SUMMARY
Binary Ni-Co compounds, namely oxyhydroxides and cobaltates of nickel, are promising active compounds for supercapacitors. The characteristics of binary Ni-Co oxyhydroxides synthesized using the method of high-temperature two-stage synthesis with hot and cold hydrolysis were studied. The crystal structure of the samples was studied by means of X-ray diffraction and thermogravimetry, particle morphology –scanning electron microscopy, electrochemical characteristics – cyclic voltammetry and galvanostatic charge-discharge cycling.By means of scanning electron microscopy, it was found that the samples of cold and hot hydrolysis are nano-structured powders composed of flower-like particles, composed of 70–90 nm thick plates. The results of XRD and thermogravimetric analyses revealed that both samples are binary Ni-Co oxyhydroxides (hydrated nickel cobaltates with different hydration levels) with the presence of pure nickel cobaltate. Hot hydrolysis samples contain less water and more nickel cobaltate. Cyclic voltammetry and galvanostatic charge-discharge cycling revealed that in the cold hydrolysis Ni-Co sample, only the nickel component is electrochemically active. The maximum capacity of the cold hydrolysis sample is 185.7 F/g (at 10 mA/cm2). With the increase of current density to 120 mA/cm2, the specific capacity drops by 4.47 times. The hot hydrolysis sample was found to have both nickel and cobalt components active: the sample having increased capacity with increasing current density from 10 mA/cm2 to 120 mA/cm2 by 1.25 times, up to 192.5 F/g. The hot hydrolysis sample was found to possess high reversibility and high effectiveness of the electrochemical component from cycle 1