稀土系AB_5型贮氢电极合金材料优化设计原理

Optimization theory of rare earth-based AB5type hydrogen storage alloys for Ni-MH battery

着重研哭了ＡＢ５型合金中Ａ侧稀土组元的作用，并对合金的各个侧面进行系统的优化研究（Ａ－混吕稀土或纯稀土组元；Ｂ－镍及镍代元素的总称）。贮氢电极合金的电化学性能与其成分、结构和组织密切相关。ＡＢ５型多元电极合金研究过程中，在成分方面，向多元合金化发展，既降低了合金成本，又改善了材料性能；在结构上，合金偏离ＡＢ５结构，发展非化学计量比合金；在显微组织上，从主相向“主相＋辅相”发展，有效地改善了合高倍率放电能力。主要采用多元合金化方法来提高合金的循环寿命和采用混合稀土（Ｍｍ、Ｍｌ、Ｌｍ）代替纯Ｌａ来降低合金成本，以达到实用化的要求。系统地研究子稀土组元ＲＥ＝Ｌａ１－ｘ－ｙ－ｚＣｅｚＮｄｙＰｒｚ对ＲＥ（ＮｉＣｏＭｎＴｉ）５合金电化学性能的影响，为描述稀土组元的综合效应，引入四组元受约束的成分四边形来表达Ｌａ、Ｃｅ、Ｎｄ和Ｐｒ成分变化，在此基础上，作出合金的电化学性能综合图，为筛选稀土组元的最佳组成提供依据。由于纯Ｌａ、Ｃｅ、Ｎｄ和Ｐｒ价格昂贵，工业生产中不宜直接应用以上的研究结果，本研究口进一步采用们廉的富镧混合稀土和富混合稀土按适当比例配制，以获得所需成分要求的合金，基于前面已优化Ａ和Ｂ侧的结果，进一步研究化学计?

The electrochemical properties of metal hydride electrode employing hydrogen storage alloys were determined by the composition , structure and microstructure of hydrogen storage alloys. From econo- my point of view ,the AB5 type electrode material for mass production ,the use of unrefined rare earth mix- ture (mischmetal-Mm. Ml .Lm etc. ) is very effective in lowing its cost. By the optimization of the Ml : Mm ratio ,the alloy Ml0 .85 Mm0.15 (NiCoMnTi)5 showed a maximum capacity of 280mAh/g and good cycling sta- bility. With the compostition of A and B side optimized . the effect of stoichiometric ratio ( value ) on the properties AB type alloys were also studied. The results showed that the discharge capacity of hyper-stoi- chiometric (γ= 5. 3 ) alloy reached 295 mAh/g and its capacity persistence was 85. 6 % after 250 cycles , whereas its high-rate-dischargeability was lower than that of stoichometric alloy (γ=5). The higher capa- city was due to the larger unit cell volume of the alloy with γ=5. 3 , which determined by X-ray diffraction analysis. Non-stoichometric multicomponents hydrogen storage alloys and electrocatalytic intermetallics forming in rare earth-based AB5 type hydrogen storage alloys were developed. Further investigation are inprogress in order to clarify the detailed mechanism.