Structure and Electrochemical Properties of A2B7-Type La-Mg-Ni Hydrogen Storage Alloys

~~Structure and Electrochemical Properties of A_2B_7-Type La-Mg-Ni Hydrogen Storage Alloys     

稀土基AB5型复合贮氢合金的研究进展

制备复合合金是改善贮氢合金性能的一条有效途径。本文对国内外各种多元以及多相稀土复合贮氢材料的研究现状进行了综合评述，主要涉及了AB5-AB2型复合贮氢合金和镁基-AB5型纳米复合贮氢合金的进展。阐述了各种复合材料的组成，微观结构以及电化学性能等，并展望了今后复合贮氢材料的研究方向为应用基础性的研究，如复合作用机制、对热力学性能的影响等方面的研究。     

Electrochemical Properties of Strip Casting LPCNi3.55Co0.75Mn0.4Al0.3 Hydrogen Storage Alloys

LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as-cast) on the electrochemical performances were discussed. It was found that the 0.2 C discharge capacity increased with the increase of the thickness (from 1 mm to 10 mm) of the ingots, mainly due to the enlargement of the unit cell volume; Among the thickness of the ingots in our study, l0 mm sample showed a better activation property; LPCNi3.55Co0.75Mn0.4Al0.3 alloy with 10mm showed higher comprehensive properties than those with other thickness under 1C rate.     

Phase Structure and Electrochemical Properties of Rare Earth Based Hydrogen Storage Alloys

The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this work.Adjusted Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and then to change the phase structure, the influences of phase structure on the electrochemical properties were analyzed.The results indicate that the main phase of all alloys is LaNi5 with CaCu5 type structure and the crystal lattices constants of LaNi5 are changed with increasing x value, i.e, decreased a-axis, increased c-axis and axis ratio and nonlinear decreased crystal volume.The crystal volume of the alloy with x = 0.3 is larger than others.There is second phase A1LaNi4 in alloys when x≥0.3, which decrease the discharge capacity, but increase the cycling stability and high rate discharge ability.Compared comprehensively, the alloy with x = 0.3 shows the higher discharge capacity and the better cycling stability.     

化学计量比对稀土-镁基合金结构和性能的影响

文章研究不同化学计或比的稀土-镁基贮氢合金Mn0.9Mg0.1(NiCoMnAl)5x(x=0.75,0.80,0.85,0.90)相的结构和电化学性能.研究表明,Mn0.9Mg0.1(NiCoMnAl)5x合金的主相均由LaNi5相和LaNi3相组成.但当x≤0.80时,合金中还有LaNi2.28相析出.合金电极的最大放电容量和高倍率性能都随着x值的增大先增加后减少,当x=0.80时,都达到最大值;合金电极在243 K时的放电容量随着x值的增加有显著提高;合金电极的循环稳定性随着x值增大而提高.     

化学计量比对AB5型贮氢合金相结构及电化学性能的影响

对低钴稀土系贮氢合金Ml(Ni0.78Co0.08Al0.06Mn0.08)x(4.8≤x≤5.4)的相结构及电化学性能进行了研究.结果表明在4.8≤x≤5.2的合金中除CaCu5型结构的主相之外,还出现LaNi3第二相,而且合金中第二相(LaNi3)的析出量随着x值的增大而减少,化学计量比x=5.4的合金则有富镍相析出,B侧合金化使低钴贮氢合金形成单相AB5型合金的化学计量比由x=5.0增大至5.2～5.4之间.四种不同化学计量比合金的活化性能都较好,合金的最大放电容量随化学计量比x的增大而增加,过化学计量比(x=5.4)合金具有最大的放电容量,最优的放电电压特性及最佳的循环稳定性,且其高倍率放电性能也较好.     

熔炼法制备的AB5-AB2复合合金的晶体结构和电化学性能

选择AB2 型Laves相合金Zr0 .9Ti0 .1 (Mn0 .35Ni0 .55V0 .1 5) 2 作为添加剂与稀土基AB5型合金进行熔炼处理 ,制备了AB5 AB2 复合合金。XRD表明 ,制备的AB5 AB2 复合合金具有AB5合金的CaCu5主相结构 ,同时含有少量的AB2 合金的C14型Laves相存在。并且 ,随着AB2 含量的增加 ,复合合金中的第二相含量逐渐增加。通过复合处理 ,AB5合金的放电容量、循环寿命和倍率放电性能均得到明显提高。AB5 x ?2 复合合金电极的最大放电容量由x =0时的 3 2 2mAh·g- 1 升高到x =1时的 3 3 1mAh·g- 1 。AB5 1?2 复合合金电极 ,在 15 0 0mA·g- 1电流密度下的放电容量从 62mAh·g- 1 提高到 185mAh·g- 1 ,经 3 0 0次充 /放电循环后的容量保持率从 44 .2 4%提高到 78.5 1%。     

Effects of Strip Casting and Annealing on Electrochemical Properties of LPCNi3.55Co0.75Mn0.4Al0.3 Hydrogen Storage Alloys

The effect of thickness (1～10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-cast alloy with the thickness of 10 nun shows better activation property, higher 1C discharge capacity and better cyclic stability than others.It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloywith the thickness of 3 mm shows much better comprehensive electrochemical properties than as-cast one; The cyclic stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3～6 mm are improved after annealing. It is mainly owing to the great release of intemal stress and the decrease fo the segregation of Mn in the alloys.     

Effect of Annealing on Rare Earth Based Hydrogen Storage Alloys

Rare earth-based hydrogen storage alloy used as negative electrode materials for nickel-metal hydride (Ni-MH) batteries are used commercially.The effect of annealing treatment with different annealing temperature and time on the MLNi3.68 Co0.78 Mn0.35 Al0.27 and MMNi3.55 Co0.75 Mn0.40 Al0.30 alloys were investigated.The crystal microstructure,pressure-composition-isotherms (p-C-T) and electrochemical properties of alloys were examined by X-ray diffraction (XRD), automatic PCI monitoring system and electrical performance testing instruments.The optimum annealing treatment conditions of two kinds of alloys were determined.     

Electrochemical Properties of Silicon Doped MlNi5 Type of Hydrogen Storage Alloys

ＴｈｅＬａＮｉ5 ｂａｓｅｄｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｓａｒｅｐｒｏｍｉｓｉｎｇｎｅｇａｔｉｖｅｅｌｅｃｔｒｏｄｅｍａｔｅｒｉａｌｓｆｏｒｒｅｃｈａｒｇｅａｂｌｅＮｉ/ＭＨｂａｔｔｅｒｉｅｓｂｅｃａｕｓｅｔｈｅｙｐｏｓｓｅｓｓａｈｉｇｈｃａｐａｃｉｔｙａｎｄａｒｅｅａｓｙｔｏａｃｔｉ ｖａｔｅ .ＢｕｔｔｈｅｄｉｓｃｈａｒｇｅｃａｐａｃｉｔｙｏｆｔｈｅＬａＮｉ5ｅｌｅｃｔｒｏｄｅｄｅｃｌｉｎｅｓｒａｐｉｄｌｙｄｕｒｉｎｇｃｈａｒｇｅ ｄｉｓ ｃｈａｒｇｅｃｙｃｌｅｓ (5 0 %ｏｆｔｈｅｃａｐａ…     

Effect of Rapid Quenching on Electrochemical Properties of AB5 and AB3.5-Type Hydrogen Storage Alloys

Effect of rapid quenching on the electrochemical properties of AB5 and AB3.5-type hydrogen storage alloys was studied. The results indicated that the discharge capacities of the rapid quenching MmNi3.55 Co0.75 Mn0.4Al0.3 alloys decrease under 25 and -35℃ with the increase of the quenching rate. Comparatively, the decrease extent of the quenching alloys at -35℃ is lower than that at 25℃. The result on the study of the cycle life indicated that the quenching process was favorable to improve the cycle stabilities of the MmNi3.55Co0.75-Mn0.4Al0.3alloys under 25 and -35℃. Whereas, the effect of the quenching process on the La0.7Mg0.3(Ni0.85Co0.15)3.5 alloy was different at 25℃ from at -35℃. Under 25℃, the cycle life of the alloy was obviously improved by the quenching process, however, the quenching process did not improve but decreased slightly the cycle life at -35℃.     

Hydrogen Absorption Thermodynamic Properties of Rare-Earth Based Hydrogen Storage Alloy in Benzene

Ｔｈｅｐｒｏｐｅｒｔｙｔｈａｔｔｈｅｒａｒｅｅａｒｔｈｂａｓｅｄｈｙ ｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｓｃａｎａｂｓｏｒｂ/ｄｅｓｏｒｂａｌａｒｇｅａｍｏｕｎｔｏｆｈｙｄｒｏｇｅｎａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｈａｓｂｅｅｎｕｓｅｄｓｕｃｃｅｓｓｆｕｌｌｙｆｏｒｈｙｄｒｏｇｅｎｓｅｐａｒａ ｔｉｏｎ ,ｐｕｒｉｆｉｃａｔｉｏｎ ,ａｎｄｔｒａｎｓｐｏｒｔａｔｉｏｎ .Ｉｎｔｈｅａｐｐｌｉｃａｔｉｏｎｓ ,ｉｎｏｒｄｅｒｔｏａｖｏｉｄｐｒｏｂｌｅｍｓｓｕｃｈａｓｔｈｅｏｂｓｔｒｕｃｔｉｏｎｔｏｇａｓ…     

热处理对Ti-Mn基Laves相贮氢合金性能的影响

研究了热处理欠化学计量Ti-Mn基贮氢合金性能及组织结构的影响。研究表明，热处理提高了合金的贮氢量，拓宽了合金P-C-T曲线平台，但增加了平台斜率。通过扫描电镜能谱分析及X射线衍射分析发现，热处理增大了合金相的晶格常数及单胞体积，同时有效地提高了合金成分的均匀性，减少了C15型Laves相在合金中的含量；而热处理后平台斜率的增大可能与合金的价电子/原子比有关。     

镀镍对低钴贮氢合金电化学性能的影响

研究了化学镀镍对低钴贮氢合金粉末颗粒形态和电化学性能的影响。结果表明,镀镍能明显提高低钴贮氢合金的放电容量及循环稳定性,对活化性能亦有改善。SEM分析表明,化学镀镍过程中伴有吸氢反应。分析了镀镍对低钴贮氢合金电化学性能的影响机理。     

热处理对快淬贮氢合金组织和电化学性能的影响

通过XRD、SEM分析和电化学实验,研究了热处理对快淬贮氢合金组织和电化学性能的影响。研究表明,400℃热处理对快淬合金晶粒变化不明显,900℃热处理后合金晶粒明显长大,1100℃热处理使合金部分熔化,随后发生了平衡凝固;900℃热处理后,单胞体积和放电容量均达到最大值,但充放电循环稳定性最差,400℃和1100℃热处理后,放电容量稍有降低,但充放电循环稳定性较好。     

多元低钴稀土基贮氢合金及其电极特性

本文根据多元合金化原则设计了一系列电极用低钴 AB5型贮氢合金。并对其组织、不同温度和不同倍率的电化学性能、P- C- T特性进行了研究。结果表明 ,用多元合金化降低 Co含量后 ,合金的放电容量虽有不同程度的降低 ,但可明显改善其充放电循环稳定性 ,且各种合金在 2 0℃时 1 C和 0 .2 C的放电比率、0 .2 C充放电时 40℃和2 0℃的放电比率均基本保持不变。低 Co合金具有更低的平台压。     

合金的离子半径对镁基储氢材料电化学性能的影响

熔炼法制备了Mg2Ni0.95Al0.05、Mg2Ni0.95Ti0.05、Mg2Ni0.95Sn0.05四种单一元素掺杂镁基储氢电极合金，测定几个主要的电化学性能指标（包括活化循环次数、最大放电容量和容量衰退率），分析不同掺杂元素对合金电化学性能的影响。结果表明，在四种舍金中，舍金的电化学性质随掺杂元素的离子半径有规律的变化。活化性能受离子半径影响较大，最大放电容量与容量衰退率均随掺杂元素离子半径变化出现最佳值。     

球磨时间对MmNi3.9Co0.45Mn0.4Al0.25-CoB复合储氢合金电化学性能的影响

采用机械合金化方法制备MmNi3.9Co0.45Mn0.4Al0.25-CoB复合储氢合金.通过X射线衍射(XRD)分析、扫描电子显微镜(SEM)分析、充放电及线性极化测试.研究了球磨时间对复合储氢合金相结构及电化学性能的影响.研究结果表明:随着球磨时间的增加,复合储氢合金的衍射峰逐渐宽化,杂散衍射峰消失,表现出非晶化趋势;复合储氢合金颗粒尺寸变小,并星球状均匀分布.电化学测试结果表明:当球磨时间达到45 min时,复合储氢合金具有较好的活化及高倍率放电性能,30次循环容量保持卒最高,达到90.66%,表现出良好的电化学动力学性能及催化活性.但当球磨时间过长时,合金颗粒出现相互粘连及团聚的情况,局部出现较大结块,导致复合合金电极的交换电流密度降低.     

Phase Structure and Electrochemical Characteristics of Ml（Ni3.55Co0.75Mn0.40Al0.30）5x （x=0.88, 0.92, 0.96, 1.00） Hydrogen Storage Alloys

The phase structure and electrochemical characteristics of Ml （（Ni3.55Co0.75Mn0.40Al0.30）sx （ x = 0.88, 0.92, 0.96, 1.00） hydrogen storage alloys were studied. The effect of the stoichiometric ratio on the phase structure and electrochemical characteristics was analyzed. The results of XRD reveal that all the alloys consist mainly of LaNi5 phase with the hexagonal CaCu5 structure. But a few of the diffraction peaks of La2Ni7 phase on XRD pattern are observed when x ≤ 0.92, and with decreasing x, the intensity of La2Ni7 diffraction peaks increases and the values of lattice parameters a and cell volume increase, c and c/a of LaNi5 phase decrease gradually. When x≥0.96, La2Ni7 phase disappears and the alloys become single CaCu5-type. The electrochemical tests show that the maximum discharge capacity, high rate dischargeability and low temperature dischargeability are improved to different degrees by adjusting the stoichiometric ratio.     

Effect of Heat-Treatment Process on Properties of Rare Earth Mg-Based System Hydrogen Storage Alloys with AB3-Type

The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed. The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.