cobaltite (NiCo₂O₄) has attracted more and more attention as a promising electrode material for high performance supercapacitors (SCs) due to its high theoretical capacity, unique crystal structure and excellent electronic conductivity. In this study, a template-free chemical co-precipitation method as a general strategy has been easily developed to fabricate mesoporous NiCo₂O₄ nanospheres with a high specific surface area of 216 m² g⁻¹, which can be further self-assembled into 3D frameworks. The key to the formation of mesoporous NiCo₂O₄ nanospheres with a desired pore-size distribution centered at ∼2.4 nm is a unique preparation method assisted with sodium bicarbonate as a complex agent. When tested as electrode materials for SCs, the NiCo₂O₄ electrodes delivered excellent electrochemical performances with high specific capacitance (842 F g⁻¹ at a current density of 2 A g⁻¹), superior cycling stability with no capacity decrease after 5000 cycles (103% initial capacity retention), and great rate performance at a 10-time current density increase (79.9% specific capacitance retention). Furthermore, as expected in a NiCo₂O₄-based asymmetric supercapacitor device, a superior energy density as high as 29.8 W h kg⁻¹ at a power density of 159.4 W kg⁻¹ could be achieved. These results highlight a general, eco-friendly, template-free strategy for the scale-up fabrication of a promising mesoporous NiCo₂O₄ electrode material for high-performance SC applications.