No abstract

No abstract

No abstract

Two different three-dimensional nanostructured cobalt/nickel layered double oxides grown on Ni foam (NF) were synthesized through one-step (NF/NiCo 2 O 4 ) and two-step (NF/Co 3 O 4 /NiO) solvothermal method for flexible and high performance supercapacitor applications. The as-prepared composites have been systematically characterized by powder X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The pseudocapacitive performances of composite electrode materials were investigated by the electrochemical tests. Cyclic voltammetry (CV), Galvanostatic chargedischarge (GCD) and Electrochemical impedance spectra (EIS) were performed using workstation. When the current density is 1 A/g, the capacitance of NF/Co 3 O 4 /NiO electrode material is 992 F/g; the capacitance of NF/NiCo 2 O 4 is 239 F/g. And the retention of NF/NiCo 2 O 4 electrode is 93.8% after 2000 cycles. From this comparison, it could see that the NF/Co 3 O 4 /NiO electrode exhibits more than four times higher specific capacitance at a current density of 1 A/g, good capacitance retention and excellent cycling stability than NF/NiCo 2 O 4 electrode. Furthermore that the specific capacitance of NF/Co 3 O 4 /NiO electrode increases after testing for 2000 cycles. And it can see the comparison between the interfacial charge transfer resistance (Rct) (occurring at the electrode/electrolyte interface and double layer capacitance caused by Faradaic reactions) and Warburg resistance (W), (corresponding to the ion diffusion in the host material diffusive resistance of the electrolyte in the electrode surface). The Nyquist plots are characteristic of being able to separate the charge transfer resistance and series resistance directly. However it is evident that the Nyquist plot of NF/Co 3 O 4 /NiO electrode is higher than that of NF/NiCo 2 O 4 and NF/Co 3 O 4 electrodes, demonstrating the Rct and Warburg resistance (W) of NF/Co 3 O 4 /NiO electrode is higher. The comprehensive test results show that the NF/Co 3 O 4 /NiO coreshell nanostructure arrays with remarkable electrochemical properties could be considered as potential electrode materials for next generation supercapacitors in high energy density storage systems.

No abstract