Facilely synthesized porous NiCo2O4 flowerlike nanostructure for high-rate supercapacitors

Abstract We have developed a facile and scalable method to grow porous NiCo 2 O 4 nanostructure. The conductivity is measured by a linear sweep voltammetry, which indicates that the conductivity of the NiCo 2 O 4 sample is at least two orders of magnitude higher than those of NiO and Co 3 O 4 samples. The conductive NiCo 2 O 4 hybrid electrode delivers an enhanced specific capacitance of 658 F g −1 at 1 A g −1 compared to NiO and Co 3 O 4 . Excellent rate capability, 78% specific capacitance retention for a 20-time current density increase and 77% specific capacitance retention for a 50-time scan rate rise, is achieved. The NiCo 2 O 4 sample demonstrates ultralong cycling lifespan, no observable degradation is found for the total cycle numbers as high as 10000 cycles. Furthermore, the excellent capacitive performance of porous NiCo 2 O 4 electrode is also evaluated by a two-electrode asymmetric supercapacitor device. The asymmetric supercapacitor device delivers a 64% rate property for the current density increase 20 times. Remarkably, the asymmetric supercapacitor device also shows ultrahigh long-term stability, 93.5% of specific capacitance can still be retained after 10,000 cycles cycling. These excellent capacitive performances indicate the as-fabricated porous NiCo 2 O 4 flowerlike nanostructure a promising electrode materials for supercapacitors.