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1、内蒙古科技大学硕士学位论文 1 摘 要摘 要 随着人们环保意识的加强，移动电子产品的日益小型、轻质化，要求小型高容量Ni/MH 电池配套。众所周知AB5型贮氢合金的容量已接近其理论值，进一步提升空间较小。这就促使开发有更高能量密度的新一代贮氢电极合金。对于提高容量来说，最具希望的合金之一是 La-Mg-Ni 系（PuNi3型）合金，但此类贮氢合金存在的主要问题是电化学循环稳定性较差。因此，开展对此系列合金的系统研究，具有重要的学术价值和良好的应用前景。 本文在国内外 La-Mg-Ni 系贮氢合金研究进展的基础上，确定了以La-Mg-Ni 系贮氢合金作为研究对象，采用 XRD、SEM、电化学测试
2、、动力学测试以及真空快淬工艺、退火工艺技术， 全面系统的研究了元素替代及快淬、 退火等工艺对 La-Mg-Ni 系贮氢合金相结构及电化学性能的影响，得到一些主要结论。 对 La0.75xPrxMg0.25Ni2.9Co0.4Al0.2 (x=0,0.1,0.2,0.3,0.4)系列合金的研究结果表明，随着替代元素 Pr 含量的增加，合金主相由 LaNi3相向 LaNi5相转变。合金最大放电容量、高倍率放电能力、放电电压特性均随着 Pr 含量的增加而降低，但合金的循环稳定性随着 Pr含量的增加稳定增强。Pr 含量 x=0.4 时的合金具有最好的循环稳定性。快淬工艺促进了合金中 LaNi5相的形成
3、，虽然降低了合金容量，但提高了合金的循环稳定性。SEM 分析结果表明合金表面的氧化腐蚀和粉化是导致容量迅速衰退的主要原因。 研究了Zr 替代La 对La0.75xZrxMg0.25Ni2.9Co0.4Al0.2 (x=0,0.05,0.1,0.15,0.2,)系列合金结构与电化学性能的影响。研究发现，Zr 替代 La 后虽然降低了合金的放电容量和放电电压特性， 但合金的高倍率放电性能和循环稳定性得到了大大的改善。 Zr 的替代量为 x=0.2时，合金具有最佳的循环稳定性，x=0.1 时合金具有最佳的高倍率放电性能。快淬促进了合金中出现非晶相，导致合金容量下降而寿命增强。合金表面的氧化腐蚀和粉化
4、是导致容量迅速衰退的主要原因。 对 La0.75Mg0.25Ni3.1-xCo0.4Alx (x=0,0.05,0.1,0.15,0.2)系列合金进行了详细的研究，并采取退火工艺提高其综合性能。结果表明 Al 替代 Ni 虽然降低了合金的高倍率放电性能，但是大幅提高了合金的活化性能和放电电压特性，尤其是合金的循环寿命得到改善。x=0.2 时的合金的具有最佳的循环稳定性。 Al 在合金表面形成一层致密的Al2O3薄膜， 抑制了合金的氧化腐蚀是合金循环稳定性得到改善主要原因。退火工艺有利于 LaNi3相生成和合金组织均匀化，显著提高了合金最大放电容量、放电电压特性和循环寿命。 关键词：贮氢合金；关
5、键词：贮氢合金；La-Mg-Ni 系合金；相结构；电化学性能；元素替代系合金；相结构；电化学性能；元素替代 内蒙古科技大学硕士学位论文 2 Abstract High capacity Ni/MH battery is more and more needed to meet the requirements of advanced and mobile electric appliance. It is well know the AB5 typed alloy, essential part of the most widely used Ni/MH battery, is approac
6、hing its theoretical capacity limit because of its CaCu5 structure. Thus the searching for higher capacity hydrogen storage alloy has remained the task for scientists. Among all the potential new alloys, La-Mg-Ni system alloy is the most promisting candidate. But the main weakness of La-Mg-Ni system
7、 alloy is its poor cycle stability. Therefore, the studying on La-Mg-Ni system alloy holds significant academic value and application potential. In order to improve its cyclic stability, the La-Mg-Ni-Co hydrogen storage alloy was selected as the object of this work based on the review of the researc
8、h and development of the La-Mg-Ni system alloys both from home and abroad. By means of XRD, SEM and electrochemical testing, the influence of element substitution, rapid quenching and annealing treatment on the phase structure and electrochemical properties of alloys were systemically studied to dis
9、cover the relationship between composition, phase structure and edectrochemical properties of alloys. Some important conclusions were obtained. For the La0.75xPrxMg0.25Ni2.9Co0.4Al0.2 (x=0,0.1,0.2,0.3,0.4)alloys, with the increasing of Pr content, the main phases of the alloys transformed from LaNi3
10、 phase to LaNi5 and LaNi2 phases. The maximum discharge capacity, HRD ability and discharge voltage characteristic of the alloys decreased but the cyclic stability of the alloys increased with the increasing Pr content. When x was 0.4, the alloy exhibited the best cyclic stability. The vacuum rapid
11、quenching was in favor of the LaNi5 phase which decreased the maximum discharge capacity but improved cyclic stability.The reason for capacity decay was analyzed and the results showed that the main reasons for capacity degradation of the alloys were pulverization and oxidation during charging-disch
12、arging cycles. Zr was selected as a substitution element for La in La0.75xZrxMg0.25Ni2.9Co0.4Al0.2 (x=0,0.05,0.1,0.15,0.2) alloys and the effects of Zr content x on the structure and electrochemical properties of alloys were investigated in detail. The results showed that the maximum discharge capac
13、ities decreased, but the HRD ability and cycle stability first increased and then decreased with the gradual increasement of Zr content. And the alloy exhibited the best 内蒙古科技大学硕士学位论文 3 cyclic stability and HRD ability when x=0.2 and x=0.1, respectively. Pulverization and oxidation of the alloys dur
14、ing charging-discharging cycles were the main reasons for cycle stability degradation. The La0.75Mg0.25Ni3.1-xCo0.4Alx (x=0,0.05,0.1,0.15,0.2) alloys were researched systemically. The obtained results showed that Al element decreased HRD ability but promoted the activation performance and discharge
15、voltage plateau pressure, especially the cyclic stability. The alloy with x=0.2 Al content exhibited the best cyclic stability. A compact film of Al2O3 was formed on the surface of the alloy, which could reduce the degree of oxidation/corrosion and enhance the cycle stability. The annealing treatmen
16、t was in favor of LaNi3 and microstructure homogenization, resulting in the increasement of maximum discharge capacity, discharge voltage pleatau and cyclic stability. Key Words：Hydrogen storage alloys, La-Mg-Ni alloys, Phase structure, Electrochemcal properties, Element substitution I 独 创 性 说 明独 创 性 说 明 本人郑重声明： 所呈交的论文是我个人在导师指导下进行的研究工作 及取得研究成果。尽我所知，除了文中特别加以标注和致谢的地方外，论 文中不包含其他人已经发表或撰写的研究成果， 也不包含为获得内蒙古科 技大学或其他教育机构的学位或证书所使用过的材料。 与我一同工作的同 志对本研究所做的任何贡献均已在论文中做了明确的说明并表示了谢意。 签名：_ 日期：_
