贮氢合金V3TiNi0.56Al0.2的电化学性能

以NH4VO3、Al等为原料采用自蔓延高温法制备了钒基固溶体型贮氢合金V3TiNi0.56Al0.2,研究了V3TiNi0.56Al0.2贮氢合金的组织结构和电化学性能。结果表明:铸态贮氢合金V3TiNi0.56Al0.2的最大放电容量为350 mA.h/g,活化性能较好,但氢的扩散系数小,循环性能和高倍率放电能力差。合金失去活性的原因是循环过程中钒基固溶体主相不断溶解到电解液中,通过真空熔炼处理可以改善合金的循环性能和高倍率放电性能。     

TiV2.1Nix（x=0.2～0.6）贮氢合金的相结构及电化学性能

系统研究了TiV2.1Nix（x=0．2，0．3，0．4，0．5，0．6）贮氢合金的相结构及电化学性能。XRD及SEM分析表明：合金均由体心立方（bcc）结构的V基固溶体主相和TiNi基第二相组成；随着Ni含量x的增加，合金中V基固溶体主相的相含量和品胞参数逐渐减小，TiNi基第二相含量逐渐增多，且当x≥0．4时，TiNi基第二相组织沿主相晶界形成明显的三维网络状结构。电化学测试表明：随着x的增加，合金的高倍率放电性能及循环稳定性均得到显著改善；但当x从0．4增加到0．6时，合金的活化性能变差，最大放电容量降低。在研究的合金中，TiV2.1Ni0.4表现出较好的综合性能。     

TiV_(2.1)Ni_x(x=0.2~0.6)贮氢合金的相结构及电化学性能

系统研究了TiV2.1Nix(x=0.2,0.3,0.4,0.5,0.6)贮氢合金的相结构及电化学性能。XRD及SEM分析表明:合金均由体心立方(bcc)结构的V基固溶体主相和TiNi基第二相组成;随着Ni含量x的增加,合金中V基固溶体主相的相含量和晶胞参数逐渐减小,TiNi基第二相含量逐渐增多,且当x≥0.4时,TiNi基第二相组织沿主相晶界形成明显的三维网络状结构。电化学测试表明:随着x的增加,合金的高倍率放电性能及循环稳定性均得到显著改善;但当x从0.4增加到0.6时,合金的活化性能变差,最大放电容量降低。在研究的合金中,TiV2.1Ni0.4表现出较好的综合性能。     

RENi4.3—xCoxMn0.4Al0.3贮氢合金（x=0.5—1.3）的相结构及高温电化学性能

系统地研究了Co含量对RENi4.3-xCoxMn0.4Al0.3贮氢合金（x=0.5-1.3)的相结合和高温（60℃）电化学性能的影响。研究结果表明：RENi4.3-xCoxMn0.4Al0.3合金（x=0.5-1.3)具有单一的CaCu5型LaNi5相结构,且其晶胞常数c和晶胞体积V随Co含量的增加而增大,在60摄氏度工作条件下,随Co含量的增加,合金的充放电循环稳定性明显提高,但合金最大放电容量和高倍率放电性能有所降低。     

TiMn2-5x(V4Fe)x(x=0.30, 0.35)贮氢合金结构与性能研究

用XRD、SEM等方法与手段,研究TiMn2-5x(V4Fe)x(x=0.30,0.35)贮氢合金的相结构及电化学性能。结果表明:主相为体心立方(bcc)结构的合金,其晶胞参数随x的增加而增大;SEM显示在基体中存在岛状结构,随着x的增加,岛状结构较基体的比率减少;电化学测试表明,x=0.35合金在常温下难以活化,加热到327K才能活化;而x=0.30合金常温下即可活化,该合金在充电过程中出现钝化,327K温度下钝化消除。比较合金在298K的PCT曲线,发现x=0.30合金的平台氢压约为0.2MPa,平台宽度较大,更有开发价值;同时计算x=0.30合金放氢过程的焓和熵,分别为–36.1kJ/mol,–126.9J/(mol·K)。     

LaNi5-xFex(x=1～1.8)合金相结构及电化学性能

研究了LaNi5-xF3x(x=1.0,1.2,1.4,1.6,1.8)合金中Fe部分代替Ni对LaNi5型电极合金相结构及电化学性能的影响.结果表明:当x=1.0时,合金由LaNi5和La2Ni7相组成;当x=1.2时,开始出现(Fe,Ni)相;当x=1.6时,还开始出现La2Ni3相.随x增大LdNi5相逐渐减少、La2Ni7和(Fe,Ni)相逐渐增多.随Fe含量的增大,电极合金放电容量减小,扩散系数减小,交换电流密度呈先减小后增大的趋势,当x=1.4时,电极合金的交换电流密度达到最小值.Fe含量对合金电极高倍率放电性能HRD值的影响与对合金电极交换电流密度的影响趋势一致,这表明电极合金表面的电化学反应对合金的动力学性能影响更大.     

贮氢合金RENi_(3.95-x)Mn_xCo_(0 .75)Al(0 .3)(x =0～ 0 .6)的相结构与高温电化学性能

针对电动车用大型动力Ni/MH电池工作温度较高的特点 ,系统地研究了Mn部分取代Ni对贮氢合金RENi3 .95-xMnxCo0 .75Al0 .3 相结构和高温 (6 0℃ )电化学性能的影响。结果表明 ,RENi3.95-xMnxCo0 .75Al0 .3(x =0～0 .6 )合金具有单一的CaCu5型LaNi5相结构 ,其晶胞体积随Mn含量的增加而增大 ;Mn的加入能有效地改善合金的高温活化性能和放电容量 ,但会加快合金的循环容量衰退 ,降低充放电循环稳定性 ;Mn含量在x =0 .3～ 0 .5时 ,合金具有较好的高温高倍率放电性能     

贮氢合金RENi3.95-xMnxCo0.75Al0.3(x=0～0.6)的相结构与高温电化学性能

针对电动车用大型动力Ni/MH电池工作温度较高的特点,系统地研究了Mn部分取代Ni对贮氢合金RENi3.95-xMnxCo0.75Al0.3相结构和高温(60     

La0.8-xCexMg0.2Ni3.5(x=0~0.20)贮氢合金电极的低温放电性能

用冷坩埚磁悬浮熔炼炉制各La0.8-xCexMg0.2Ni3.5(x=0.0.05,0.10,0.15,0.20)贮氢电极合金,采用X射线衍射、三电极体系系统研究合金的微观结构和电化学性能.研究表明:合金为多相结构,主相均为Ce2Ni7型六方相,还包括Cacu5型六方相、PuNi3型菱方相;P-C-T曲线显示,随着Ce含最的增加,合金放氢平台区域变窄,平台压力升高.合金中各组成相单胞体积的减小是其主要原因.随着Ce含量的增加,合金常温最大放电容量逐渐减小并且循环稳定性有一定改善;低温最大放电容量则先增大后减小,合金的低温高倍率放电性能以及交换电流密度均随Ce含量的增加而增加,但氢扩散系数随着Ce含量的增加而减小.     

贮氢电极合金Ml（NiMnTi）4.2Co0.8—XFex（x=0—0.8）的电化学性能

详细地研究了Ｍｌ（ＮｉＭｎＴｉ）４．２Ｃｏ０．８－ｘＦｅｘ（ｘ＝０－０．８）合金的电化学性能。试验发现,随着Ｆｅ含量ｘ从０增加至０．,合金的活化性能得到改善,但最大放电容量从３０２ｍＡｈ／ｇ逐渐降低到２８０ｍＡｈ／ｇ,高倍率放电性能从７８．５％缓慢降至７２．５％;当Ｆｅ含量ｘ≤０．４时,合金的自放电率与高Ｃｏ合金（ｘ＝０）相比有所降低,但当Ｆｅ含量ｘ超过０．４后,合金的自放电率较高Ｃｏ合金有所上升     

Structure and electrochemical properties of low-cobalt La1- xLixNi3.2Co0.3Al0.3(0≤x≤0.2) hydrogen storage electrode alloys

The structure and electrochemical properties of a new low cobalt hydrogen storage electrode alloys La1-xLixNi3.2Co0.3Al0.3(0≤ x ≤0.2) were investigated with a different additions of Li in replacement of La. With the increase of Li contents the maximum discharge capacity increases from 240 mAh·g -1 ( x =0) to 328.4 mAh·g -1(x=0.1) and the cycle stability is improved correspondingly. The capacity decay can remaiN28.6% ( x =0.2) after 230 charge/discharge cycles. The high rate discharge(HRD) ability of the alloys( x≤0.1) is improved and the best HRD is 34.1%( x =0.1) under the discharge current density 1200 mA·g -1 . It is found that the prepared alloys are basically composed of LaNi5 as matrix phase and LaNi3 as second phase( x ≤0.1). But the abundance of LaNi3 phase dramatically decreases with increasing x . When x =0.2, a new phase Al(NiCo)3 is formed.     

Phase structures and electrochemical properties of V3TiNi0.56Hf0.24Cox alloys

The phase structures and electrochemical properties of the V₃TiNi_0.56Hf_0.24Co_x alloys have been studied. It is found that the addition of Co into the V₃TiNi_0.56Hf_0.24 alloy decreases the amount of the main phase and increases the amount of the secondary phase. The main phase is a V-based solid solution with b.c.c. structure and the secondary phase is an under-stoichiometric C14-type Laves phase of (Ti, Hf)(V, Co, Ni)_m (m<2) with hexagonal structure. With increasing Co content, the lattice parameters of both the main phase and the secondary phase decrease. This leads to a decreasing stability of the alloy hydride and deterioration in discharge capacity of the alloy electrode. However, increasing Co content improves the durability of the electrodes in KOH solution. In addition, because of the poor reaction kinetics of the Laves phase due to inadequate Ni content, the V₃TiNi_0.56Hf_0.24Co_x alloys show poorer high rate capabilities.     

Structure and electrochemical properties of LaMgNi_(4-x)Co_x(x=0-0.8)hydrogen storage electrode alloys

LaMgNi_(4-x)Co_x(x = 0-0.8) electrode alloys used for MH/Ni batteries were prepared by induction melting. The structures and electrochemical hydrogen storage properties of the alloys were investigated in detail.X-ray diffraction(XRD) and scanning electron microscopy(SEM) analysis show that LaMgNi4 phase and LaNi5 phase are obtained. The lattice parameters of the two phases increase first and then decrease with Co content increasing.The electrochemical properties of the alloy electrodes were measured by means of simulated battery tests. Results show that the addition of Co does not change the discharge voltage plateau of the alloy electrodes. However, the maximum discharge capacity increases from 319.9 mAh·g~(-1)(x = 0)to 347.5 mAh·g~(-1)(x = 0.4) and then decreases to331.7 mAh·g~(-1)(x = 0.8). The effects of Co content on electrochemical kinetics of the alloy electrodes were also performed. The high rate dischargeability(HRD) first increases and then decreases with Co content increasing and reaches the maximum value(95.0 %) when x = 0.4. Test results of the electrochemical impedance spectra(EIS),potentiodynamic polarization curves and constant potential step measurements of the alloy electrodes all demonstrate that when Co content is 0.4 at%, the alloy exhibits the best comprehensive electrochemical properties.     

Effects of rapid quenching on microstructures and electrochemical properties of La_(0.7)Mg_(0.3)Ni_(2.55)Co_(0.45)B_x(x=0-0.2) hydrogen storage alloy

1 Introduction Ni-MH batteries have been used widely by virtue of several of their advantages, such as high capacity, capable of performing a high rate charge/discharge, high resistance to overcharging and over-discharging, a long cycle life, environment…     

Effects of rapid quenching on microstructures and electrochemical properties of La0.7Mg0.3Ni2.55Co0.45Bx（x=O-0.2） hydrogen storage alloy

In order to improve the electrochemical performances of La-Mg-Ni based electrode alloys with PuNi3-type structure, a trace of boron was added in La0.7Mg0.3Ni2.55Co0.45 alloy. The La0.7Mg0.3Ni2.55Co0.45Bx（a=0, 0.05, 0.1, 0.15 and 0.2） alloys were prepared by casting and rapid quenching. The electrochemical performances and microstructures of the as-cast and quenched alloys were investigated. The effects of rapid quenching on the microstructures and electrochemical performances of the above alloys were investigated. The results show that the as-cast and quenched alloys are composed of （La, Mg）Ni3 phase, LaNi5 phase and LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron, and the Ni2B phase in the B-contained alloys nearly disappears after rapid quenching. Rapid quenching increases the amount of the LaNi2 phase in the B-free alloy, but it decreases the amount of the LaNi2 phase in the boron-containing alloys. The effects of rapid quenching on the capacities of the boron-containing and boron-free alloys are different. The capacity of the B-free alloy monotonously decreases with increasing quenching rate, whereas the capacities of the B-contained alloys have a maximum value with the change of the quenching rate. The rapid quenching can improve the stability of La-Mg-Ni based electrode alloy but lowers the discharge plateau voltage and decreases the plateau length. The effect of rapid quenching on the activation capabilities of the alloys was complicated.     

La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0～0.4)贮氢合金的循环稳定性

为了提高La-Mg-Ni系贮氢合金的循环稳定性,以Al部分替代Ni,采铸造及快淬工艺制备了La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0,0.1,0.2,0.3,0.4)电极合金,研究了Al替代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。X射线衍射分析结果表明:铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相、LaNi5相和一定量的LaNi2相;Al替代使铸态合金中LaNi2相的量显著增加,但对快淬态合金中LaNi2相的相丰度影响不显著。电化学测试结果表明:随Al替代量的增加,合金的循环寿命大幅度提高;快淬处理可以提高合金的循环寿命,但随Al替代量的增加,淬速对循环寿命的影响减小。     

Microstructure and electrochemical properties of La_(0.8-x)MM_xMg_(0.2)Ni_(3.1)Co_(0.3)Al_(0.1)(x=0,0.1,0.2,0.3)alloys

The present study aims to improve electrochemical properties of the La-Mg-Ni-based hydrogen storage alloys through partial substitution for La by mischmetal(MM).The La_(0.8-x)MM_xMg_(0.2)Ni_(3.1)Co_(0.3)Al_(0.1)(x=0,0.1,0.2,0.3)alloys were prepared by inductive melting,and their phase structures and electrochemical properties were studied by X-ray diffraction(XRD),scanning electron microscope(SEM),energy-dispersive X-ray spectrometry(EDX)and electrochemical tests.Results show that the alloys mainly consist of La_2Ni_7-type phase,La_5Ni_(19)-type phase,LaNi_5-type phase and LaNi_3-type phase.The addition of MM does not change the phase compositions,while it leads to more uniform phase distribution and obviously promotes the formation of La_2Ni_7-type phase which possesses favorable electrochemical properties.Electrochemical studies indicate that the substitution for La by MM could effectively improve the high rate dischargeability(HRD)of the alloy electrode,and the optimal value of HRD_(1500)(HRD at 1500 mA·g~(-1))increases from 40.63%(x=0)to 60.55%(x=0.3).Although the activation properties of the alloy electrodes keep almost unchanged,both the maximum discharge capacity(C_(max))and the cycling stability are significantly improved by MM addition.     

La(1-x)MgxNi4.25Al0.75(x=0-0.3)合金的结构与储氢性能研究

采用三步感应熔炼法制备了La(1-x)MgxNi4.25Al0.75 (x=0.0,0.1,0.2,0.3) 储氢合金,对该系列合金的晶体结构和储氢性能方面进行了研究。晶体结构和相分析结果表明,当x=0.0和0.1时,合金由单一的LaNi4Al相组成;而x=0.2和0.3时,合金由LaNi4Al相, (La,Mg)Ni3相和AlNi3相构成。随着Mg含量x从0.2增至0.3时,合金的第二相丰度和吸/放氢平衡压明显升高,同时储氢容量减小。研究发现,当Mg添加量x=0.1时,合金除具有良好的储氢容量和低平台压外,其吸氢动力学性能更好。     

铸态La1-xSmxMg3.6Co0.4 (x = 0-0.4)合金的贮氢性能研究

采用真空感应熔炼方法制备了La1-xSmxMgNi3.6Co0.4 (x = 0-0.4)合金,并系统研究了Sm替代La对合金相结构、形貌、以及贮氢性能的影响。XRD和SEM分析了合金的相结构,结果表明合金包含LaMgNi4和 LaNi5两相。La1-xSmxMgNi3.6Co0.4 (x = 0-0.4)系列合金在348K,3MPa下的气态吸氢量随着Sm添加呈现逐渐降低的趋势,分别为1.859、 1.707、1.585、1.578、1.471 wt.%。合金的P-C-T曲线显示LaMgNi4相在吸放氢时有平坦的平台压,同时通过在323 K,348 K,373K下对合金P-C-T曲线的研究表明,La1-xSmxMgNi3.6Co0.4 (x = 0-0.4)合金中LaMgNi4相在吸氢过程中的焓变在x = 0时的为-40.37 kJ/mol,随着Sm替代量增加到x = 0.4,焓变降到了-26.99 kJ/mol。而熵变也从x = 0时的-101.9 J/mol/K降到了x = 0.4时的-77.56 J/mol/K。La1-xSmxMgNi3.6Co0.4 (x = 0-0.4)合金的电化学合金测试表明,最大放电容量随着Sm替代量的增加从347 mAh/g降到了270.5 mAh/g,但是合金的循环稳定性随着Sm替代的增加得到了很大的提高。