【作者】 刘元刚；

【导师】 唐致远；

【作者基本信息】 天津大学 ， 应用化学， 2007， 博士

【摘要】 本论文的工作重点集中于高性能镍氢电池及其新型正极材料的研究。对于高性能镍氢电池,本文以球型β-Ni（OH）₂、AB5型贮氢合金作为正、负极活性材料,成功研制出AA2300mAh高容量镍氢电池,其放电容量2330mAh,具有较高的充放电循环寿命;对比了6种隔膜的物理性能,深入分析了隔膜特性对动力型镍氢电池电化学性能的影响,对镍氢电池用隔膜的评价方法也进行了总结、归纳;研究了LiOH、NaOH、Na₂WO₄等电解液添加剂对镍氢电池电化学性能的影响,发现5wt%Na₂WO₄能够在短期内有效地提高镍氢电池70℃时的放电性能;根据电池爆炸后钢壳的表面及断口形貌,初步探讨了高容量镍氢电池的钢壳爆炸问题,认为钢壳表面镍镀层中的微裂纹、氢脆、充电时H+的迁移以及充电内压p的协同作用是产生电池爆炸的原因。对于新型Ni（OH）₂正极材料,本文采用沉淀转化法制备出微尺度球型Ni（OH）₂,并将其与普通球型Ni（OH）₂以3wt%比例混合后可使镍电极的充电电位降低、放电比容量提高20mAh/g;升高加热温度,以尿素热解产生的NH3·H₂O作为沉淀剂,采用均相沉淀法制备的非掺杂及Al³⁺、Zn²⁺、Mn²⁺、Fe³⁺、Co²⁺、Mg²⁺、Cr³⁺单元掺杂Ni（OH）₂均属于紊态α-Ni（OH）₂结构,晶粒尺寸较小、晶格缺陷较多,均具有较高的电化学循环稳定性;相对而言,Al³⁺掺杂α-Ni（OH）₂的放电平台较高、循环稳定性较好,具有最高的放电容量和充放电效率,其微观结构由纳米级Ni（OH）₂纤维束团聚组成,化学式为Ni_0.70Al_0.18（OH）_1.6（CO₃）_0.1（SO₄）_0.07·（H₂O）_0.6 ;与25℃相比, 60℃时Al³⁺掺杂α-Ni（OH）₂的放电比容量降低10mAh/g,晶型结构稳定性较好,电化学循环95次后仍是晶态α型结构,且具有较高的倍率放电性能。本文首次对固相球磨法制备Ni（OH）₂电极材料进行了全面系统的研究,对比测试了非掺杂及Al³⁺、Zn²⁺、Mn²⁺、Fe³⁺、Co²⁺、Mg²⁺、Cr³⁺单元掺杂球磨Ni（OH）₂的相结构、电化学性能,考察了初始原料中的Ni:Al比例、球磨转速、球磨时间、球料比等工艺因素对Al³⁺掺杂球磨Ni（OH）₂的结构及电化学性能的影响,分析了优化球磨Al³⁺Zn²⁺、Al³⁺Zn²⁺Co²⁺多元掺杂Ni（OH）₂的相结构、热稳定性及其电化学性能。结果表明,采用行星式球磨机对苛性碱、镍盐、金属阳离子添加剂和阴离子稳定剂等直接进行固相球磨,所得产物经去离子水洗涤、离心分离、真空干燥后即可获得在碱液中稳定存在的Ni（OH）₂电极材料;Fe³⁺、Al³⁺掺杂球磨Ni（OH）₂属于紊态α-Ni（OH）₂,空白球磨、Zn²⁺、Mn²⁺、Co²⁺、Mg²⁺、Cr³⁺掺杂球磨Ni（OH）₂属于β-Ni（OH）₂或以β-Ni（OH）₂结构为主;固相球磨Ni（OH）₂电极材料晶粒尺寸较小、结晶度较低、存在较多的晶型缺陷,具有较高的电化学循环寿命和结构稳定性;其中,Al³⁺掺杂球磨α-Ni（OH）₂微观结构由纳米晶纤维束构成,表面团聚现象显著,具有较高的室温电化学性能和60℃放电循环稳定性;与Y₂O₃相比,Na₂WO₄显著提高了60℃时Al³⁺掺杂球磨α-Ni（OH）₂的倍率放电性能;随着初始原料中Al³⁺含量的降低, Al³⁺掺杂球磨Ni（OH）₂经历了α-Ni（OH）₂→α/β-Ni（OH）₂→β-Ni（OH）₂的晶型结构变化,而改变球磨转速、球磨时间、球料比则不会影响Al³⁺掺杂球磨α-Ni（OH）₂的晶型结构;在实验所考察的范围内,Al³⁺掺杂球磨Ni（OH）₂的最佳工艺参数为:初始原料Ni:Al比例5:1、球磨转速200r/min、球磨时间90min、球料比30:1;Al³⁺Zn²⁺、Al³⁺Zn²⁺Co²⁺多元掺杂球磨Ni（OH）₂属于紊态α-Ni（OH）₂结构,与Al³⁺掺杂球磨α-Ni（OH）₂相比,Al³⁺Zn²⁺、Al³⁺Zn²⁺Co²⁺多元掺杂的放电容量降低,循环稳定性提高,活化性能增强。更多还原

【Abstract】 The emphasis of this dissertation was focused on the research of high performance Ni-MH battery and its new positive materials.For the research of high performance Ni-MH battery, one of the findings was that AA2300mAh high capacity Ni-MH battery was successfully manufactured with sphericalβ-Ni（OH）₂ and AB5 hydrogen storage alloy serving as positive and negative materials respectively. The experimental Ni-MH battery could provide a capacity of 2330mAh and preferable cyclic performance. The physical characters of 6 kinds of separators were compared with each other as well as their influence on the electrochemical performance of dynamical Ni-MH batteries. The evaluating methods of Ni-MH separators were also summarized. The effects of electrolyte additives, such as LiOH, NaOH and Na₂WO₄, on the electrochemical performance of Ni-MH batteries were investigated and it was concluded that 5wt%Na₂WO₄ was more effective for improving short-dated electrochemical properties of Ni-MH batteries at 70℃. Based on the surface morphologies and fractographies of exploded steel shell, the explosion problem of high capacity Ni-MH batteries was primarily discussed. It could be generalized that the occurrence of battery explosion could be ascribed to the combined actions of micro-fissures of nickel coating, hydrogen embrittlement, H+ transportation and internal pressure p in the charging process.For the study of new positive materials, smaller size spherical Ni（OH）₂ particles, prepared by precipitation conversion, could reduce the charging potential of nickel electrode and release a capacity of 20mAh/g more than nominal value, when it was mechanically mixed with common spherical Ni（OH）₂ powders at a 3wt% weight ratio. Non-doped and Al³⁺, Zn²⁺, Mn²⁺, Fe³⁺, Co²⁺, Mg²⁺, Cr³⁺ doped Ni（OH）₂ powders were synthesized individually by homogeneous precipitation with a higher heating temperature and NH3·H₂O, generated from the thermal decomposition of urea, as precipitant. All the prepared Ni（OH）₂, which had smaller grain sizes and more lattice defects, belong to turbostraticα-Ni（OH）₂ structure and displayed high electrochemical cyclic stability. Compared with each other, Al³⁺ dopedα-Ni（OH）₂, with a chemical formula of Ni_0.70Al_0.18（OH）_1.6（CO₃）_0.1（SO4）_0.07·（H₂O）_0.6, showed higher discharging plateau and more stable cyclic performance. It had the highest special capacity and charging-discharging efficiency. Its microstructure was composed of agglomerated nanocrystal fibrous bundles. Furthermore, Al³⁺ dopedα-Ni（OH）₂ represented an excellent electrochemical stability, high rate discharging ability at 60℃and a capacity of 10mAh/g lower than that at 25℃. After charged and discharged for 95 cycles, the experimental electrode materials remainedαphase.In this paper, the preparation of Ni（OH）₂ active materials by solid state ball milling method was firstly synthetically studied. The phase structure and electrochemical performance of non-doped and Al³⁺, Zn²⁺, Mn²⁺, Fe³⁺, Co²⁺, Mg²⁺, Cr³⁺ doped Ni（OH）₂ powders were investigated individually. The contributions of Ni:Al ration in the reaction reagents, rotating speed, ball milling periods and ball-mass ratio to the structure and electrochemical properties of Al³⁺ doped Ni（OH）₂ were also researched. Moreover, the phase structure, thermal stability, and electrochemical properties of Al³⁺Zn²⁺, Al³⁺Zn²⁺Co²⁺ multiple doped Ni（OH）₂ synthesized by optimum technique was explored too. The results showed that stable Ni（OH）₂ powders could be made in the following process: directly ball milling the mixture of caustic alkali, nickel salt, metallic ion additive and anion stabilizing agent, and then cleaning, centrifugalizing and vacuum drying the milling products. Non-doped, Zn²⁺, Mn²⁺, Co²⁺, Mg²⁺, Cr³⁺ doped milling products wereβ-Ni（OH）₂ or mainlyβ-Ni（OH）₂, while Fe³⁺, Al³⁺ doped outgrowth belong toα-Ni（OH）₂. Solid state ball milling Ni（OH）₂ had smaller grain sizes, lower crystallinity and more lattice defects. However, they all exhibited high electrochemical cyclic performance and structural stability. The microstructure of Al³⁺ dopedα-Ni（OH）₂ was made up of nanocrystal fibrous bundles with a high agglomerated appearance. It showed a high ambient electrochemical properties and discharging cyclic stability at 60℃. Compared with Y₂O₃, Na₂WO₄ greatly improve 60℃discharge ability of Al³⁺ dopedα-Ni（OH）₂. With the reduction of Al³⁺ content in the starting reagents, the phase structure of Al³⁺ dopedα-Ni（OH）₂ transformed fromα-Ni（OH）₂ toα/β-Ni（OH）₂ and then toβ-Ni（OH）₂. However, rotating speed, ball milling periods and ball-mass ratio would never change the crystal structure of Al³⁺ dopedα-Ni（OH）₂. In the ranges of experimental conditions, the best ball milling technology for Al³⁺ doped Ni（OH）₂ was that a 5:1 ratio of nickel to aluminum in the reactive agents combined with a 200r/min rotating speed, a 90min milling period and 30:1 ball-mass ratio. The Al³⁺Zn²⁺, Al³⁺Zn²⁺Co²⁺ multiple doped outputs were bothα-Ni（OH）₂ structure with a lower capacity, higher cyclic stability, and enhanced activity.更多还原