Defect engineering on sea-urchin-like transition-metal oxides for high-performance supercapacitors

Reasonable design of nanostructures and application of Defect Engineering have been proved to be essential for the construction of high-performance electrochemical energy storage devices. Herein, a defect engineering strategy is developed to fabricate a 3D multi-layered sea urchin-like structure assembled by 1D nanowire, which shows a high specific surface area for electrochemical active sites. More significantly, the phosphate-doping treatment introduces N/P elements in P–NiCo2O4, thus generates Co/Ni–P and Co/Ni–N bonds to create more oxygen vacancies. Vacancy defects manipulate the electronic structure of the electrode materials to obtain good physical and electrochemical properties. The prepared sea urchin-like P–NiCo2O4 electrode in this work exhibits exceptionally excellent charge storage capability in aqueous solutions with high specific capacitance (467 C g−1 at 1 A g−1), good rate capability, and ultra-high cycling stability at 20 A g−1 (87.2% capacitance retention over 10,000 cycles). Furthermore, the assembled asymmetric supercapacitor using P–NiCo2O4 cathode and AC anode shows a high energy density of 31.25 Wh kg−1 at a much large power density of 7500 W kg−1, and an outstanding cycling performance at 10 A g−1 (83.4% capacitance retention over 10,000 cycles). The prepared P–NiCo2O4 electrode materials are expected to be used in high-performance supercapacitors.