【作者】 黄娜；

【导师】 张文魁；

【作者基本信息】 浙江工业大学 ， 应用化学， 2006， 硕士

【摘要】 目前在镍电极中，应用于实际生产的活性物质β-Ni（OH）₂的电化学容量提高的潜力有限，制备稳定且具有良好电化学性能的α-Ni（OH）₂成为研究的热点。本论文在有机溶剂中采用尿素均相沉淀法制备了Al掺杂改性的的α-Ni（OH）₂，它可以在强碱中稳定存在，并具有良好的电化学性能。 在论文的第三章中，作者先对尿素均相沉淀法的各个工艺条件对制备产物的充放电和循环性能的影响分别进行了研究，摸索出合适的工艺，即采用30％乙醇水溶液，镍盐浓度为0.7mol／L，尿素溶液的浓度为4.5 mol／L，表面活性剂为溶液总体积的1％（体积比），反应过程中将镍盐溶液和尿素溶液流速控制在0.5 mL／min，控制反应的PH值，同时快速强烈搅拌，反应温度控制在90℃±2℃，干燥温度为60℃，将会得到电化学综合性能较好，片厚约为10～20 nm、具有特殊片状微观结构的α-Ni（OH）₂，样品的放电容量达到320 mAh／g。 制备的Al取代α-Ni（OH）₂在添加CoO的条件下，放电容量接近390mAh／g，与β-Ni（OH）₂相比，充电电压低50mV左右，平均放电电压高100mV，具有良好的电化学性能。循环伏安研究表明，这种具有特殊片状结构的α-Ni（OH）₂具有很高的电化学活性，电化学可逆性良好。且其质子扩散系数远大于商业用β-Ni（OH）₂，阻抗分析也表明制备的Al取代的α-Ni（OH）₂具有较低的质子扩散阻抗。 在第五章中，制备了Al和Zn复合取代的α-Ni（OH）₂，获得一种具有特殊表面片状结构、片厚约为5～10 nm的样品。在不同含量的Al和Zn复合取代中，20％（摩尔含量）的Zn单独取代不能得到完整的α型氢氧化镍。Al和Zn的复合取代有利于降低充电电压，提高析氧电位，提高充电效率，降低晶粒尺寸和结晶度，提高样品的比表面积，使电极具有更好的反应可逆性和循环稳定性。但与Al取代α-Ni（OH）₂相比，Ni-Al-Zn-α-Ni（OH）₂在放电电压、放电容量、电化学活性等方面不具优势。交流阻抗研究表明，Ni-Al-Zn-α-Ni（OH）₂电极具有与Al取代α-Ni（OH）₂相同的阻抗等效电路图。 在第六章中，利用尿素均相沉淀法制备了Al、Co复合取代α-Ni（OH）₂，获得一种具有特殊表面片状结构、片厚约为5～15 nm的样品。与物理掺杂CoO粉末的α-Ni（OH）₂相比，Al-Co复合取代的α-Ni（OH）₂具有较低的充电电压和较高的析氧电位，具有较好的充电效率，但放电电压和放电容量则有所降低。循环伏安测试和质子扩散系数计算结果也表明，化学共沉积Al、Co复合取代α-Ni（OH）₂的电化学活性不如物理掺杂CoO粉末的Al代α-Ni（OH）₂，但适宜的Al-Co复合取代，可以较大程度地提高α-Ni（OH）₂电极的反应可逆性。更多还原

【Abstract】 It has become an important subject to prepare stable α-Ni（OH）₂ with the good electrochemical performances because the traditional active material β-Ni（OH）₂ has little improving space. In this thesis, α-Ni（OH）₂ samples with different additives which is stable in alkaline solution and has excellent electrochemical performance were prepared by homogeneous precipitation method in organic solution with urea as precipitator.In the third chapter, the effects of several conditions on homogeneous precipitation were explored in detail. The optimized technology for preparing Al-substituted α-Ni（OH）₂ was as follows: adding 0.7mol/L [Ni²⁺] solution and 4.5mol/L urea solution in 30% alcohol-water system to vessel with 1% TX-100, reacting for five hours at 90℃±2℃ with stirring, and controlling PH value and adding rate at 0.5 mL/min. The experimental results showed that a special flaky α-Ni（OH）₂ with thickness of 10-20 nm and a discharge capacity of 320mAh/g can be obtained under the optimized conditions.The electrochemical performances tests showed that the Al-substituted α-Ni（OH）₂ has the lower charging potential and the higher discharge potential than that of β-Ni（OH）₂. The results of cyclic voltammetry also showed that the as-synthesized α-Ni（OH）₂ has the better electrochemical reversibility. Al-substituted α-Ni（OH）₂ samples had higher diffusion coefficient of proton and lower charge transfer resistance than β-Ni（OH）₂ due to the large proton defects and interlayer distance.In the fifth chapter, Al-Zn co-substituted α-Ni（OH）₂ was prepared by homogeneous precipitation method. The experimental results showed that the as-prepared Al-Zn co-substituted α-Ni（OH）₂ had the special flaky surface microstructure, the flake thickness is about 5-10 nm. The pure α-Ni（OH）₂ phase can’t be obtained only by the substitution of Zn at 20%（mol）. With the substitution of Ni by Al and Zn element, the charge efficiency, crystallite size, cyclic stability and electrochemical reversibility were improved compared with that of Al-substituted α-Ni（OH）₂, however, the discharge potential, discharge capability and electrochemical activation were worsen. Electrochemical impedance spectroscopy（EIS） investigation showed that Al-Zn co-substituted α-Ni（OH）₂ and Al-substituted α-Ni（OH）₂ have the same impedance equivalent circuits.In the sixth chapter, Al-Co co-substituted α-Ni（OH）₂ was prepared by homogeneous precipitation. The results of electrochemical tests showed that the charge efficiency performance increased and the discharge potential and discharge capability tended to decreased for the Al-Co co-substituted α-Ni（OH）₂ compared with the Al-substituted α-Ni（OH）₂ with CoO additve. The results of cyclic voltammetry and proton diffusion coefficients showed that a suitable Al-Co co-substitution for Ni element in α-Ni（OH）₂ can improve the electrochemical reversibility.更多还原