AB5-type Alloys Research Articles

The influence of trihaloacetic acids on the hydrogen sorption properties of palladium nanoparticles-modified AB5 alloy in aprotic ionic liquid: Towards ionic liquid-based electrolytes for hydride batteries

Binary mixtures of acetic acid/trihaloacetic acids with aprotic ionic liquid – 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MS]) are used as electrolytes for hydrogen electrosorption measurements. Preliminary studies are performed with palladium limited volume electrode to determine optimum concentration of the acid additives for hydrogen capacity and physicochemical properties of the electrolytes. The results obtained for trichloro- and tribromoacetic acid indicate that their decarboxylation occurs after mixing with [EMIM][MS] and dissolution of palladium is observed in contact with the decomposed electrolyte. Research on hydrogen capacity of palladium nanoparticles-modified AB5-type alloy is performed in mixtures of acetic acid and trifluoroacetic acid of optimum concentration. The best electrochemical performance is demonstrated by 2 M acetic acid/[EMIM][MS] mixture. The determined value of specific capacity of the investigated hydrogen absorbing material reaches 230 mAh g−1 and is close to that previously obtained from aqueous solutions of acids or bases.

Function mechanism of Fe in improving cycle stability and plateau characteristics of AB5-type hydrogen storage alloys

Rare-earth AB5-type alloys have great application potential in solid-state hydrogen storage. To further improve their plateau characteristics and cycling life, the effects of Fe on the long-term hydrogen storage properties of LaNi5-xFex (x = 0, 0.5, 1) alloys are studied, and the function mechanisms are revealed. Fe induces a (Fe,Ni) phase layer with good ductility around LaNi5 main phase, which plays a buffer role to relieve the microstrain during hydrogen absorption/desorption, thus stabilizing the crystal structure and improving the cycling performance. Further, Fe with larger atomic radius than Ni relieves the compression from 12o to 6 m site of the LaNi5 phase, and suppresses the plateau splitting phenomenon, resulting in a single and long hydrogen absorption/desorption plateau throughout 1000 cycles. This study promotes the understanding and application of cheap and effective Fe in improving the hydrogen storage properties of AB5-type alloys during long-term cycling.

Activation of long-time placed TiMn-based AB2-type alloy by co-doping of LaNi5 and V for hydrogen storage

TiMn-based AB2-type hydrogen storage alloy with low cost, relatively suitable platform pressure, and high hydrogen storage capacity, stands out as one of the most promising candidates for practical applications in hydrogen storage. However, the TiMn-based alloy gradually losses activity, especially during prolonged exposure to air, posing challenges for activation and greatly increasing the operation cost in large-scale application. The LaNi5 alloy exhibits excellent initial activation performance, making it an ideal additive to enhance the initial reaction kinetics of TiMn-based AB2-type alloy. Nevertheless, the introduction of LaNi5 tends to reduce the hydrogen storage capacity of the mother alloy. Vanadium (V) possesses a relatively high hydrogen storage capacity (3.8 wt.%), and its addition can enhance the hydrogen storage capacity of the mother alloy. In this study, we employ a co-doping strategy, using 5 wt.% of LaNi5 and 5 wt.% of V, to activate an inactive TiMn-based AB2-type alloy (placed for 1 year in air). This approach not only enhances the initial reactivity of the TiMn-based mother alloy but also restores its high-capacity performance. At 303 K and 6 MPa H2 pressure, the co-doping alloy (90 wt.% TiMn-based alloy - 5 wt.% LaNi5 - 5 wt.% V) demonstrates a substantial increase in initial hydrogen absorption rate, achieving a hydrogen absorption capacity of 1.61 wt.% in 6 min. The maximum hydrogen absorption capacity reaches 2.00 wt.% in 90 min. After 5 and 20 cycles, it maintains a reversible capacity of 1.55 and 1.45 wt.%, respectively. The outstanding hydrogen storage performance is attributed to the formation of multiphase alloys, as evidenced by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) measurements. The reaction enthalpy (ΔH) of the co-doping alloy is calculated as 34.1 kJ/(mol H2), a value suitable for operation at room temperature. This work supplies an efficient strategy for the activation of long-time placed inactive hydrogen storage alloys and the enhancement of their hydrogen storage performance, and avoids the waste of raw materials due to inactivation in air. The achievements shed lights on the regeneration of inactive alloys and the cost control in the case of large-scale application of solid hydrogen storage alloys.

Structures and electrochemical performances of La0.7Sm0.3MgNi3·6Co0.4 + xwt.%Ni (x = 0,5,10,15,20) alloys applied to Ni-MH battery

The La–Mg–Ni–Co-based AB2-type alloys, namely La0.7Sm0.3MgNi3·6Co0.4xwt.%Ni (x = 0,5,10, 15, 20), were synthesized through ball milling. The study focused on investigating the impact of Ni content on the structures and electrochemical properties. The structures of the samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscope (TEM). It has been demonstrated that the experimental samples consist of a primary phase, LaMgNi4, and a secondary phase, LaNi5. The abundance of phases undergoes significant changes with variations in Ni content, while the phase composition remains constant. The results indicate that a rise in Ni concentration results in an elevation of the LaNi5 phase and a reduction of the LaMgNi4 phase. Additionally, ball milling and the addition of nickel contribute to the refinement of the alloy grains. As the nickel concentration reached 20 wt%, the cycle retention rate(S30) of the composite alloy electrode achieved its maximum value of 73.42 %. In addition, the electrochemical kinetic test findings demonstrated that the maximum D value of the hydrogen diffusion system was 1.807 × 10−10 cm2/s and that the maximum current density of the composite hydrogen storage alloy electrode was 723 mA/g when x = 0 wt%.

Development and optimization of a two-stage metal hydride hydrogen compressor with AB2-type alloys

This study reports the development of a two-stage metal hydride hydrogen compressor (MHHC) capable of compressing hydrogen from 1 to 30 MPa through a temperature change between 20 and 150 °C. AB2-type hydrogen storage alloys in the C14 Laves phase are employed, where A = Ti and Zr and B = Cr, Mn, and V. The pressure transfer conditions between the two stages are investigated, and the composition of the AB2 alloys is optimized accordingly: the Mn content x in Ti0.8Zr0.2Cr1.9−xMnxV0.1 and the Zr content y in Ti1−yZryCr1.2Mn0.8, for the 1st and the 2nd stage materials, respectively. A laboratory-scale two-stage compressor is fabricated and operated using the selected alloys, whereby hydrogen is successfully compressed to 30 MPa. The compression capacity is analyzed to estimate the useable capacity of the materials. The results of this study can serve as a guide for the design and evaluation of multistage MHHCs.

Novel temperature-driven technique to characterize hydrogen sorption properties under vacuum conditions: Method development, experimental setup, and demonstration on the AB5-type metal hydride LaNi4.1Al0.52Mn0.38

In this study, a modified temperature-controlled sorption characterization technique based on a Sieverts’ apparatus is presented. The main characteristic of the developed method is the hydrogen mass being constant in the system over individual measurement runs while the thermochemical reaction is controlled by the sample temperature. This allows the sorption properties to be measured in vacuum – even down to high vacuum - without the need for large capturing volumes provided. The method itself, the correspondingly built test rig as well as the measurement procedure are discussed in detail. Sources of uncertainty are discussed and evaluated.By performing reference measurements of the absorption and desorption equilibria of the AB5-type alloy LaNi4.1Al0.52Mn0.38, the method is validated and the corresponding results are demonstrated for the first time. Extensive measurements are performed and complete pressure-composition-isotherms are presented along with repeat measurements series to confirm the results of the novel technique. The obtained PCI data are compared with pressure-concentration isotherms from the literature to validate the measurement method and system. The primary equilibrium data in this work are in very good agreement with both the repeat measurements and the comparison with literature data. It can be shown that the method as well as the experimental design are valid and capable of providing accurate measurements of hydrogen sorption behavior.

Composition design of (LaCeCa)1(NiMnAl)5 alloys by uniform design method and their hydrogen storage performance

Rare-earth-based AB5-type alloys are strong candidates for use in solid state hydrogen storage applications; however, their capacity needs to be improved. To efficiently optimize the hydrogen storage performance of AB5-type alloys, the effects of the substitution of Ce and Ca for La (A side) and Mn and Al for Ni (B side) on the structural properties and hydrogenation/dehydrogenation performance of the (LaCeCa)1(NiMnAl)5 alloy series were studied systematically using the uniform design method. X-ray diffraction analysis and scanning electron microscopy showed that all the designed alloys consisted of a single uniform LaNi5 phase. The atomic radii and contents of the constituent elements had a determining effect on the cell volume and properties of the alloys. The maximum hydrogen storage capacity of the (LaCeCa)1(NiMnAl)5 alloy series is approximately 1.7 wt%, which is much higher than the theoretical hydrogen storage capacity of LaNi5 (1.39 wt%).

Effects of Cu doping on the hydrogen storage performance of Ti-Mn-based, AB2-type alloys

The Ti-Mn-based AB2-type hydrogen storage alloy has been widely researched and applied because of their higher hydrogen storage capacity, appropriate service temperature and low cost. However, before this hydrogen storage material becomes a mature technology, the essential issues of activation difficulty and high plateau pressure in hydrogen absorption/desorption process, need to be completely reformed by radical transformation in composition design and structure optimization. This work investigates the microstructure and hydrogen storage performances of Ti0.8Zr0.2Mn0.92Cr0.87Fe0.21 + x Cu (x = 0, 3, 5 and 8 wt%) by vacuum arc melting. Profiting from the excellent hydrogen transfer rate and structure optimization, the Ti0.8Zr0.2Mn0.92Cr0.87Fe0.21 alloys with the increasing of Cu doping result in the unique C14 Laves phase with the increased lattice volume. As a beneficial result, the decrease of the hydrogen absorption platform of Ti0.8Zr0.2Mn0.92Cr0.87Fe0.21 + 8 wt% Cu alloy is accompanied by the increase of the hydrogen desorption platform, thereby reducing the overall hysteresis coefficient of the material. Through Van't Hoff thermodynamic calculation results, it is found that the absolute values of hydrogenation enthalpy and entropy increase with the increasing of Cu doping. It is crucial to doping Cu inside the alloy by the accurate control of stoichiometric proportion and Cu content, which can improve the hydrogen storage performance of the alloy through theoretical analysis and First-principles simulation. This attempt enables new insights into the optimization of the hydrogen storage properties of Ti-Mn-based AB2-type hydrogen storage alloy, which can be generalized to the design of other new hydrogen storage materials.

Effect of SiO2-doped on microstructural evolution and hydrogen storage performances of AB2 type alloy

The influence of impurities (such as Si, O) on the properties of hydrogen storage alloys in industrial processes received extensive attention, yet the role of Si and O coexisting on the hydrogen absorption and desorption properties of AB2-type hydrogen storage alloys remains to be clarified. We investigated the doping of SiO2 on the microstructure and hydrogen storage properties of Ti-Mn based AB2-type hydrogen storage alloy. When a small amount of SiO2 (<1.0 wt%) was added, the hydrogen storage properties of the alloy did not change much and still maintained excellent cyclic stability, and the only difference was the plateau pressure of the alloys doped with SiO2 decreased. However, when excessive SiO2 (∼2.0 wt%) was added, the hydrogen storage plateau slope of the alloy increased sharply, and the hydrogen storage capacity decreased. It is ascribed that the formation of ZrO2 phase and the doping of Si with the SiO2 content increase, resulting in the lattice constant of the alloy increasing and the plateau pressure decreasing. These findings hold promising reference prospects for practical production.

New insights into the electrochemical and thermodynamic properties of AB-type ZrNi hydrogen storage alloys by native defects and H-doping: Computational experiments

In this study, we perform a computational experiment to inspect the impact of native Zr/Ni defects and H-doping atoms on the electrochemical and thermodynamic properties of the AB-type ZrNi alloys. The Korringa-Kohn-Rostoker (KKR) method integrated with the coherent potential approximation (CPA) was employed to execute the calculations. The results revealed that native Zr/Ni defects and hydrogen doping have a beneficial effect on the hydrogen storage properties of the studied compounds by decreasing the stability and decomposition temperature. In particular, we find that with an optimal concentration of native Zr/Ni defects and H-doping, the obtained values of the decomposition temperature are in accordance with the required values for the practical use of nickel-metal hydride (Ni-MH) batteries as a negative electrodes (253 to 318 K) as well as powering proton exchange membrane (PEM) fuel cells (289 to 393 K). Using the density of states (DOS), this decrease can be explained by the diminution of the number of Zr and Ni atoms that establish strong bonds with H atoms and by the shift of the total DOS toward the higher energies. The electrochemical capacity of Zr1-x-yNiH3+y and ZrNi1-x-yH3+y compounds increases to reach values of 550 and 540 mAh/g, respectively. These values are almost twice higher compared to the compounds currently used in the market based on the AB5-type alloy LaNi5 (300 mAh/g). These findings of enhanced electrochemical and thermodynamic properties could provide useful clues for the development of better ZrNi-based materials for Ni-MH batteries, PEM fuel cells and other related areas.

Influence of element substitution on structural stability and hydrogen storage performance: A theoretical and experimental study on TiCr2-xMnx alloy

AB2-type alloys have been widely used for metal hydride hydrogen compressors and hydrogen storage systems. The crystal structure and hydrogen storage properties mostly rely on their composition and atomic distribution. Thus, revealing the relationship between structure and properties can lead to the design of alloys with optimized properties for hydrogen storage application. Here, the structure stability, bonding energy, thermodynamic and kinetic properties of TiCr2-xMnx (x = 0, 0.25, 0.5, 0.75, 1) alloy/hydride have been firstly investigated by combining density functional theory calculation and experiment. It demonstrates that Mn-doped TiCr2 alloy has a stable C14 phase, and Mn can optionally substitute for Cr sites. Additionally, with increase of Mn content, the desorption plateau increases and the ΔH value decreases. In particular, the ΔH values of TiCr2-xMnx hydrides are consistent with the heat released when H atoms occupy the interstitial interstices. Finally, the hydrogen absorption kinetics simulation shows that Mn is unfavorable to the hydrogen absorption kinetics, in which TiCrMn is 124 s longer than TiCr2 when 90% hydrogen-absorption capacity is reached. The relationship between calculations and experiments presents here can be used as a reference for subsequent screening of alloying elements with high melting point and cost for metal hydride system.

Enhanced cycling stability and reduced hysteresis of AB5-type hydrogen storage alloys by partial substitution of Sn for Ni

Rare-earth AB5-type alloys have been widely studied due to their great application potential in gaseous hydrogen storage, but their overall hydrogen storage properties still need to be further improved for more extensive applications. In this work, the effect of Sn partial substitution for Ni on the plateau characteristics and cycling performance of the LaNi5-xSnx (x = 0, 0.25, 0.5, 0.75, 1) alloys are systematically studied. It is found that the segregation effect caused by Sn addition leads to the multi-CaCu5 phase structure with different cell parameters which may have a positive effect on stabilizing the alloys’ structure during cycling by playing a buffer role. Also, the replacement of Sn element results in a higher anisotropic c/a value, which reduces microstrain and improves the cycle life. The capacity retention after 1000 cycles increases from 83.2% (x = 0) to 95.8% (x = 0.75). Moreover, the addition of Sn significantly reduces the hysteresis of the alloys from 0.212 (x = 0) to 0.023 (x = 0.5) at 383 K, owing to the reduction of the microstrain during hydrogen absorption/desorption.

The catalytic oxidation properties for BH4− and electrochemical properties of the Ag-decorated AB5-type hydrogen storage alloy

Anode catalysts for direct borohydride fuel cells (DBFCs) are one of the key factors controlling the performance of such cells. Hydrogen storage alloys are efficient and inexpensive DBFC anode catalysts. However, when hydrogen storage alloys are used as DBFC anode catalysts, their catalytic oxidation capacity is weakened due to their easy passivation in alkaline electrolytes. In order to improve the catalytic oxidation ability of AB5-type hydrogen storage alloy, Ag-decorated AB5-type alloy catalysts with different Ag contents were prepared by vibration ball milling method in this study. The microstructures, catalytic properties on BH4− and electrochemical properties of pure Ag, AB5-type and Ag-decorated AB5-type alloy samples were studied in detail. The results show that the Ag-decorated AB5-type alloys are composed of a single LaNi5 phase. Some of Ag powders cover the surface of the AB5-type alloy particles. Among the Ag-decorated AB5-type alloys, the Ag-decorated AB5-type alloy with an Ag content of 2 wt.% exhibits the best electrochemical performance and catalytic performance for BH4−. Its maximum discharge time in 6 M KOH solution is 303 min, which is 43 min longer than that of the AB5-type alloy. The number of electrons transferred by the Ag-decorated AB5-type alloy with 2 wt.% is the largest, reaching 1.45. The improvement of the electrochemical and catalytic properties of the alloy is mainly attributed to the proper Ag powders coating on the surface of the AB5-type alloy particles, which protects the electrode from oxidation and corrosion, and enhances the conductivity of the alloy electrode.

Optimizing Ti–Zr–Cr–Mn–Ni–V alloys for hybrid hydrogen storage tank of fuel cell bicycle

AB2-type Ti-based alloys with Laves phase have advantages over other kinds of hydrogen storage intermetallics in terms of hydrogen sorption kinetics, capacity, and reversibility. In this work, Ti–Zr–Cr-based alloys with progressive Mn, Ni, and V substitutions are developed for reversible hydrogen storage under ambient conditions (1–40 atm, 273–333 K). The optimized alloy (Ti0.8Zr0.2)1.1Mn1.2Cr0.55Ni0.2V0.05 delivers a hydrogen storage capacity of 1.82 wt%, the hydrogenation pressure of 10.88 atm, and hydrogen dissociation pressure of 4.31 atm at 298 K. In addition, fast hydrogen sorption kinetics and low hydriding-dehydriding plateau slope render this alloy suitable for use in hybrid hydrogen tank of fuel cell bicycles.

Heat and mass transfer in a metal hydride reactor: combining experiments and mathematical modelling

Heat transfer in porous metal hydride (MH) beds determines efficiency of MH devices. We present a COMSOL Multiphysics numerical model and experimental investigation of heat and mass transfer in a MH reactor filled with 4.69 kg of AB5 type alloy (Mm0.8La0.2Ni4.1Fe0.8Al0.1). To achieve an agreement between the model and experiments it is necessary to include a flow control device (inlet valve or flow regulator) into the model. We propose a simplified and easy-to-calculate boundary condition based on a porous domain with variable permeability at reactor inlet. The permeability of the domain is connected with hydrogen mass flow by a PID controller. Thus, boundary conditions for the inlet pressure and mass flow are coupled and heat transfer inside the reactor could be calculated without additional assumptions applied to heat and mass transfer in the MH bed.

Effects of Ti substitution for Zr on the electrochemical characteristics and structure of AB2-type Laves-phase alloys as metal hydride anodes

The structural composition and electrochemical capacity of four AB2 Laves-type intermetallic alloys with various Ti/Zr ratios (TixZr1−xLa0.03Ni1.2Mn0.7V0.12Fe0.12, x = 0.12, 0.15, 0.18, and 0.22) were investigated in this study. The alloys were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. These data revealed the coexistence of the main phase of the C15-type FCC Laves-type AB2 compounds with a secondary La–Ni intermetallic that was present in minor amounts. Increasing the Ti substitution for Zr caused the gradual shrinkage of the unit cells of the C15 phase. The neutron powder diffraction studies demonstrated that in the trihydride (Ti, Zr, V)(Ni, Mn, Fe, V)2D3.2, D atoms filled A2B2 tetrahedra, whereas V atoms occupied not only conventional 16d sites but also partially replaced Zr/Ti at 8a sites. All studied alloys showed similar activation behaviors, wherein four cycles were required to realize the highest electrochemical capacity of the anodes. The Ti12/Zr88 alloy demonstrated excellent full discharge capacity that reached 466 mAh/g. The Ti22/Zr78 alloy electrode exhibited good cycling stability (retention rate of ~71%) after 500 cycles and a superior high-rate discharge capability (retention rate of ~71%) at a discharge current density of 400 mA/g. The cycling of the Ti22/Zr78 alloy electrode was studied by electrochemical impedance spectroscopy (EIS) to understand the reasons for the deterioration of cycling capacity, which was related with the pulverization of the alloys and increase in irreversible capacity.

Influence of over-stoichiometry on hydrogen storage and electrochemical properties of Sm-doped low-Co AB5-type alloys as negative electrode materials in nickel-metal hydride batteries

The La0.582Ce0.191Zr0.025Sm0.202(Ni0.849Co0.032Mn0.05Al0.069)5+x (x = 0.00, 0.10, 0.20, 0.35 or 0.47) hydrogen storage alloys are firstly synthesized to explore the influence of over-stoichiometry on crystal structure and electrochemical performance for nickel-metal hydride (Ni-MH) battery anodes. These alloys possess major CaCu5-type AB5 and minor BiF3-type Ni2MnAl phases. The decreasing of cell volume and charge acceptance ability of the alloy electrodes reduces capacity and peak power density. Meanwhile, the decreasing of MH stability results in the poorer charge retention rate. The enhanced anti-pulverization property of larger anisotropic factor (c/a) and the weakened electrode polarization promote the cycle stability. Moreover, the higher discharge plateau potential is beneficial to the discharge capacity at − 20 and − 40 °C. The high rate discharge ability (HRD) and initial voltage drop decrease at first and then increase because of the changing rate-determining factor of HRD with the shifted x.

Reversible hydrogenation of AB2-type Zr–Mg–Ni–V based hydrogen storage alloys

The development of hydrogen energy is hindered by the lack of high-efficiency hydrogen storage materials. To explore new high-capacity hydrogen storage alloys, reversible hydrogen storage in AB2-type alloy is realized by using A or B-side elemental substitution. The substitution of small atomic-radius element Zr and Mg on A-side of YNi2 and partial substitution of large atomic-radius element V on B-side of YNi2 alloy was investigated in this study. The obtained ZrMgNi4, ZrMgNi3V, and ZrMgNi2V2 alloys remained single Laves phase structure at as-annealed, hydrogenated and dehydrogenated states, indicating that the hydrogen-induced amorphization and disproportionation was eliminated. From ZrMgNi4 to ZrMgNi2V2 with the increase of the degree of vanadium substitution, the reversible hydrogen storage capacity increased from 0.6 ​wt% (0.35H/M) to 1.8 ​wt% (1.0H/M), meanwhile the lattice stability gradually increased. The ZrMgNi2V2 alloy could absorb 1.8 ​wt% hydrogen in about 2 ​h ​at 300 ​K under 4 ​MPa H2 pressure and reversibly desorb the absorbed hydrogen in approximately 30 ​min ​at 473 ​K without complicated activation process. The prominent properties of ZrMgNi2V2 elucidate its high potential for hydrogen storage application.

Theoretical model on the electronic properties of multi-element AB5-type metal hydride

Nowadays, multi-element alloys are preferred over binary alloys for application point of view. The hydrogenation properties strongly depend on the thermodynamic, structural and electronic properties of the alloys. At present, no model is available which can predict the hydrogen storage properties of the multi-element alloy, before actual synthesis of the alloy. In the present investigation, efforts are made to develop a theoretical mathematical model to predict the hydrogenation properties of multi-element AB5-type metal hydride. The present investigation deals with the various electronic parameters which may affect the hydrogenation characteristics of the metal hydride. Based on all such parameters, an electronic factor has been proposed for AB5-type alloys. Electronic factor has been combined with the structural and thermodynamical factor to propose a new combined factor, which was further correlated with the hydrogen storage capacity of the alloy. Atomic radius and electronic configuration of substituted elements in the multi-element AB5-type hydrogen storage alloy have been found as key players to predict the hydrogenation properties of the alloys before synthesis. It has been shown that in the case of alloy series with multiple substitutions, the combined factor is more relevant in deciding the hydrogen storage capacity in comparison to electronic factor alone. Combined factor is directly proportional to the hydrogen storage capacity. All the three factors thermodynamic, structural and electronic together may lead to the prediction of pressure-composition isotherm of the multi-element AB5-type hydrogen storage alloy.

Electrochemical properties of AB5 type La0.8Ce0.2Ni4Co0.5Mn0.3Al0.2 alloy for unified metal hydride fuel cell

Metal hydride materials are widely applied for electrochemical energy storage. AB5 type alloys are the main anode material for Ni-MH batteries. Reversible hydrogen uptake and release provides good opportunities to use metal hydrides for alkaline fuel cell applications. Metal hydrides have good activation performance, high hydrogen sorption/desorption rates, catalytic activity in alkaline solution. Current work presents the first experimental results of AB5 type metal hydride electrodes, measured in a battery mode. The electrochemical properties of the prepared electrodes, such as activation performance, maximum discharge capacity, and high rate dischargeability are investigated in detail.