【作者】 赵卫民；

【导师】 刘长久；

【作者基本信息】 桂林理工大学 ， 应用化学， 2010， 硕士

【摘要】 论文全面综述了α-Ni(OH)2电极材料作为MH-Ni电池正极活性物质的研究现状。基于稀土元素物质独特的电子组态及4f电子运动特性,并考虑到相关金属离子的电化学功能性作用,采用尿素均相沉淀法成功制备出稀土La掺杂Zn/Al取代α-Ni(OH)2粉体材料,并系统研究了其制备合成条件及行为规律,测试分析了所制备材料的物理特性及其微结构特征,研究考察了样品材料电极的电化学性能及材料的掺杂元素组成、含量对其微结构及其电极材料在电极过程中的电化学活性效应与电化学性能的影响,并讨论了其内在联系机制的电化学作用机理。文中通过采用尿素用量、反应温度、反应时间、分散剂等单因素对电极材料性能影响的实验研究,确定出尿素均相沉淀法制备La掺杂Zn/Al取代α-Ni(OH)2稳定结构粉体材料的优化体系工艺条件为:乙醇-水溶液体系,尿素与金属盐比例为30:1、反应温度控制在90±1℃、搅拌反应3h、粉体干燥温度为60℃。实验研究结果发现,在确定的优化工艺条件下制备出不同比例配制量的La掺杂Zn/Al取代α-Ni(OH)2样品粉体材料,形貌为无数片状微晶相互粘连且具有较多孔隙的类球状颗粒。样品材料经XRD、Raman、IR和TG-DSC测试结果表明,材料的微结构比Zn/Al取代α-Ni(OH)2具有较多的微结构缺陷和较大层间距,并含有较多结晶水,同时热稳定性明显增强。将其合成MH-Ni电池正极材料的电化学性能测试结果表明,当La掺杂摩尔用量为5%的Zn代α-Ni(OH)2的样品材料电极在0.1C放电下,其放电比容量达382.85mAh·g-1,放电中值电压较高并稳定于1.2943V,在1.0C下,放电比容量为359.85mAh·g-1,经30次充放电循环后样品电极容量保持率达到91.04%;La掺杂Al取代α-Ni(OH)2的样品材料电极在0.1C下放电,La掺杂摩尔含量为5%的样品材料电极放电比容量高达404.95mAh·g-1,放电中值电压为1.2968V,在1.0C倍率下的充放电循环测试结果表明,经30次充放电循环后电极比容量保持率为92.14%,显示了样品电极材料在较大倍率放电条件下较好的结构稳定性和充放电循环寿命。研究La掺杂Zn/Al取代α-Ni(OH)2样品粉体材料的电化学活性效应及其作用机理发现,其电极材料在电极过程的电子转移数分别为1.247e和1.328e,均具有较好的充电接受能力和放电电子转移能力,导电能力和活化性能,比Zn/Al分别一元取代α-Ni(OH)2电极材料相比明显增强。同时,发现稀土元素物质La掺杂可以明显改善电极反应的充放电循环可逆性,并有效抑制镍电极上的析氧反应和降低电极反应的电化学极化和欧姆阻抗,提高其放电电压。更多还原

【Abstract】 This paper summarized the present research situation of the electrode material Ni(OH)2 as positive electrode active material of the MH-Ni battery systemly. Based on the unique electron configuration of rare earth element materials and the 4f electron moving features and some electrochemical functional characteristics of the metal positive ions, through the homogeneous precipitation method with urea, this article studied the technological conditions and the behavior rule of nickel electrode active materialα-Ni(OH)2 prepared by rare earth La doped Zn/Al-substituted. Moreover, the sample material structural features, electrochemical activity and the electrochemical performance were studied. Simultaneously the electrochemical action effect mechanism of the samples as electrode materialα-Ni(OH)2 was discussed.In this paper, we investigated the influence on the performance of electrode material by single factor with the urea content, reaction temperature, reaction time and dispersant. The results show that optimum process conditions of homogeneous precipitation method are that the molar ratio of urea: metal salt is 30:1, the reaction temperature is 90±1℃, and the time of the reaction is 3h, and the drying temperature is 60℃.Zn/Al-substitutedα-Ni(OH)2 samples with doping different La contents were synthesized at optimum processing conditions. The research experimental result indicates that the morphology of samples is the adhesions of numerous sheet and spherical particles with more porous. The microstructure is characterized by the methods such as XRD, Raman, IR, and TG-DSC. The results show that comparing with only Zn/Al-substitutedα-Ni(OH)2, the La doped Zn/Al-substitutedα-nickel hydroxide electrode material have more structure defect and much bigger interlayer distance, and there are much more water molecular and the thermal stability becomes stronger. When the samples power of La doped Zn/Al-substituted were made as the nickel electrode active material, then assembled the MH-Ni simulation battery, the charge/discharge test shows that 5% La doped Zn-substituted sample has a relative high specific capacity (382.85mAh·g-1 at rate of 0.1C), the value of the middle discharge voltage reaches 1.2943V, while the discharge specific capacity reaches 359.85mAh/g at 1.0C and the capacity still remains 91.04% after 30 cycles. In addition, the material electrode of 5% molar ratio La doped Al-substituted sample whose middle discharge voltage 1.2968V is higher, the discharge specific capacity reaches 404.95 mAh/g at 0.1C. And the charge/discharge at the rate of 1.0C test shows that after 30 cycles the capacity still remains 92.14% and it has better structural stability and cycle life at high-rate discharge condition.The research on the electrochemical activity and the electrochemical action effect mechanism of the La doped Zn/Al-substitutedα-nickel hydroxide samples discovery that the number of electrons transferred of the electrode materials are 1.247e and 1.328e in the electrode process, and there are much better charge acceptance and discharge capacity of electron transferred, electrical conductivity and activation performance. Furthermore, the cyclic reversibility of the electrode reaction improves after doping La and the rare earth La has good effect in inhibiting the oxygen evolution reaction of sample electrode, reducing the electrode reaction of the electrochemical polarization and ohmic resistance, and increasing the discharge voltage.更多还原