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

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 similar to 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.