| Nickel hydroxide as the variety of the positive active material of the alkaline battery, playing a key role in the battery capacity, lifetime and the electrochemical properties. Nickel hydroxide has two forms, one kind is α-Ni(OH)2, the other is β-Ni(OH)2, these shape and structure were similar, and be composed of NiO2layer board, mixed water molecules and some anions exit between the layers.β-Ni(OH)2layer board parallel stack structure, cell arranged neatly, but α-Ni(OH)2layer board stack structure was the "turbulence" structure, which is the stack of make hole in crystal structure, electron transfer number is more, so that the α-Ni(OH)2than β-Ni(OH)2has higher theoretical specific capacity; However a-Ni(OH)2of the "turbulence" structure also has shortcomings, which was not stable in alkaline environment,water molecules or anion between layers can be replaced by OH", translate to be β-Ni(OH)2. At present,β-Ni(OH)2which the application in practical production electrochemical capacity is close to the theoretical value, have no potential basically, therefore, preparation of stable and have good electrochemical properties of α-Ni(OH)2is becoming a hot spot of research.Pure phase a-Ni(OH)2samples were successfully prepared with urea and nickel nitrate hexahydrate as raw material by hydrothermal method, and these particles with the smaller particle size, uniform particle size and bigger specific surface area. It was discussed in detail the influence on the reactant concentration, material ratio, reaction temperature, reaction time and so on factors, and the products were characterized by X-ray diffraction (XRD), particle size analysis, BET, FT-IR and cyclic voltammetry. The results showed that the sample synthetized by hydrothermal method (the nickel concentration was0.05mol/L, the molar ratio of the CO(NH2)2to Ni(NO3)2·6H2O was3:1, water hot temperature was150°and reaction time was4h) was the pure α-Ni(OH)2with the particle diameter mainly distributing between the10.09μm and22.79μm, the specific surface area as large as61.64m2/g, the differentials between oxidation potential and reduction potential was0.2V, so electrochemical reversibility is poorer and the materials need to be optimized the on reversibility of electrochemical; the differentials between oxygen evolution potential and oxidation potential was0.16V, has yet to be improved in inhibition of oxygen evolution reaction.In order to gain more excellent performance of α-Ni(OH)2, this work with the introduction of Al, zinc, zinc/Al composite doping into Ni(OH)2lattice, α-Ni(OH)2synthesised was stable in alkaline solution and has a better cycle performance.After the Al instead of α-Ni(OH)2preparated by the hydrothermal, having a series of discussion to it on synthetic process conditions,the results show that when α-Ni(OH)2of Al instead of20%,、25%and the molar ratio of urea and metal salt is3:1, crystallization is better, but the reaction time and reaction temperature on the crystal type of influence was not obvious; Particle size of Al instead of α-Ni(OH)2was mainly distributed in15to30μm, average particle size was17.29μm, SBET=67.21m2/g, and stable in alkaline environment;the differentials between oxidation potential and reduction potential was0.24V, the differentials between oxygen evolution potential and oxidation potential was0.10V; compared with single α-Ni(OH)2, the reversibility and inhibition of oxygen evolution reaction has not improved. After preparated zinc replaced α-Ni(OH)2by the hydrothermal, having a series of discussion to it on synthetic process conditions, the results show that influence of the amount of zinc replaced, the molar ratio of urea and metal salt, reaction time and reaction temperature on the crystal type is not obvious,only slight changes; Particle size of Zn instead of α-Ni(OH)2was mainly distributed in10to25μm,average particle size was14.34μm, SBET=118.67m2/g, and stable in alkaline environment;the differentials between oxidation potential and reduction potential was0.16V, the differentials between oxygen evolution potential and oxidation potential was0.05V; compared with single α-Ni(OH)2, the differentials between oxidation potential and reduction potential was reduced by0.04V, zinc doping makes improved in reversible. After preparated of Al/zinc composite instead of α-Ni(OH)2the hydrothermal, having a series of discussion to it on synthetic process conditions, the results showed that when the mole ratio of urea and metal salt was5:1, the sample have better crystallization, effect of reaction time and reaction temperature on the crystal type is not obvious; Particle size of Al/Zn instead of α-Ni(OH)2was mainly distributed in5to15μm, average particle size was10.78μm, SBET=146.59m2/g, and stable in alkaline environment;the differentials between oxidation potential and reduction potential was0.16V, the differentials between oxygen evolution potential and oxidation potential was0.11V; compared with single α-Ni(OH)2, the differentials between oxidation potential and reduction potential was reduced by0.04V, that doping with Al/zinc makes the α-Ni(OH)2has better electrochemical reversibility; And compared with Al replace α-Ni(OH)2and zinc replaced α-Ni(OH)2, charge and discharge performance and charging efficiency have been promoted. |
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