Electroconversion synthesis of Ni/Co layered nanomaterials for high-performance supercapacitors

Ni/Co(OH)2 nanosheets were prepared through an electroconversion reaction with CoCl2.6 H2O and NiCl2.6 H2O as raw materials and without an added structural guiding agent. NiCo2O4 was obtained by calcination with Ni/Co(OH)2 as a precursor. The structure and morphology of Ni/Co(OH)2 and NiCo2O4 were characterized by XRD, FTIR, XPS, and SEM. The characterization results show that the particle size range of Ni/Co(OH)2 with a three-dimensional nanostructure is 10-84 nm, and it is formed by staggered stacking of nanosheets with a thickness of approximately 19 nm. The electrochemical test results show that the specific capacitance of the Ni/Co(OH)2 nanosheet electrode in 1 M KOH electrolyte and 1 A/g current density is as high as 908.33 F/g, which can be attributed to its unique three-dimensional nanolayered structure, and as a result, more redox reaction active sites can be provided in the charge storage process. In addition, the structure of the Ni/Co(OH)2 nanosheet electrode can slow down the volume change during the charge- discharge cycle and maintain the stability of the structure. Under the high current density of 10 A/g, the specific capacitance retention rate is 71% at 1500 cycles and 74% at 3500 cycles, but then it shows a downwards trend. The capacitance retention rate fluctuates between 60% and 30%. After 10000 cycles, the specific capacitance retention rate is still 30%, indicating that the electrode exhibits a good cycle performance.

Automated summary

Ni/Co(OH)2 nanosheets were prepared through an electroconversion reaction and then calcined to obtain NiCo2O4. The resulting nanosheets exhibit a three-dimensional nanostructure with specific particle size range and stacked nanosheets. The electrochemical tests demonstrate the high specific capacitance and good cycle performance of the Ni/Co(OH)2 nanosheets electrode.