Composite Hydrogen Storage Alloys Research Articles

Effect of ball milling on the structure and electrochemical hydrogen storage properties of a RE-Mg-Ni alloy

RE-Mg-Ni alloy is considered a highly promising anode material for the next generation of MH-Ni batteries. However, the low cycle life, fast performance, and high manufacturing cost of this ideal MH-Ni battery anode material have become obstacles to its optimization. In this work, an as-cast La0.7Sm0.3MgNi3.6Co0.4 superlattice alloy was prepared by vacuum medium frequency induction melting. Then, La0.7Sm0.3MgNi3.6Co0.4 + 10 wt% Ni (0–2 h) composite hydrogen storage alloys with excellent properties were prepared by adding a catalyst (Ni) and conducting ball milling. XRD, SEM, and HRTEM were conducted to analyse the phase compositions, microstructures and macrostructures of the samples. The experimental results showed that with the increase in ball milling time, the microstructural characteristics of the alloy changed, such as the phase abundance, grain refinement, particle size reduction, and amorphous structure increase, directly leading to the change in electrochemical performance. The discharge capacity (Cmax) of the sample decayed from 264.0 mAh/g to 219.1 mAh/g, the cycle stability (Sn) gradually increased with the extension of the grinding time, and the rate discharge performance first increased and then decreased. When the grinding time was 1 h, the best performance was HRD900 = 36.53%. The critical factors affecting the dynamic performance, such as the charge transfer resistance (Rct), limiting current density (IL), and hydrogen diffusion coefficient (D), all exhibited the same trend and reached their respective optimal values at 1 h.

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%.

High energy ball milling composite modification of Mg2Ni hydrogen storage alloy by graphene and MWCNTs

This study focuses on the preparation of a Mg2Ni hydrogen storage alloy through high-energy ball milling, further enhanced by composite graphene and multi-walled carbon nanotubes (MWCNTs) modification. It is evident that high-energy ball milling successfully incorporates graphene and MWCNTs onto the surface of Mg2Ni particles. This process not only creates surface defects but also establishes hydrogen pathways, facilitating the absorption and desorption of hydrogen. This improvement enhances the performance of hydrogen storage. With an increase in the composite quantity of graphene and MWCNTs, a more noticeable lubrication and grinding aid effect become evident during the ball milling process. This effect promotes more efficient grain refinement and minimizes agglomeration and welding phenomena. A comparative analysis with the Mg2Ni alloy reveals that the activation duration for the composite hydrogen storage alloy material significantly decreases. Concurrently, the kinetic performance sees substantial enhancement, and the temperature needed for hydrogen absorption and discharge is correspondingly reduced.

Hydrogen storage property improvement of ball-milled Mg2.3Y0.1Ni alloy with graphene

In this paper, Mg2.3Y0.1Ni + x wt.% graphene (x = 1, 3, 5, 7) composite hydrogen storage alloys were fabricated by mechanical ball milling of Mg2.3Y0.1Ni alloy powder and graphene. The experimental results show that the phases of the composite alloy consist mainly of Mg2Ni, Mg, MgNi2 and Ni3Y phases, and graphene tends to be distributed at the edges of the alloy, increasing the phase boundary resulting from the contact between the C-boundary and the Mg2.3Y0.1Ni alloy, providing more channels for the diffusion of H2. In which 7 wt.% of graphene is added, the gestation period of the composite alloy completely disappears. And the ball-milled alloy with 3 wt.% graphene at different temperatures has the highest hydrogen uptake in 2 min and the highest hydrogen release in 10 min. At 573 K, the composite alloy has a hydrogen absorption capacity of 3.251 wt.% H2 in 2 min and reaches 90.21% of the maximum hydrogen absorption, while it is able to release 3.389 wt.% H2 in 10 min and reaches 99.04% of the maximum hydrogen release. And the composite alloy with 3 wt.% graphene has the smallest dehydrogenation activation energy. The absolute value of the enthalpy change is reduced from 60.1 kJ/mol to 54.8 kJ/mol, and the desorption enthalpy change is reduced from 73.4 kJ/mol to 67.5 kJ/mol.

Correlation between electrochemical properties of the CNTs/AB5 composite hydrogen storage alloys and their catalytic properties for KBH4

Searching for non-precious metal anode catalysts with high catalytic activity and capable of inhibiting hydrolysis side reactions is very important for direct borohydride fuel cell (DBFC). In this work, the as-cast AB5 alloy powders are firstly mixed with CNTs in a ratio of 1:9. Then the mixture of AB5 alloy and CNTs is ball milled in different milling time. Finally, the CNTs/AB5 composite alloys are obtained. Not only the catalytic properties of the CNTs/AB5 composite alloys used as anode catalysts in DBFC, but also the electrochemical properties of the alloys have been investigated in detail. The research results indicate that, as the ball milling time is extended, the electrochemical properties and catalytic properties on ΒΗ4− of the CNTs/AB5 composite alloys become better first and then worsen. The CNTs/AB5 alloy milled 2 h exhibits the best electrochemical properties and catalytic properties. Furthermore, we predict that the electrochemical properties of the composite alloy are positively correlated with the catalytic properties as anode catalyst for DBFC.

Hydrogen storage thermodynamics and kinetics of RE–Mg–Ni-based alloys prepared by mechanical milling

The nanocrystalline/amorphous NdMg11Ni + x wt.% Ni (x = 100, 200) composite hydrogen storage alloys were synthesized by ball milling, and the effects of Ni content and milling time on the hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The results reveal that the variation of the Ni content has a slight effect on the thermodynamic properties of the alloys, but it significantly improves their absorption and desorption kinetics performance. The variation of the milling time clearly affects the hydrogen storage properties of the alloys. Hydrogen absorption capacity and hydrogen absorption saturation ratio have maximum values with milling time varying. But hydrogen desorption ratio always increases with milling time prolonging. It is found that the hydrogen desorption activation energy of the alloys clearly decreases with increasing Ni content and milling time, which is responsible for the improved hydrogen desorption kinetics of the alloys.

Gaseous hydrogen storage thermodynamics and kinetics of RE–Mg–Ni-based alloys prepared by mechanical milling

Nanocrystalline/amorphous LaMg11Ni+xNi (x=100%, 200%, mass fraction) composite hydrogen storage alloys were synthesized by ball milling technology. The effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The hydrogen desorption properties were studied by Sievert’s apparatus and a differential scanning calorimeter (DSC) connected with a H2 detector. The thermodynamic parameters (ΔH and ΔS) for the hydrogen absorption and desorption of the alloys were calculated by Van’t Hoff equation. The hydrogen desorption activation energy of the alloy hydride was estimated using Arrhenius and Kissinger methods. The results indicate that a variation in the Ni content has a slight effect on the thermodynamic properties of the alloys, but it significantly improves their absorption and desorption kinetics performances. Furthermore, varying milling time clearly affects the hydrogen storage properties of the alloys. All the as-milled alloys show so fast hydrogen absorption rate that the absorbed amount in 10 min reaches to at least more than 95% of the saturated hydrogen absorption capacity. Moreover, the improvement of the gaseous hydrogen storage kinetics of the alloys is found to be ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and prolong milling time.

Hydrogen storage thermodynamics and kinetics of LaMg11Ni + x wt.% Ni (x = 100, 200) alloys synthesized by mechanical milling

Abstract LaMg11Ni + x wt.% Ni (x = 100, 200) composite hydrogen storage alloys with a nanocrystalline/amorphous structure were synthesized using ball milling technology. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were investigated systematically. The hydrogen desorption properties were assessed using a Sieverts apparatus and differential scanning calorimetry. The thermodynamic parameters for the hydrogen absorption and desorption were calculated using the Van't Hoff equation. The hydrogen desorption activation energies of the hydrogenated alloys were also estimated by Arrhenius and Kissinger methods. Results indicate that the amount of Ni added has no effect on the thermodynamics of the alloys, but it significantly improves their absorption and desorption kinetics. Furthermore, the milling time has a great influence on the hydrogen storage properties. To be specific, the hydrogen absorption capacities reach the maximum values with the variation of milling time, and the hydrogen desorption activation energy obviously decreases with increasing milling time.

An investigation of the microstructure and hydrogenation/dehydrogenation properties of ball-milled CeMg12 alloys with Ni powders

Abstract CeMg12 + 100 wt.% Ni composite hydrogen storage alloys were prepared using ball-milling. The phase structure, morphologies, and hydrogen absorption and desorption kinetics of these alloys were systematically investigated. The results show that the milled CeMg12 + 100 wt.% Ni alloys consisted of Mg2Ni and Ni phase with nanocrystalline and amorphous structures. Additionally, the volume fractions of the phase increased with prolonged ball-milling times, which improved the hydrogenation rates and the hydrogen storage capacities of the alloy samples. However, the dehydrogenation kinetics of the alloy samples were also impaired by the increased milling times. The poor dehydriding kinetics of the alloy samples milled for 80 h and 100 h were primarily attributed to grain size effects.

Effect of ball milling time on microstructure and electrochemical properties of CeMg12+100%Ni hydrogen storage alloy

In order to improve hydrogen storage performances of CeMg12 type alloys, ball milling technology was used for preparing nanocrystalline/amorphous CeMg12+100%Ni composite hydrogen storage alloys. The microstructures and morphologies of alloy samples were characterised by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. The electrochemical hydrogen storage characteristics of as milled alloys were tested by an automatic galvanostatic system. The electrochemical impedance spectra were plotted by an electrochemical workstation (PARSTAT2273). The hydrogen diffusion coefficients D in the alloys were calculated by virtue of potential step method. The results show that the amount of nanocrystalline/amorphous Mg2Ni phase and Ni phase within alloy samples increase with prolonging milling time. Prolonging of ball milled duration markedly improves the electrochemical discharge properties and cyclic stability of alloy samples. The amorphisation degree of the milling alloys increases with rising milling duration. Furthermore, the high rate dischargeability, electrochemical impedance spectra and potential step measurement all indicate that electrochemical kinetics of alloy electrodes first increases and then decreases with increasing ball milling.

The Effect of Molding Pressure on Electrochemical Properties of the La-Mg-Ni-Based Composite Hydrogen Storage Alloy Electrodes

The Effect of Molding Pressure on Electrochemical Properties of the La-Mg-Ni-Based Composite Hydrogen Storage Alloy Electrodes

Structure and electrochemical characteristics of Ti 0.10Zr 0.15V 0.35Cr 0.10Ni 0.30–LaNi 4Al 0.4Mn 0.3Co 0.3 composite hydrogen storage alloy

Structure and electrochemical characteristics of Ti 0.10Zr 0.15V 0.35Cr 0.10Ni 0.30 (matrix alloy) — 1 mass% LaNi 4Al 0.4Mn 0.3Co 0.3 composite hydrogen storage alloy have been investigated systematically. The main phase of composite alloy is composed of V-based solid solution phase with a BCC structure and C14 Laves phase with hexagonal structure, while secondary phase which has a composition close to Zr (Ti, V, Ni, Cr, Al, Co, La) 1.8 also exists in the composite alloy. The real maximum discharge capacity of the composite alloy electrode is 354.9 mAh g −1, and distinct synergetic effect appears during composite process. Comparing with the matrix alloy, the thermodynamic performances, electrochemical characteristics, dynamic performances for the composite alloy electrode have been improved. The secondary phase is probably responsible for the improvement of electrochemical characteristics of the matrix alloy.

Recent progress in hydrogen storage alloys for nickel/metal hydride secondary batteries

This paper reviews the development of hydrogen storage alloys prepared by an effective method of mechanical alloying and milling. It emphasizes alloys based on Mg or that contain Mg due to their low cost, low weight and high hydrogen storage capacity. Hydrogen absorption/desorption and electrochemical measurements are briefly discussed. The electrochemical properties of the alloys that contain Mg are covered in detail, emphasizing the effects of changes in alloy composition. The system of Ti–Ni-based alloys is also introduced. At present, composite hydrogen storage alloys may be the most effective materials for practical application in new nickel/metal hydride secondary batteries. The steps of hydrogen absorption/desorption such as charge-transfer and hydrogen diffusion for evaluating the electrochemical properties of hydrogen storage alloys are discussed. The relationship between alloy composition and electrochemical properties is noted and evaluated.

Synthesis mechanism and properties of Mg–Mg2Ni composite hydrogen storage alloy produced by hydriding combustion synthesis

Hydriding combustion synthesis (HCS) has been regarded as an innovative process to produce magnesium based hydrogen storage alloys. In the present paper, a Mg–Mg2Ni composite hydrogen storage alloy was prepared by the HCS process under moderate conditions. Phase composition, synthesis mechanism and hydrogen storage properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure composition temperature (PCT). The results indicated that the HCS product was composed mainly of MgH2, Mg2NiH4 and Mg2NiH0·3. A gas–solid reaction mechanism played an important role in the HCS process. The hydriding activity of the as synthesised product was very high so that it absorbed 4·61 mass% hydrogen in the first hydriding process without any activation treatment and the maximum hydrogen storage capacity achieved was 5·24 mass%. Moreover, the hydriding rate was excellent. For example, it could absorb >3·20 and 4·05 mass% hydrogen within 4 min in the first and forth hydriding/dehydriding cycle respectively. The relationships between the plateau pressure and temperature were: lgP(0·1 MPa)=−4250·5/T+7·9635 (hydriding), lgP(0·1 MPa)=−4125·4/T+7·6502 (dehydriding) for the lower plateau, and lgP(0·1 MPa)=−2894·6/T+5·9656 (hydriding), lgP(0·1 MPa)=−3855·9/T+7·3435 (dehydriding) for the higher plateau.

Activation characteristics and microstructure of [formula omitted] composite hydrogen storage alloys prepared by two-step re-melting

In the present work, novel composites Mm 0.3 Ml 0.7 Ni 3.55 Co 0.75 Mn 0.4 Al 0.3 / x wt % Mg 2 Ni ( x = 0 , 5 , 10 , 30 ) for hydrogen storage were prepared by two-step re-melting and their activation characteristic and microstructure were investigated. The influence of Mg 2 Ni content on the activation characteristics was analyzed by electrochemical method. With the increasing content of Mg 2 Ni , activation characteristics and maximum discharge capacities of composites increase first and then decrease. The composite with 5% Mg 2 Ni has the least cycle number for activation and the highest discharge capacity. It is activated after only 6 cycles ( C n = 6 ) at room temperature and its maximum discharge capacity ( C max ) reaches 274.4 mAh/g. However, the composite contained 30 wt% Mg 2 Ni is difficult to be activated at room temperature. It is also found that it is easier to be activated for the composites at I c = 60 mA / g and I d = 60 mA / g than that at I c = 100 mA / g and I d = 60 mA / g , but their discharge capacity decay slightly at the condition of I c = 60 mA / g and I d = 60 mA / g . The XRD and SEM analysis show that, with the increasing Mg 2 Ni content, the microstructure of the composites varies gradually from lamellar ( x = 5 ) , acicular ( x = 10 ) to massive ( x = 30 ) , and the activity of the composite declines as a result of the grain size of phase Mg 2 Ni grows up.

Composite structure and hydrogen storage properties in Mg-base alloys

In order to improve the hydrogen absorption/desorption kinetic properties of Mg and Mg–Ni alloys, composite hydrogen storage alloys in the form of powder and film have been synthesized and investigated. For fabricating the composite powder, Mg or Mg–Ni powder was mechanically alloyed with MmNi 3.5 ( CoAlMn ) 1.5 alloy. For the preparation of the film with a composite structure, evaporation deposition and magnetron sputtering methods have been used to fabricate Mg–Ni film with multi-phase structure and Mg/Mm–Ni and Mg–Ni/Mm–Ni multi-layer film. By controlling the fabrication process, the microstructure feature, such as phase constituent, grain size, interlayer distances, interlayer boundary structure, of the composite can be modified. To reveal the influence of the composite structure on the hydrogen absorption/desorption kinetic properties of Mg and Mg–Ni alloys, hydrogen storage properties of the composite were measured with their microstructure features varied systematically. The present work shows that the hydrogen sorption properties of Mg and Mg–Ni-based alloys can be substantially improved by forming composites having proper microstructure features.

The effect of vacuum evaporation plating on phase structure and electrochemical properties of AB 5–5 mass% LaMg 3 composite alloy

In this paper, Cu, Al and Ni were plated on the AB 5–5 mass% LaMg 3 composite hydrogen storage alloy using a vacuum evaporation plating method. The phase structure and the electrochemical properties were investigated. The X-ray diffraction (XRD) analysis shows that the phase structure is not changed obviously after the plating Cu, Al and Ni on the composites. The electrochemical tests show that maximum discharge capacity, high rate dischargeability (HRD), dischargeability at low temperature and cyclic stability was improved by vacuum evaporation plating Cu, Al and Ni. Maximum of discharge capacity of the AB 5–5 mass% LaMg 3 composite alloy plating Ni can reach 351 mAh/g, which is 3.5% higher than that of the untreated. HRD at I d = 1200 mA/g of the composite alloy plating Cu is 45.0% of that at 60 mA/g, which is 20.4% higher than the untreated. Discharge capacity of the composite alloy plating Cu at low temperature 233 K is 205 mAh/g, which is 57.3% of that at 298 K, and it is much higher than 36.8% of the untreated composites. The discharge capacity retention of the composite alloy plating Al after 200 cycles is 7.8% higher than the untreated.

“Hybrid hydrogen storage vessel”, a novel high-pressure hydrogen storage vessel combined with hydrogen storage material

Potential of a novel hydrogen storage vessel, “hybrid hydrogen storage vessel”, combining an aluminum–carbon fiber reinforced plastic (Al–CFRP) composite vessel and hydrogen storage alloy, is reported through calculation of the weight and volume of the hydrogen storage system for 5 kg of hydrogen. Evaluation of this system showed that the concept of the hybrid hydrogen storage vessel allowed us to realize a hydrogen storage system advantageous in both gravimetric and volumetric hydrogen density compared with conventional hydrogen storage techniques. The hybrid vessel requires a hydrogen storage alloy with a higher volumetric hydrogen density as well as a higher gravimetric density, and with a higher equilibrium hydrogen pressure than the hydrogen storage alloys which have been used for conventional hydrogen storage vessels.

Solid state reaction and formation of nano-phase composite hydrogen storage alloy by mechanical alloying of MmNi3.5(CoMnAl)1.5 and Mg

In this work MmNi3.5(CoMnAl)1.5 and Mg were mechanically alloyed to prepare composite hydrogen storage alloys. The microstructural variation of the alloy resulted from the mechanical alloying was characterized by X-ray diffraction, SEM and TEM analysis. It was found that solid state reaction occurred between MmNi3.5(CoMnAl)1.5 and Mg components, resulting in Mm2Mg17 phase formation. The alloy obtained by ball milling contains homogeneously distributed Mg, MmNi3.5(CoMnAl)1.5 and Mm2Mg17 phases of nanometer size. It was also found that Mg2Ni was formed after the mechanically alloyed samples were annealed. The mechanism of the reaction has been proposed based on the estimation of the heat of formation using Miedema's theory and is in accordance with the experiment result of lattice constant measurement of ball milled sample and its structure variation during annealing.

Hydriding kinetics of nano-phase composite hydrogen storage alloys prepared by mechanical alloying of Mg and MmNi 5− x(CoAlMn) x

Nano-phase composite hydrogen storage alloys were prepared by mechanical alloying of Mg and MmNi 5− x (CoAlMn) x . The hydrogen absorption kinetics of the nano-phase composite and melted MmNi 5− x (CoAlMn) x alloys were measured under isobaric conditions at different temperatures. The obtained hydrogen absorption kinetic curves were fitted using various rate equations to reveal the mechanism of the hydriding reaction process. The results showed that the hydriding reaction kinetics of the nano-phase composite and melted MmNi 5− x (CoAlMn) x were different. For the nano-phase composite, the hydriding reaction was in agreement with an auto-catalysis process. For the melted MmNi 5− x (CoAlMn) x , the hydride reaction was in agreement with a nucleation and growth process. The difference in hydriding kinetics of the two alloys is discussed based on the fitting results and the microstructural characteristics of the alloys.