Microstructure and electrochemical characteristics of nonstoichiometric La-rich AB_5-type alloy for Ni/MH battery electrode

The nonstoichiometric La-rich mischmetal (designated by Ml)-based hydrogen storage alloy with a composition of Ml(Ni0.64Co0.20Mn0.12Al0.04)4.76 was prepared by arc melting and annealed at 1173 K for 10 h to     

新型负极添加剂对MH/Ni电池性能的影响

用过渡金属氧化物作为ＭＨ／Ｎｉ电池的负极添加剂,研究了它对ＭＨ／Ｎｉ电池容量、放电电压、电池内压和循环性能的影响。加人２％的新型负极添加剂,可以在保证电池容量不受影响的前提下,使ＭＨ／Ｎｉ电池的放电中值电压升高约２０ｎＶ,以１Ｃ倍率电流充电时的最大电池内压减少０．４ＭＰＡ,并显著提高电池循环性能。以１Ｃ倍率快速充放测试徨４００次时,其容量保持率在９０％以上,放电中值电压变１．２１６Ｖ。     

Microstructure and electrochemical properties of low-temperature hydrogen storage alloy used in Ni/MH batteries

AB5 hydrogen storage alloys La0.54Ce0.28Pr0.18Ni4-xCo0.6Mno35Alx （x=0.1, 0.2, 0.3） were prepared by arc melting method under an Ar atmosphere. The results show that the contents of Ni and Al have obvious influences on the microstructure and electrochemical properties of the alloys. Both the lattice parameters and the cell volumes decrease with decreasing x value. Moreover, the discharge capacity at different temperatures, the high rate discharge property, and the cycling life of the alloy electrode are also in close relationship with the x value. When x value increases from 0.1 to 0.3, the discharge capacities with a discharge current density of 60 mA/g slightly decreases at 25℃, but evidently deteriorates at -40℃, the high-rate property gravely decreases, and the cycle life of the alloy electrode is improved in some extent. Therefore, it is meaningful to control Al content for the AB5 hydrogen storage alloys used in Ni/MH batteries.     

Electrochemical Properties of the Amorphous Ti3Ni2 Alloy in Ni/MH Batteries

采用机械球磨晶态Ti3Ni2 (Ti2Ni/TiNi)合金的方法制备非晶态的Ti3Ni2合金,并研究其电化学性能.充放电测试结果显示,非晶态Ti3Ni2合金成功地解决了晶态Ti3Ni2合金在高温下(333 K)循环寿命极短的缺点.在333K循环19次后,相对于晶态Ti3Ni2合金较低的容量保持率(39.47％),其非晶态合金有效的将容量保持率提高到88.83％.通过Tafel极化,线性极化以及交流阻抗测试,发现这种改善源于非晶态Ti3Ni2合金的耐蚀性远优于其晶态合金.     

储氢材料的应用与发展

车用镍氢电池性能优良、安全可靠、技术成熟稳定,是混合动力车(HEV)比较理想的辅助动力。随着混合动力车技术的不断发展,动力电池用储氢合金将迎来一个黄金发展期。此外,随着燃料电池技术的日益成熟与发展,以氢气为燃料的电动汽车也将迅速发展起来,这就要求必须有安全高效的贮氢系统与之相匹配。传统的液态及高压气态贮氢方式由于成本、质量、体积大小以及安全性等因素限制,无法应用于车载贮氢系统。相比之下,金属氢化物作为一种新型的能源材料,具有贮氢密度高、安全高效及环境友好等优点,将成为未来车载燃料电池的氢载体。文章主要对近期Ni/MH电池用储氢合金的种类和发展以及高容量镁基储氢材料方面的研究工作做一些综述分析,以期为未来的研究工作提供参考。     

ZrCr2合金对TiV1.1Mn0.9Ni0.5电极合金结构和电化学性能的影响

用两步熔炼法制备TiV1.1Mn0.9Ni0.5-ZrCr2复合电极合金。XRD、EDS、ICP及EIS等分析结果表明：复合合金具有与母体合金相同的双相结构,但是两相的特征参数以及复合合金电极的热力学特性均发生了一系列变化;组分合金在复合过程中产生明显的协同效应;复合合金电极的最大放电容量达到457.2 mAh/g;循环稳定性、荷电保持率和高倍率放电等动力学性能均得到显著改善;1000 mA/g放电电流密度时,复合合金电极的高倍率放电性能是由电极/电解质界面上的电化学反应和合金体内氢的扩散混合控制     

Effect of surface modification of metal hydride electrode on performance of MH/Ni batteries

A novel method was applied to the surface modification of the metal hydride(MH)electrode of MH/Ni batteries.Both sides of the electrode were plated with a thin silver film about 0.1μm thick using vacuum evaporation plating technology,and the effect of the electrode on the performance of MH/Ni batteries was examined.It is found that the surface modification can enhance the electrode conductivity and decrease the battery ohimic resistance.After surface modification,the discharge capacity at 5C(7.5A)is increased by 212 mA.h and the discharge voltage is increased by 0.11 V,the resistance of the batteries is also decreased by 32%.The batteries with modified electrode exhibit satisfactory durability.The remaining capacity of the modified batteries is 89%of the initial capacity even after 500 cycles.The inner pressure of the batteries during overcharging is lowered and the charging efficiency of the batteries is improved.     

硼对稀土系AB5型贮氢合金微观结构及电化学性能的影响

测试分析了稀土系AB5型贮氢合金MmNi3.8Co0.4Mn0.6Al0.2Bx(x=0, 0.1, 0.2, 0.3, 0.4)的微观结构及电化学性能, 研究了硼含量x对贮氢合金电化学性能及微观结构的影响.结果表明, 铸态贮氢合金具有双相组织, 主相为CaCu5型相, 还有少量CeCo4B第二相, 第二相的相丰度随x的增加而增大.对合金进行了不同淬速的快淬处理, 合金中第二相的量随淬速的增加而减少.硼的加入使合金的电化学容量下降, 但活化性能及循环寿命明显提高.特别是对于快淬态合金, 硼对因促进非晶的形成而显著提高循环寿命.     

Al对无钴AB5型贮氢合金微观结构和电化学性能的影响

采用单辊快凝方法制备了过化学计量比稀土贮氢合金La(NiMn)α-xAlx(5<α<6,x为0~0.5),研究了Al含量及淬速对合金电极性能及微观结构的影响。结果表明:快淬过化学计量比合金相结构均为过饱和CaCu5型单相,且随Al含量的增加,合金晶胞体积呈线性增大;不同淬速条件下合金凝固组织的形貌和晶态存在明显差别。随Al含量的增加,合金电极的放电容量有所降低,但电极循环寿命得到极大改善。当x=0.3和淬速为10~15 m/s时,合金电极的最大放电容量为322和309 mA.h/g,经150次循环后,电极容量保持率分别为93.5%和95.5%。低温(400℃)退火对合金电极活化性能有所改善,但并未影响合金的循环寿命。     

正极添加CNTs对MH /Ni电池高倍率性能的影响

对正极中添加多壁碳纳米管(CNTs)的MH／Ni电池的高倍率放电性能进行了研究。结果表明：正极中添加少量CNTs的Ni／MH电池具有优异的高倍率放电性能。利用正极中添加少量CNTs制成的标准AA型电池的内阻在14mΩ左右；在高倍率放电条件下电池有更高的放电平台，3C放电中值电压在1．167V左右，5C放电中值电压在1．108V左右；电池循环容量保持率也高于正极中不加CNTs的电池。随着循环次数的增加，正极中添加少量CNTs的电池内阻升高幅度较小。     

低成本AB5型贮氢合金的研究进展

综述了低成本稀土镍基AB5型贮氢合金的研究进展。分别从合金B侧元素、A侧元素、非化学计量比、制备方法等4个方面进行总结。综合考虑合金成本、成分和性能,可将低成本AB5型贮氢合金分为3类:低钴无钴低成本型、无钴低镍超低成本型、低钴含微量镁低成本高性能即高性价比型。开发低成本AB5型贮氢合金是贮氢合金研究的重要和可持续发展方向之一,相应低成本合金产品占有重要的市场份额。     

Ni/LaNi5多孔复合电极的制备及其析氢电催化性能

先电沉积Ni-Zn合金镀层,然后用浓碱将镀层中的锌脱溶,得到多孔镍,最后采用复合电沉积将LaNi5镶嵌到多孔镍表面,制备成Ni/LaNi5多孔复合电极。采用稳态极化曲线和交流阻抗谱对电极的电催化析氢性能进行了评价,并运用恒电位间歇电解和长时间电解,开路电位等研究了电极的电析氢稳定性。结果表明:Ni/LaNi5多孔复合电极的析氢表观交换电流密度分别是镍和多孔镍的172倍和26倍;多孔复合电极中的LaNi5具有稳定电极的作用,该电极比多孔镍具有更优异的抗断电性能。     

不同Co含量Mm（NiCoMnAl）5贮氢合金的低温放电特性

用电化学方法研究了-40℃条件下Co含量对AB5型贮氢合金的放电容量、氢化物分解的稳定性及氢在贮氢合金中的扩散系数等的影响。结果表明：随Co含量的增大，晶胞体积增大，氢化物分解的焓变增大，低温放电容量减小。氢扩散是影响贮氢合金的低温放电性能的重要因素。     

添加Si对A_2B_7型电极合金结构及电化学贮氢性能的影响(英文)

为改善La–Mg–Ni系A2B7型合金的电化学贮氢性能,在合金中添加一定量的Si元素,通过真空熔炼及退火处理的方法制备La0.8Mg0.2Ni3.3Co0.2Six(x=0-0.2)电极合金。研究Si元素的添加对合金结构及电化学贮氢性能的影响。结果表明,铸态及退火态合金均为多相结构,分别为Ce2Ni7型的(La,Mg)2Ni7相和CaCu5型的LaNi5相以及少量的残余相LaNi3。Si元素的添加没有改变合金的主相,但使得合金中的(La,Mg)2Ni7相减少而LaNi5相增加。添加Si显著地影响了合金的电化学性能。随着Si含量的增加,铸态及退火态合金的放电容量逐步降低,但循环稳定性却随着Si含量的增加而增强。此外,合金电极的高倍率放电性能、极限电流密度、氢扩散系数以及电化学交流阻抗谱的测试均表明合金的电化学动力学性能随着Si含量的增加先增加而后减小。     

铸态及快淬态无钴AB5型贮氢合金的循环稳定性

对AB5型LaxMm1-x(NiMnSiAlFe)49(x=0,0.45,0.75,1.00,摩尔分数)贮氢合金进行了快淬处理,研究了La含量及快淬工艺对合金微观结构及电化学循环稳定性的影响.结果表明:La含量的增加对铸态合金的循环稳定性没有明显影响,但使快淬态合金的循环稳定性下降,且快淬处理能显著提高合金的循环稳定性.当La替代量从0增加到1.00时,经300次充放循环后,铸态合金的容量保持率(Rh)从59.2%增加到59.8%;16 m/s淬速快淬态合金的容量保持率从83.9%下降到65.0%.对于x=0.45的合金,当淬速从0(铸态被定义为淬速等于0)增加到28 m/s时,容量保持率从59.8%增加到75.8%.     

Effects of iron phthalocyanine on performance of MH／Ni battery

Oxygen evolution causes a high inner pressure during charge and overcharge for MH/Ni battery, and an inappropriate eliminating way of the oxygen in the battery results in accumulation of heat. This is the main obstacle to develop and apply high capability and high power battery. How to reduce the ratio of the chemical catalysis rate to the electric catalysis rate in MH/Ni battery is considered as an urgent question. Iron phthalocyanine(FePc) was chosen as an electrochemical catalyst. The batteries were prepared by adding iron phthalocyanine with different dosages. The inner pressure, the capacity attenuation, the discharge voltage and capacity at high current of these three batteries were compared. The battery with 1 mg FePc in the negative electrode exhibits a good performance.     

铸态和快淬态Mm(NiCoMnAl)_5B_x(x=0~0.2)贮氢合金的相结构与电化学性能

用铸造及快淬工艺制备了低钴AB5型Mm(NiCoMnAl)5Bx(x=0~0.2)贮氢合金,测试了合金的微观结构及电化学性能,研究了B含量及快淬工艺的变化对合金晶格常数、热力学参数、微观结构及电化学性能的影响。结果表明:合金的晶格常数、晶胞体积及标准生成焓均随B含量的增加而增大;在一定的淬速范围内,快淬处理可以提高合金的放电容量,但淬速超过某一临界淬速时,快淬合金的容量低于铸态合金;合金的循环寿命随淬速的增加而单调增加。     

La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex合金的相结构和电化学储氢性能（英文）

采用感应熔炼和热处理的方法制备La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75?xFex(x=0~0.20)合金,并研究合金的相结构和电化学储氢性能。全部合金均为单一的具有CaCu5结构的LaNi5相,LaNi5相的晶格常数a和晶胞体积随着x值的增加而增大。最大放电容量随着x值的增加从319.0mA·h/g(x=0)降低到291.9mA·h/g(x=0.20)。在1200mA/g的电流密度下HRD值从53.1%(x=0)降低到44.2%(x=0.20)。合金电极的循环稳定性随着x值的增加而增强,这主要归因于合金抗粉化能力的增强。     

Fe替代Co对AB5型贮氢合金电化学性能和相结构的影响

研究了Fe替代C0对Mm（NiMnSiAl）4.3Co0.6-xFex（x=0，0．2，0．4，0．6）贮氢合金电化学性能和相结构的影响。研究结果表明：Fe替代Co使合金的放电容量降低，但使合金的循环稳定性得到改善；合金具有双相结构，主相为CaCu5型相，还有少量的第二相Ce2Ni7相，随着Fc替代量的增加，第二相没有明显变化，但合金的点阵常数和晶胞体积略有增加，这是Fe替代Co使合金循环稳定性得以改善的一个主要原因。     

Fabrication characteristics and hydrogenation behavior of hydrogen storage alloys for sealed Ni−MH batteries

Hydrogen storage alloys based on LmNi_4.2Co_0.2Mn_0.3Al_0.3 were fabricated to study the equilibrium hydrogen pressure and electrochemical performance. The surface morphology and structure of the alloys were analyzed by SEM and XRD, and then the hydrogenation behaviors of all alloys were evaluated by PCT and electrochemical half-cell. We studied the hydrogenation behavior of the Lm-based alloy with changes in composition elements such as Mn, Al, and Co and investigated the optimal design for Lm-based alloy in a sealed battery system. As a result of studying the hydrogenation characterization of alloys with the substitution elements, hydrogen storage alloys such as LmNi_3.75Co_0.15Mn_0.5Al_0.3 and LmNi_3.5Co_0.5Mn_0.5Al_0.5 were obtained to correspond with the characteristics of a sealed battery with a higher capacity, long life cycle, lower internal pressure, and lower battery cost. The capacity preservation rate of LmNi_3.5Co_0.5Mn_0.5Al_0.5 was greatly improved to 92.7% (255 mAh/g) at 60 cycles, indicating a low equilibrium hydrogen pressure of 0.03 atm in PCT devices.