Synthesis And Electrochemical Properties Of Nickel-Cobalt Hydroxide As Electrode Materials For Supercapacitor

Supercapacitor is a new type of energy storage devices between the typicaldielectric capacitors and chemical batteries. It has high energy density, high powerdensity, long cycle life characteristics. Because of its excellent electrochemicalproperties such as high theoretical capacity, relatively low price. Hydroxides of nickeland cobalt has been regarded as a very promising electrode material forsupercapacitors.A typical template-assisted Hydrothermal Synthesis progress was used toprepared Ni（OH）₂. X-ray diffraction showed that the sample is α-Ni（OH）₂. Theelectrochemical test results showed that the samples of the nickel hydroxide havegood pseudo-capacitance characteristics, whose specific capacitance at the currentdensity of1A/g reaches the maximum648F/g.Another bath sponge-like Ni（OH）₂was prepared by template-free HydrothermalSynthesis method. the conjecture of the growth mechanism of the morphology of thematerial was postulated in this paper. The growth mechanism: nucleation-amorphousNi（OH）₂-layered growth-forming-connection. And by the similar properties ofHMT （hexamethylenetetramine）, N₂H₄·H₂O （hydrazine）, the NH₃·H₂0（ammonia） toverify the above conjecture. By means of electrochemical tests, withouttemplate-assisted hydrothermal synthesised Ni （OH）2whose specific capacitance still214.6F at current density of15A/g was prepared.It is certified that this sample is anexcellent material for supercapacitors.Some different sample of proportions of the Ni-Co hydroxide were prepared inthe conditions of template agent and template-free agent. It is found that when a Ni:Co’s ratio is about1:1, Ni（OH）₂and Co（OH）2oxidation reduction reaction match witheach other well. And the appropriate cyclic voltammetry curve closest to the idealcurve, which means good reversibility. It is proved that getting rid of theexpensive and toxic templating agent, the material synthesised by hydrothermal method still has good electrochemical properties. So thismethod is an effective synthesis method of Ni-Co hydroxide basedsupercapacitor electrode material.