Polymer-assisted synthesis of a 3D hierarchical porous network-like spinel NiCo2O4 framework towards high-performance electrochemical capacitors

Abstract

We have developed a facile yet scalable polymer-assisted chemical solution route to prepare a three-dimensional (3D) hierarchical porous network-like NiCo₂O₄ framework for advanced electrochemical capacitors (ECs). The unique interconnected hierarchical porous framework is constructed by nanosized spinel NiCo₂O₄ building blocks of 20–30 nm size, thus, a 3D continuous electron transport expressway, convenient electrolyte penetration–diffusion and large electrode–electrolyte interface are obtained simultaneously. The combination of these appealing structural features in the striking network-like NiCo₂O₄ framework results in a drastically enhanced kinetic behavior, large specific capacitance (SC) and a remarkable cycling stability at high rates. The unique network-like NiCo₂O₄ electrode features a SC of 587 F g⁻¹ at 2 A g⁻¹, and can deliver up to 518 F g⁻¹ at a large current density of 16 A g⁻¹. Also, a SC deterioration of ∼6% of the maximum SC is evident after continuous 3500 charge–discharge cycles at varying current densities, ranging from 2 to 16 A g⁻¹. Furthermore, the synthetic strategy presented here can be easily extended to fabricate other binary complex metal oxides and/or ternary metal oxides with a controlled composition and porous structure, which may be promising candidates for high-performance ECs, and even advanced Li-ion batteries.