Structural, morphological, and electrochemical properties of AB5 hydrogen storage alloy by mechanical alloying

International audienceMechanical alloying (MA) is one of the most promising methods in the development of intermetallic alloys and their scientific research. In this paper, elemental powder mixtures of Ca, Ni, and Mn of nominal composition CaNi5-xMnx (with x =0.3, 0.5, and 1) were elaborated by MA technique during different milling times (2–60 h). Structural, morphological, and electrochemical changes were investigated by X-ray diffraction (XRD), scanning electron microscopy, and Ec-Lab galvanostat, respectively. The XRD test indicated that each alloy has Ni and CaNi3 or CaNi5 phases. In addition, the particle size of the ground powders is decreased with increasing milling time. Furthermore, all alloys have a very high activation capacity, whereby the activation capacity can be fully realized during the first cycle. The results showed that the most significant value of discharge capacity for all alloys was 40 h

Innovative method to estimate state of charge of the hydride hydrogen tank: application of fuel cell electric vehicles

International audienceSignificant attention has been paid to metal hydrides (MH) as an environmentally friendly and safe way to store hydrogen. This technology has considerable potential for the application of embedded hydrogen storage in fuel cell electric vehicles, but its widespread application faces a major problem in terms of estimating the remaining hydrogen amount in the tank. In this work, a new method is proposed for estimating the state of charge (SoC) of the hydrogen hydride tank (HHT) by application of piezoelectric material. The idea is to cover the entire inner wall of the metal-hydride tank with a layer of piezoelectric material. During the process of hydrogen absorption, the pressure inside the tank increases, resulting in an increase in the mechanical stress applied to the piezoelectric layer, thus generating a voltage. This effect can therefore be used as an effective means of estimating the amount of hydrogen absorbed. The COMSOL Multiphysics software was used to implement the model and solve the differential equation of energy, mass, and moment. The simulation results showed that the voltage evolution as a function of hydrogen concentration follows the same behavior as the variation of the Pressure Concentration Isotherm (PCI)

Kinetic and thermodynamic studies of hydrogen storage alloys as negative electrode materials for Ni/MH batteries: a review

International audienceThis paper reviews the present performances ofintermetallic compound families as materials for negativeelectrodes of rechargeable Ni/MH batteries. The performanceof the metal-hydride electrode is determined by both thekinetics of the processes occurring at the metal/solutioninterface and the rate of hydrogen diffusion within the bulkof the alloy. Thermodynamic and electrochemical propertiesfor each hydride compound family will be reported. The stepsof hydrogen absorption/desorption such as charge-transferand hydrogen diffusion for evaluating the electrochemicalproperties of hydrogen storage alloys are discussed. Exchangecurrent density (I 0) and hydrogen diffusion coefficient (DH)are the two most important parameters for evaluating theelectrochemical properties of metal hydride electrode. Thevalues of the two parameters for a number of hydrogen storagealloys are compared. The relationship between alloycomposition and electrochemical properties is noted andevaluated

Electrochemical study of LaGaO3 as novel electrode material of hydrogen battery (Ni/MH)

International audienceThe physico-chemical performance of the novel anode LaGaO3 forNi/MH accumulators was studied using the electrochemical impedancespectroscopy (EIS) method during cycling. The measured EIS data ofthe perovskite oxide are fitted according to the proposedequivalent circuit representing various processes involved in themechanism of hydrogenation/dehydrogenation reactions of the oxide.Different kinetic elements such as current density I0, chargetransfer resistance Rct, hydrogen transfer resistance Rht, doublelayer capacitance Cdl, and mass hydrogen diffusion Y0 wereestimated under cycling. The EIS results relieved that currentdensity I0 of the oxide increases quickly during the activationprocess and its maximum value is obtained at the second cycle(377.67 mA g_1). The degradation of the charge transfer rate of theoxide after activation can be ascribed to the corrosion of theelectrode/electrolyteinterface. The variation of the Warburgimpedance Y0 could be attributed to the change in the morphologicaland the structure of the working electrode over cycling. The EISanalysis relieved that electrochemical behavior of the oxide iscontrolled by the charge-transfer rate and the modification of theelectrode surface