Synthesis of Ni(OH)2 by Template Homogeneous Precipitation for Application in the Binder­free Electrode of Supercapacitor

Nickel hydroxide is widely used as the active material for hybrid supercapacitors. The most electrochemically active is α-Ni(OH)2, synthesized using template homogeneous precipitation. The disadvantage of template homogeneous synthesis is the inclusion of the template into the composition of nickel hydroxide and the necessity of its removal. In order to reverse this disadvantage, it was proposed to study the possibility of using the remaining template as an inner binder for the preparation of a highly effective pasted supercapacitor electrode, without an external binder. Samples of Ni(OH)2 were prepared by means of template homogeneous precipitation, with polyvinyl alcohol and cellulose ester Culminal C8465 with the concentration of 0.05 % and 0.5 %. Structural properties of the samples were studied by means of X-ray diffraction analysis, particle size and morphology — by means of scanning electron microscopy. Electrochemical properties of nickel hydroxide were evaluated by means of galvanostatic charge-discharge cycling of the pasted electrode prepared without a binder, in the supercapacitor regime. It was discovered, that the use of PVA results in significantly higher crystallinity and lower agglomerate formation. Increasing PVA concentration by 10 times had no effect on these characteristics. For Culminal C8465, the crystallinity is significantly lower, but it increases with template concentration. Higher concentration of Culminal C8465 also leads to significant particle aggregation. Different behavior of PVA and Culminal C8465 has been revealed. PVA behaves like a weak binder and Culminal C8465 shows strong binding properties. Complex analysis of electrochemical characteristics of pasted electrodes prepared without a binder confirmed the possibility of using the remaining template as an inner binder. The highest specific capacity for the electrode without an external binder was 197 F/g when Culminal C8465 was used as a template. It is recommended to conduct the selection of a water-soluble compound that would play the role of a template during the synthesis of nickel hydroxide and would also serve as a binder for the preparation of pasted electrod