Properties of Ti-Based Hydrogen Storage Alloy

An efficient and safe hydrogen storage method is one of the important links for the large-scale development of hydrogen in the future. Because of its low price and simple design, Ti-based hydrogen storage alloys are considered to be suitable for practical applications. In this paper, we review the latest research on Ti-based hydrogen storage alloys. Firstly, the machine learning and density functional theory are introduced to provide theoretical guidance for the optimization of Ti-based hydrogen storage alloys. Then, in order to improve the hydrogen storage performance, we briefly introduce the research of AB type and AB2 type Ti-based alloys, focusing on doping elements and adaptive after treatment. Finally, suggestions for the future research and development of Ti-based hydrogen storage alloys are proposed. .

Effect of Heat-Treatment Process on Properties of Rare Earth Mg-Based System Hydrogen Storage Alloys with AB_3-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.

Study on Nanocrystalline Rare Earth Mg-Based System Hydrogen Storage Alloys with AB_3-Type

A sort of rare earth Mg-based system hydrogen storage alloys with AB3-type was prepared by double-roller rapid quenching method. The alloys were nanocrystalline multi-phase structures composed of LaNi3 phase and LaNi5 phase by X-ray diffraction and scanning electron microscopy analyses, and the suitable absorption/desorption plateau was revealed by the measurement of P-C-I curve. Electrochemical studies indicate that the alloys exhibit good electrochemical properties such as high capacity and stable cycle life, and the discharge capacity is 369 mAh·g-1 at 0.2 C (72 mA·g-1). after 460 cycles, the capacity decay was only 19.4% at 2 C (720 mA·g-1).

Study on Particle Size and Electrochemical Properties of Rare Earth Based Hydrogen Storage Alloys

The rare earth based hydrogen storage alloys Ml_ 0.7Mm_ 0.3(Ni_ 3.55Co_ 0.75Mn_ 0.4Al_ 0.3) were chosen as objects of investigation in this paper. The effects of particle size on electrochemical properties of the alloy were investigated. The results indicate that the alloy with particle size of 100 and 150 mesh shows good activation behavior and high discharge capacity (the first discharge capacity and the maximum discharge capacity), but poor cycling stability, low capacity retention and high discharge capacity rate. The Ml_ 0.7Mm_ 0.3(Ni_ 3.55Co_ 0.75Mn_ 0.4Al_ 0.3) alloy with particle size of 150 mesh shows excellent electrochemical properties.

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.

Study on Phase Structure and PCT Characteristics of Rare Earth Based Hydrogen Storage Alloys

The rare earth based hydrogen storage alloys Mm_xMl_ 1-xNi_ 3.55Co_ 0.75Mn_ 0.4Al_ 0.3(x=0～0.50) were investigated in this work. The influences of phase structure on the PCT characteristics were analyzed by means of electrochemical measurements. The results indicate that there is a strict relationship between crystal volume and PCT characteristics.

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.

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

The hydriding/dehydriding thermodynamic properties of the slurry system formed by suspending La rich mischmetal nickel hydrogen storage alloy (MlNi 5) in Benzene (C 6H 6) were investigated. The pressure composition isotherms for both the alloy powder and the slurry suspended with MlNi 5 were measured at several temperatures(10, 20, 30, 40 ℃). The standard enthalpy of formation Δ H ° and standard entropy of formation Δ S ° for the alloy powder with and without benzene were determined respectively. The experimental results show that the values of Δ H ° and Δ S ° for the hydriding reaction of hydrogen storage alloy (MlNi 5) of the slurry system and the gas solid system are all very close.

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

A new type of AB_5-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composite hydrogen storage alloys were prepared by sintering the powder mixtures of a commercial AB_5 alloy and LaMg_3 alloy. The phase structure and electrochemical characteristics of the composite hydrogen storage alloys were also studied. It is shown that AB_(5)-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composites have mult; phase structure. The matrix phase has CaCu_5 structure, the second phase is LaNi_3 phase. The maximum discharge capacity, discharge capacity at low temperature and HRD of AB_5 alloy electrodes are greatly improved after the composite. The maximum discharge capacity of the composite electrodes increases from 325 mAh·g^(-1) for x=0 to 358 mAh·g^(-1) for x=5, and the HRD of the composites for x=5 at the current density of 1200 mA·g^(-1)30% of that of the alloy at 60 mA·g^(-1). The discharge capacity of AB_5-x%LaMg_3 composite alloy electrode at 233 K is up to 174 mAh·g^(-1). The improvement of the electrochemical characteristics of the composite electrodes seems to be related with formation of the LaNi_3 second phase.

Electrochemical properties of TiV-based hydrogen storage alloys

The electrochemical properties of the super-stoichiometric TiV-based hydrogen storage electrode alloys(Ti 0.8Zr 0.2)(V 0.533Mn 0.107Cr 0.16Ni 0.2) x(x=2, 3, 4, 5, 6) were studied. It is found by XRD analysis that all the alloys mainly consist of a C14 Laves phase with hexagonal structure and a V-based solid solution phase with BCC structure. The lattice parameters and the unit cell volumes of the two phases decrease with increasing x. The cycle life, the linear polarization, the anode polarization and the electrochemical impedance spectra of the alloy electrodes were investigated systematically. The overall electrochemical properties of the alloy electrode are found improved greatly as the result of super-stoichiometry and get to the best when x=5.

Effect of commercial AB_5 alloy addition on the electrochemical properties of Ml-Mg-Ni-based hydrogen storage alloys

A commercial AB5 hydrogen storage alloy was used as an additive to improve the electrochemical properties of Ml-Mg-Ni-based hydrogen storage alloys. The effect of AB5 alloy addition on the phase structure, charge/discharge characteristics, and electrochemical kinetics of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy was investigated. The maximum discharge capacity of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 ＋ 4 wt.% AB5 electrode reaches 406 mAh/g. The anodic polarization, cyclic voltammetry, and potential step discharge experiments show that the electrochemical kinetics of the electrode with additives was promoted, with the LaNi5 phase of AB5 alloy acting as electro-catalytic sites in the electrode alloy. The high-rate dischargeability of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 ＋ 4 wt.% AB5 alloy electrode at 1100 mA/g reaches 60.9%, which is 9.4% higher than that of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy electrode. The cycling stability of the electrode with 4 wt.% AB5 alloy has also been improved

Low-Co rare-earth-based hydrogen storage alloy

On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of other elements. The microstructures, p c T (pressure concentration temperature) characteristics and electrochemical propertiesunder different charge discharge conditions of the alloys have been investigated. Compared with the high Co alloy, thelow Co or Co free alloys have the lower hydrogen equilibrium pressure and discharge capacity, but have the nearly samehigh rate and high temperature discharge capability, and better charge discharge cycling stability. The reason is revealedby SEM, XPS and XRD results. \[

Characteristics of multi-component Ml-based hydrogen storage alloys and their hydride electrodes

A series of multi-component M1-based hydrogen storage alloys witha cobalt atomic ratio of 0.40-0.75 were prepared. The electrochemicalproperties under different charge-discharge conditions and PCTcharaceristics measured by electrochemical method were investigated.The addition of other alloying elements for partial substitution ofCo low- ers the hydrogen equilibrium pressure and discharge capacity,but improves the cycling stability and makes the alloys keep nearlythe same rate discharge capability and high-temperature dischargecapability as those of the compared alloy. The reasons werediscussed.

Development of Strip Casting Technology in Rare Earth Permanent Magnet Alloys and Hydrogen Storage Alloys in China

The SC technique is now being applied widely in material preparation, especially in rare earth functional materials in virtue of its advanced process and high performance product. The applications of SC technique in rare earth permanent magnet alloys and hydrogen storage alloys were analyzed integrative, on the basis of summary of SC technique development in this paper. The paper mainly includes development history of SC technology, effect of SC technology on alloy microstructure, application of SC technology in RE storage hydrogen alloy and sintered Nd-Fe-B alloy, development of SC equipment and SC product industry. At the same time, the paper points out the existing problem of SC products.

ELECTRODE PERFORMANCES OF MELT-SPINNED AB_2 TYPE Zr-BASED HYDROGEN STORAGE ALLOYS

１ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓａｓｕｍｅｄｔｈａｔｔｈｅｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓｄｅｐｅｎｄｏｎｂｏｔｈｔｈｅｃｈｅｍｉｃａｌｃｏｍｐｏｓｉｔｉｏｎａｎｄｔｈｅｍｉｃｒｏｓｔｒｕｃｔｕｒｅｏｆｈｙｄｒｏｇｅｎｓｔｏｒａ...

Development of Rare Earth Hydrogen Storage Alloys: Correlation Between Structure, Stability, and Hydrating Properties

The structure of β-LaNi2Hx is mentioned. Special emphasis is laid on the influence of substitutions with metallic elements on the thermodynamic properties of the rare-earth-nickel hydrogen storage alloys. The models of the heat of hydride formation are studied attentively. The relation between the stability and the heat of formation of intermetallic compounds including with other physical properties is discussed. The relations between hydriding properties and the geometric and electronic structure of the intermetallic compounds are presented.

Hydrogen Fixation Effect of Rare Earths in Pure Aluminium and Aluminium Alloys

The areal distribution of some elements in the rare earth bearing spheroidal phases in pure aluminium and Al-Mn alloys was studied by SIMS(secondary ion mass spectrometry).The results show that cerium,iron. silicon and hydrogen are significantly segregated in the phases.Thus the existence of hydrogen-rich rare earth bearing eompounds is confirmed.It indicates that the rare earths have a hydrogen fixation effect in aluminium and aluminium alloys.

Shell and shrinking core kinetics model of Mg-based hydrogen storage alloys

The kinetics equation of the Mg-based hydrogen storage alloys (Mg-Ni-MO) was established by the shell and shrinking core model. The total coefficients of the kinetics equation of the hydrogen absorption and desorption process with shell diffusion as the controlling step were determined by semi-empirical and semi-theoretical methods, and the apparent activation energy of the hydrogen absorption process was obtained. The calculation results can well accord with the experimental data, and can well forecast the hydrogen storage capacity and absorption rate at different times. By using the kinetics equation, the effects of temperature and pressure on the hydrogen storage process can also be well understood. The kinetics equation is helpful for the design of the hydrogen storage container.

Design of Zr-based AB_2 type hydrogen storage alloys

The influences of the ratio of the radius of atom A（rA） to radius of atom B（rB）, electronegativity and electron number were discussed on the Laves phase formation and the characteristics of Zr-based AB2 type hydrogen storage alloy. An enthalpy model of Zr-based AB2 alloy was obtained from known data and twelve Zr-based alloys were designed to test the model. The results show that the predicted values are in good agreement with the experimental values. The model can be used for predicting enthalpy values of Zr-based hydrogen storage alloys and settles a foundation for experiments.

Effect of VFe addition on hydrogen storage behavior of TiMn_(1.5)-based alloys

The hydrogen absorption and desorption behavior of TiMn_(1.25)Cr_(0.25)alloys with VFe substitution for partial Mn was investigated at 273, 293 and 313 K. It is found thatVFe substitution increases their hydrogen storage capacity, decreases the plateau pressure and thehysteresis factor of their pressure-composition-temperature (PCT) curves. After annealing treatmentat 1223 K for 6 h, TiMn_(0.95)Cr_(0.25)(VFe)_(0.3) alloy exhibits a lower hydrogen desorptionplateau pressure (0.27 MPa at 313 K) and a smaller hysteresis factor (0.13 at 313 K); the maximumand effective hydrogen storage capacities (mass fraction) are 2.03% and 1.12% respectively, whichcan satisfy the demand of hydrogen storage tanks for proton exchange membrane fuel cells (PEMFC).