热处理对La0.65Mg0.35Ni3.0储氢合金电极自放电性能的影响

铸态La0.65Mg0.35Ni3.0储氢合金在1173K热处理后,电极的放电容量、循环稳定性、自放电性能都有明显改善.合金电极的最大放电容量由铸态的350.6mAh·g-1提高到360.7mAh·g-1,室温静置72h后的荷电保持率由铸态的77.7%增加到83.4%.电化学压力-组成-温度(P-C-T)曲线与阳极极化曲线的测试证实了合金电极电化学性能的变化规律.     

烧结温度对TiNi储氢合金电化学性能的影响

采用X射线衍射(XRD)分析,充放电测试,线性极化和电位阶跃等方法研究了在750,850,950℃3个不同温度下进行固相烧结对TiNi储氢合金的相结构和电化学性能的影响。结果表明:随着烧结温度的提高,TiNi合金最大放电容量由179.0 mAh.g-1增加到188.1和211.3 mAh.g-1。虽然温度的升高并没有提高合金的交换电流密度,但却大大增强了氢在合金中的扩散速率,扩散系数D从750℃的2.49×10-10cm2.s-1增加到850℃的2.61×10-10cm2.s-1和950℃的3.48×10-10cm2.s-1,从而显著的改善了合金电极的高倍率放电性能(HRD)。950℃烧结后的合金在1500 mA.g-1的放电电流下仍然可以放出84.6 mAh.g-1的电量。     

A2B7型La0.75Mg0.25Ni3.5-xFex(x=0～0.3)贮氢合金相结构及电化学性能研究

采用感应熔炼方法制备了La0.75Mg0.25Ni3.5-xFex(x=0.0.05,0.1,0.2,0.3)四元贮氢合金,系统地研究了合金B侧Fe对Ni部分替代对合金相结构及电化学性能的影响.X射线衍射(XRD)分析表明,La0.75Mg0.25Ni3.5-xFex由(La,Mg)2Ni7相(包括Gd2Co7型高温相和Ce2Ni7型低温相)组成.此外,随着Fe元素的加入,该类合金中出现CaCu5型LaNi5相,且随着Fe含量的增加而增多.电化学测试表明,随Fe含量的增加,合金电极活化次数变化不大,而其最大放电容量呈现先增后减的趋势,合金的最大放电容量由x=0.05时的376.21 mAh·g -1下降到x=0.3时的340.89 mAh·g-1;合金的高倍率放电性能随着Fe含量的增加而降低,当电流密度为900 mA·g-1时,合金的高倍率放电性能由83.66%(x=0)减小到62.23%(x=0.3);循环稳定性先增加后下降.     

热处理时间对MLNi3.8Co0.75Mn0.4Al0.2合金电化学性能的影响

研究了不同热处理时间对MLNi3.8 Co0.75 Mn0.4 Al0.2储氢合金电化学性能的影响.结果表明,经过不同时间热处理的储氢合金电极高倍率放电性及其放电容量均得到提高,其中经过6 h热处理后的合金电极在900mA/g和1200 mA/g的电流密度下的HRD最高,而原始合金电极在同样的放电条件下却不能放电.     

V2Ti0.5Cr0.5Ni1-xMnx(x=0.05～0.2)储氢合金结构和电化学性能研究

为了研究V基储氢材料的结构和电化学性能,采用真空感应电弧炉熔炼了V_2Ti_(0.5)Cr_(0.5)Ni_(1-x)Mn_x(x=0.05～0.2)储氢合金,并分析该储氢合金电极的微观形貌和电化学性能。结果表明,储氢合金主要由体心立方(BCC)结构的钒基固溶体主相和部分TiNi第二相构成。电化学测试表明,当合金电极中Mn替代Ni的量逐渐增加,储氢合金电极的高倍率放电性能、最大放电容量和交换电流密度逐渐增大,当x=0.2时,合金放电容量最大值为429.3 mAh/g,高倍率放电性能为55%,交换电流密度为52 mA/g,而储氢合金电极的循环稳定性能降低。     

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%。     

高容量LaMgNi贮氢合金的制备与性能研究

利用真空熔炼和真空薄带速凝工艺制备了A2B7型Mm1-xMgx(NiCoAl)3.5(Mm:La,Ce,Pr,Nd)贮氢合金并研究了合金组织结构和电化学特性.SEM分析表明,真空速凝薄片合金有较小的晶粒组成,成分均匀.电化学测试表明,该合金活化性能好,最大放电容量达355.4mAh/g,具有良好的充放电循环稳定性和较好的高倍率充放电能力.利用真空薄带速凝工艺,可生产高容量A2B7型贮氢合金,合金的综合性能接近实用化、产业化的要求.     

Co替代Ni对A2B7型贮氢电极合金相结构及电化学性能的影响

采用感应熔炼方法制备了La0.75Mg0.25Ni3.5-xCox(x=0,0.25,0.75,1)四元贮氢合金,系统地研究了合金B侧Co对Ni部分替代对合金相结构及电化学性能的影响.X衍射(XRD)分析表明,La0.75Mg0.25Ni3.5-xCox由(La,Mg)2Ni-7相(包括Gd2 Co7型高温相和Ce2 Ni7型低温相)组成.此外,随着Co元素的加入,该类合金中出现CaCu5型LaNi5相.电化学测试表明,随Co含量的增加,合金电极活化次数增大,合金电极的最大放电容量增大,合金的最大放电容量由x =0.25时的376.53 mAh/g增加到x=1时的401.62mAh/g,氢扩散系数增大,循环稳定性变差,合金的高倍率放电性能降低,Co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.     

表层涂碳MlNi_(3.93)Co_(0.46)Mn_(0.27)Al_(0.34)/Co_3O_4CeO_2复合贮氢合金电极制备及电化学性能

通过分层涂浆制备表层涂碳的MlNi_(3.93)Co_(0.46)Mn_(0.27)Al_(0.34)/Co_3O_4CeO_2电极,并建立表层涂碳的MlNi_(3.93)Co_(0.46)Mn_(0.27)Al_(0.34)/Co_3O_4CeO_2电极反应机理模型。物理表征结果表明,活性碳(AC)具有高比表面积,为二维结构,贮氢合金呈块状固体,为单相的CaCu5型六方结构;电化学测试结果表明,活性碳形成双电层的同时也作为导电剂在MlNi_(3.93)Co_(0.46)Mn_(0.27)Al_(0.34)/Co_3O_4CeO_2电极表面形成导电网络,可改善贮氢合金电极的电化学性能,在0.2C充放电下,放电比容量292.6mAh·g-1,以1500mAh·g-1倍率放电时,高倍率放电性能(HRD值)为82.5%,循环100次后容量保持率95.91%,在50%DOD下,氢扩散系数及交换电流密度依次为4.7×10-11cm2·s-1,315.6mA·g-1,相比于未涂炭的MlNi_(3.93)Co_(0.46)Mn_(0.27)Al_(0.34)/Co_3O_4CeO_2电极,分别提高了2.4mAh·g-1、20.94%、5.53%、38.2%、34.5%。     

低钴贮氢合金的性能研究及热力学函数测定

利用真空熔炼和真空薄带速凝工艺制备了低钴AB5贮氢合金,并研究了合金组织结构和电化学特性.该合金活化性能好,最大放电容量达337.1mAh/g,具有较好的高倍率充放电能力.采用Sievelts装置测定了PCT曲线及热力学参数,该合金吸氢反应的焓变及熵变值分别为-46.3kJ·mol-1和-120.5J·mol-1·K-1,表明了室温和常压下,这种金属间氢化物都具有较高的稳定性,并且符合作为MH-Ni蓄电池负极材料稳定性的要求.     

Phase Structure and Electrochemical Properties of RE-Mg Based Composite Hydrogen Storage Alloys

Rareearth basedAB5 typealloy ,akindofhy drogenstoragealloyusedasnegativeelectrodemateri alsofthenickel/metalhydride (Ni/MH )secondarybattery ,haseasyinitialactivation ,longcyclelifeandlowcost ,butstillasmalldischargecapacity ,poorhigh ratedischargeability(HRD)andpoorpropertiesatlowtemperature[1,2 ] .Therefore ,howtoincreaseitsdischargecapacityandtoimproveotherelectrochemi calpropertiesismeaningfulbothintheoryandinpracticalapplication .Mg basedhydrogenstorageal loysareremarkablebecauseofitsr…     

Effect of electrolyte concentration on low-temperature electrochemical properties of LaNi5 alloy electrodes at 233 K

The effect of KOH electrolyte concentration on low-temperature electrochemical properties of LaNi5 alloy electrodes at 233 K was studied. The results indicated that the electrolyte concentration had great influence on discharge capacity and discharge voltage plateau of LaNi5 alloy electrode at 233 K, and the highest discharge capacity and discharge voltage plateau were both obtained at 6 mol/L KOH. When the KOH electrolyte concentration changed from 5 to 9 mol/L at 233 K, the high rate discharge ability （HRD） had the same change tendency as the diffusion coefficient, but the exchange current density did not change significantly, which implied that hydrogen diffusion was the control step at low temperature 233 K for discharge process of LaNi5 alloy electrode.     

Effects of annealing on microstructures and electrochemical properties of La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy

The La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy was prepared by induction melting. The structural and morphological characterizations were performed by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical measurements were performed using LAND and CHI 660b electrochemical workstation. The main phases of the alloy were LaNi5 and (La,Mg)Ni3. After annealing, the maximum discharge capacity, cycle stability and high rate dischargeability (HRD) were improved obviously. The maximum discharge capacity reached 373.80 mAh/g (T=1173 K), the C100/Cmax(%) was 72.63% (T=1173 K), and the value of HRD reached 51.8% at a discharge current density of 1150 mA/g (T=1173 K). The cyclic voltammetry (CV) and potentiodynamic polarization were also studied.     

Electrode Characteristics of MmNi_5－type Alloys for Nickel－metal HydrideBatteries

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Application of Nanocrystalline LaNi5-type Hydrogen Absorbing Alloys in Ni-MHx Batteries

Duringlastyears ,interestinthestudyofnanos tructuredmaterialshasbeenincreasing .Thisisduetorecentadvancesinmaterials′synthesesandcharacteri zationtechniquesandtherealizationthatthesemateri alsexhibitmanyinterestingandunexpectedphysicalaswellaschemicalpropertieswithanumberofpoten tialtechnologicalapplications .Forexample ,hydrogenstoragenanomaterialsarethekeytothefutureofthestorageandbatteries/cellsindustries[1,2 ] .TheTiFe ,ZrV2 andLaNi5phasesarefamiliarmaterialswhichabsorblargequantitiesof…     

Effect of carbon coating on electrochemical properties of AB3.5-type La–Y–Ni-based hydrogen storage alloys

The superlattice La–Y–Ni-based hydrogen storage alloys have high discharge capacity and are easy to prepare. However, there is still a gap in commercial applications because of the severe corrosion of the alloys in electrolyte and poor high-rate dischargeability (HRD). Therefore, (LaSmY) (NiMnAl)_3.5 alloy was prepared by magnetic levitation induction melting, and then the alloy was coated with different contents (0.1 wt%–1.0 wt%) of nano-carbons by low-temperature sintering with sucrose as the carbon source in this work. The results show that the cyclic stability and HRD of the alloy first increase and then decrease with the increase of carbon contents. The kinetic results show that the electrocatalytic activity and conductivity of the alloy electrodes can be enhanced by carbon coating. The electrochemical properties of the alloy are the best when the carbon coating content is 0.3 wt%. Compared with the uncoated alloy, the maximum discharge capacity (C_max) improves from 354.5 to 359.0 mAh/g, the capacity retention rate after 300 cycles (S₃₀₀) enhances from 73.15% to 80.01%, and the HRD₁₂₀₀ of the alloy enhances from 74.39% to 74.39%.     

Electrochemical properties of cobalt-free La0.80Mg0.20Ni2.85Al0.11M0.53 （M=Ni, Si, Cr, Cu, Fe） alloys

In order to investigate the effect of different B-site additions on phase structure and electrochemical properties of cobalt-free La-Mg-Ni based alloys, La0.80Mg0.20Ni2.85Al0.11M0.53 (M=Ni, Si, Cr, Cu, Fe) hydrogen storage alloys were prepared and studied systemati-cally. X-ray powder diffraction showed that the alloys consisted mainly of LaNi3 phase and LaNi5 phase except that Cr addition caused a minor Cr phase. Electrochemical testing indicated that alloys with additional Ni, Cr, Cu or Fe were activated within only 1-2 cycles, while that with Si addition needed 4 cycles. Adding Si, Cu and Fe increased cycling stability of La-Mg-Ni based alloys. However, maximum discharge capacity decreased from 362 mAh/g to 215 mAh/g in the order of Ni>Fe>Cu>Cr>Si. In addition, electrochemical kinetics of alloy electrodes was also researched by measuring high rate discharge ability (HRD), hydrogen diffusion coefficient (D) and limiting current density (IL).     

Crystallographic and electrochemical characteristics of La0.7Mg0.3Ni5.5? x (Al0.5Mo0.5) x ( x =0 to 0.8) hydrogen storage alloys

The structure, hydrogen storage property, and electrochemical characteristics of the La_0.7Mg_0.3Ni_5.5−x (Al_0.5Mo_0.5) _x (x=0, 0.2, 0.4, 0.6, 0.8) hydrogen storage alloys have been investigated systematically. It has been found by X-ray powder diffraction and Rietveld analysis that the alloys are multiphase and consist of impurity Ni phase and two main crystallographic phases, namely, the La(La, Mg)₂Ni₉ phase and the LaNi₅ phase, and the lattice parameters and the cell volumes of both the La(La, Mg)₂Ni₉ phase and the LaNi₅ phase increase with increasing Al and Mo content in the alloys. The P-C isotherm curves indicated that the hydrogen storage capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 298.5 (x=0) to 328.3 mAh/g (x=0.6) and then decreases to 304.7 mAh/g (x=0.8). The high rate dischargeability (HRD) of the alloy electrodes increases lineally from 65.4 pct (x=0) to 86.6 pct (x=0.8) at the discharge current density of 1200 mA/g. Moreover, the exchange current density of the alloy electrodes also increases monotonously with increasing x by the linear polarization curves. The hydrogen diffusion coefficient in the alloy bulk, D, increases with increasing Al and Mo content and thus enhances the low-temperature dischargeability (LTD) of the alloy electrodes.     

Co含量对La0.55Pr0.05Nd0.15Mg0.25Ni3.5-xCoxAl0.25（x=0～0.4）储氢合金电极性能的影响

采用电磁感应悬浮炉制备La0.55Pr0.05Nd0.15Mg0.25Ni3.5-xCoxAl0.25(x=0,0.1,0.2,0.3,0.4)系列合金,研究Co含量对合金的相结构、吸放氢性能和电化学性能的影响。研究结果表明,该系列合金主要由LaNi5、Nd2Ni7相组成。当Co含量大于0.2时,合金中出现La2Ni7相。压强-吸氢量-温度(Pressure-Content-Temprature)测试显示在303 K温度下,合金具有良好的吸氢性能,当x=0.4时合金的最大吸氢量为1.29(质量分数,%)。电化学测试表明:随x值变化,合金电极的最大放电容量分别为340.0(x=0.0)、346.6(x=0.1)、370.0(x=0.2)、320.0(x=0.3)和346.6(mA.h)/g(x=0.4);随Co含量增加,合金电极容量保持率不断增加,高倍率放电性能先增加后减小,循环伏安曲线、氢在合金体中的扩散系数D共同反映了合金电极的动力学特性。     

Effect of electrolyte concentration on low-temperature electrochemical properties of LaNi5 alloy electrodes at 233 K

The effect of KOH electrolyte concentration on low-temperature electrochemical properties of LaNi5 alloy electrodes at 233 K was studied. The results indicated that the electrolyte concentration had great influence on discharge capacity and discharge voltage plateau of LaNi5 alloy electrode at 233 K, and the highest discharge capacity and discharge voltage plateau were both obtained at 6 mol/L KOH. When the KOH electrolyte concentration changed from 5 to 9 mol/L at 233 K, the high rate discharge ability (HRD) had the same change tendency as the diffusion coefficient, but the exchange current density did not change significantly, which implied that hydrogen diffusion was the control step at low temperature 233 K for discharge process of LaNi5 alloy electrode.