Hydrogen Storage Electrode Alloys Research Articles

Decoupled hydrogen and oxygen evolution for efficient water splitting by using nickel hydride batteries

Cost-effective alkaline water splitting represents a promising and sustainable approach for hydrogen production. However, the prevention of hydrogen/oxygen mixing and the efficient use of unstable renewable energy are challenging issues. Herein, we propose a novel solution involving the integration of a nickel-metal hydride (Ni-MH) battery as a redox mediator and affordable a NiFe LDHs–NiFe alloy gradient hybrid bifunctional catalysts as gas evolution electrodes, effectively decoupling the hydrogen and oxygen evolution processes during water splitting. Then, the hydrogen evolution reaction (HER) cell using hydrogen storage alloy and catalytic electrode only requires 0.28 V and the oxygen evolution reaction (OER) cell using nickel hydroxide and catalytic electrode only requires 0.25 V to reach a high current density of 100 mA cm−2. Furthermore, a NiOOH-Zn cell is introduced as an alternative, replacing the OER reaction with Zn. This NiOOH-Zn cell can be discharged without further energy input. Moreover, such a decoupled water electrolysis system can seamlessly integrate with a Ni-MH battery, providing the flexibility to efficiently convert renewable energy sources into both hydrogen and electricity. This integrated system maximizes the utilization of renewable energy, making a significant contribution to sustainable energy production.

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%.

Modulating superlattice structure and cyclic stability of Ce2Ni7-type LaY2Ni10.5-based alloys by Mn, Al, and Zr substitutions

It is a great challenge to achieve high capacity and long cyclic life for hydrogen storage electrode alloys in Ni-MH batteries, especially for superlattice alloys. This work investigates three series of single-phase LaY2Ni10.5-based alloys to tune the Ce2Ni7-type superlattice structure and electrochemical hydrogen storage properties by Mn, Al, and Zr substitutions. The Mn, Al substitutions for Ni could reduce the volume difference between [A2B4] and [AB5] subunits, thus greatly improving the cyclic performance. The maximum discharge capacity for the LaY2Ni9.7Mn0.5Al0.3 alloy is 384.1 mAh g−1, and the capacity retention S200 is as high as 76.1%. However, the partial replacement of Y with Zr dramatically reduces the discharge capacity and cyclic stability, although the subunit volume difference is even zero in the LaY1.75Zr0.25Ni9.7Mn0.5Al0.3 alloy. Detailed structural analysis shows that LaY1.75Zr0.25Ni9.7Mn0.5Al0.3 alloy exhibits greater a-axis expansion (Δa/a = 4.52%) and cell volume change (Δc/c = 15.46%) during charging than the Mn, Al-substituted alloys. The unusual expansion at the basal plane of [A2B4] and [AB5] subunits should be responsible for a considerable lattice strain (1.42%) and poor cyclic performance in the Zr-substituted alloys. This work provides new insights into the design of high capacity and long-life superlattice electrode alloys.

Electrochemical hydrogen storage performance of Mg3GeNi2 alloy

Mg3GeNi2 hydrogen storage electrode alloy was synthesized successfully via mechanical milling followed by sintering, and its electrochemical performance as the negative electrode material in a nickel-metal hydride (Ni-MH) battery was studied for the first time. Then, different amounts of nano-nickel were added to the selected alloy with the pre-milling duration of 60 h to further improve the electrochemical performance. XRD results indicate that partial substitution of Mg by Ge in Mg2Ni can form a stable new phase of Mg3GeNi2 with excellent cycle stability. Nano-Ni addition can increase dramatically the discharge capacity and electrochemical kinetics of the alloy, which is attributed to the good electrocatalytic capability of the nano-Ni. The Mg3GeNi2-5 wt.% nano-Ni sample shows the optimum overall properties with the best electrochemical kinetics and the highest discharge capacity.

A High-Energy Aqueous Manganese-Metal Hydride Hybrid Battery.

Aqueous rechargeable batteries show great application prospects in large-scale energy storage because of their reliable safety and low cost. However, a key challenge in developing this battery system lies in its low energy density. Herein, a high-energy manganese-metal hydride (Mn-MH) hybrid battery is reported in which a Mn-based cathode operated by the Mn2+ /MnO2 deposition-dissolution reactions, a hydrogen-storage alloy anode that absorbs and desorbs hydrogen in an alkaline solution, and a proton-exchange membrane separator are employed. Given the benefit derived from the high solubility and high specific capacity of the Lewis acidic MnCl2 in the cathode and the low electrode potential of the MH anode, this aqueous Mn-MH hybrid battery exhibits impressive electrochemical properties with admirable discharge voltage plateaus up to 2.2 V, a competitive energy density of about 240 Wh kg-1 (based on the total mass of the 5.5 m MnCl2 solution and the hydrogen storage alloy electrode system), good cycling stability over 130 cycles, and a desirable rate capability. This work demonstrates a new strategy for achieving high-performance and low-cost aqueous rechargeable batteries.

Improvement of electrochemical properties of Nd[sbnd]Mg[sbnd]Ni-based hydrogen storage alloy electrodes by evaporation-polymerization coating of polyaniline

In this study polyaniline (PANI) was coated on NdMgNi-based alloy surface via an evaporation-polymerization method. SEM-EDX results show that PANI coats on the alloy particle surface, and remains stable during charging/discharging cycles. With assistance of PANI in improving kinetics, high rate dischargeability at 1500 mA/g increases by 12.7% (The treating time is 45 min). Cyclic voltammogram and infrared tests on charged and discharged electrodes shows that transformation between benzene-quinone oxidation species and benzene-benzene reduction species in the charging/discharging electrochemical windows of metal hydride electrodes helps to improve high rate dischargeability by facilitating charge transfer and subsequent hydrogen diffusion. The PANI not only works as an electro-catalytic layer but also as a protective layer to improve cycling stability of NdMgNi-based alloy electrodes.

Effect of rare earth element substitution for lanthanum on structure and electrochemical characteristic of La0.8Mg0.2Ni3.3Al0.3Mo0.2 hydrogen storage alloys

The microstructure and electrochemical properties of La0.8−xMg0.2RExNi3.3Al0.3Mo0.2(x = 0.1; RE = Ce, Nd, Pr, Y, Gd, and Er) hydrogen storage electrode alloys have been investigated systematically. The results of X-ray diffraction show that the matrix phase structure of the alloys is composed of the LaNi5 phase and the La2Ni7 phase. The partial substitution of Lanthanum by rare earth elements can improve the cell volume of the LaNi5 phase. The electrochemical properties of the alloys are improved obviously. The maximum discharge capacity is improved with Ce, Nd, Pr, Er, and Y substitution. Er and Y substitution promote the cyclic durability of the alloy. Nd and Pr can improve the high-rate ability of the alloy electrodes. The electrochemical impedance spectroscopy test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with Nd and Pr substitution.

Surface modification of Mg3MnNi2 hydrogen storage electrode alloy with polyaniline

In this paper, polyaniline (PANI) has been adopted to modify the surface of Mg3MnNi2 hydrogen storage electrode alloy prepared by induction melting via chemical deposition. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) tests were performed to investigate the phase composition and microstructure. The comprehensive analysis based on the results of XRD, SEM, TEM and FT-IR indicates that PANI with a thickness of about 10 nm has been successfully polymerized on the surface of Mg3MnNi2 alloy. The discharge capacity retention (R20) of the Mg3MnNi2 alloy has been increased from 13.5% to 36.2% after modification with PANI, indicating better cycling stability. The Tafel polarization curves reveal that the surface modification of Mg3MnNi2 alloy with PANI can enhance its anti-corrosion ability. The increase of the exchange current density (Io) indicates that the surface activity of Mg3MnNi2 alloy can be improved through the surface modification with PANI. However, the high rate discharge ability (HRD) test shows that the kinetic property of Mg3MnNi2 alloy after the surface modification is declined, which is mainly due to the decline of the hydrogen diffusion in PANI, evidenced by the decreased limit current density (IL) obtained from the anodic polarization curves.

Elaboration and electrochemical characterization of Mg–Ni hydrogen storage alloy electrodes for Ni/MH batteries

Mg–Ni hydrogen storage alloy electrodes with composition of Mg–33, 50, 67 Ni at. % in amorphous phase were prepared by means of mechanical alloying (MA) process using a planetary ball mill. The electrochemical hydrogen storage characteristics and mechanisms of these electrodes were investigated by electrochemical measurements, X–ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The relationship between alloy composition and electrochemical properties was evaluated. In addition, optimum milling time and composition of Mg–Ni hydrogen storage alloy with acceptable electrochemical performance were determined. XRD results show that the alloys exhibit dominatingly amorphous structures after milling of 20 h. The electrochemical measurements revealed that the discharge capacity of Mg33Ni67 and Mg67Ni33 alloy electrodes reached a maximum when alloys were prepared after 20 h of milling time (260 and 381 mAhg−1, respectively). The maximum discharge capacity of Mg50Ni50 alloy was observable after 40 h milling (525 mAhg−1). It was also found that the cyclic stability of the alloys increased with increasing Ni content. Among these alloys, the amorphous Mg50Ni50 alloy presents the best overall electrochemical performance. In this paper, electrode process kinetics of Mg50Ni50 alloy electrode was also studied by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The impedance spectra of electrodes were measured at different depths of discharge (DODs). The observed spectra were fit well with the equivalent circuit model used in the paper. The electrochemical parameters calculated from electrochemical impedance were also compared. The electrochemical discharge and cyclic performance of 20, 40 and 60 h milled Mg50Ni50 alloy electrodes were demonstrated by the fitted charge transfer resistance and Warburg impedance obtained at various DODs. It was further observed that the controlling-step of the discharge process changed from a mixed rate-determining process at lower DODs to a mass-transfer controlled process at higher DODs. The fitted results demonstrated that charge–transfer resistance (Rct) increased with DOD. The Rct of 40 h milled Mg50Ni50 alloy (29.27 Ω) was lower than that of 20 h (41.89 Ω) and 60 h milled alloys (92.43 Ω) at fully discharge state.

Ternary Co–Ni–B amorphous alloy with a superior electrochemical performance in a wide temperature range

Ternary Co–Ni–B amorphous alloy was synthesized by a chemical reduction method. Used as a negative electrode in the alkaline rechargeable batteries, the as-prepared alloy exhibits an excellent electrochemical performance in the temperature range of −30 to 50 °C. Specifically, the discharge capacity after 100 cycles still keeps up at 395.2, 403.7, and 379.1 mAh/g at −15, 0 and 25 °C, respectively. Even at a much lower temperature of −30 °C, the maximum discharge capacity remains to be 408.3 mAh/g and slowly decays to 317.1 mAh/g after 100 cycles. Moreover, the high-rate dischargeability at 900 mA/g is 29.6% at −30 °C. When the temperature increases to 50 °C, the discharge capacity of the Co–Ni–B alloy electrode decreases from 675.6 to 283.1 mAh/g after 100 cycles. These properties are very superior to those of conventional hydrogen storage alloy electrodes at the corresponding temperatures. The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and anodic polarization (AP) tests show that the temperature has a crucial effect on the electrochemical kinetics of the Co–Ni–B alloy electrode.

High-temperature electrochemical performance of low-cost La–Ni–Fe based hydrogen storage alloys with different preparation methods

In order to optimize the microstructure and high temperature electrochemical performances of low-cost AB5-type Ml(NiMnAl)4.2Co0.3Fe0.5 hydrogen storage electrode alloys, four different preparation methods including normal solidification (NS), normal solidification and 900°C heat treatment (NS+HT), rapid solidification (RS), rapid solidification and 900°C heat treatment (RS+HT) were adopted in this work. All alloys exhibit CaCu5 type hexagonal structure and there is a small amount of A2B7 phase in NS+HT and RS+HT alloys. It is found the using of HT process can decrease the hydrogen equilibrium plateau pressure, the plateau slope and hysteresis at 40, 60 and 80°C. The NS+HT and RS+HT alloys also possess better activation, high rate discharge performance, larger discharge capacity, but poor cycling performance due to the existence of A2B7 phase which can accelerate dissolution of Ni, Mn and Fe elements in KOH alkaline electrolyte. The RS process can make alloy exhibit the best cycling performance especially at 60°C.

Structure and electrochemical property of ball-milled Ti0.26Zr0.07Mn0.1Ni0.33V0.24 alloy with 3 mass% B

The high-energy ball-milling technique is generally used to modify the surface structure and texture of materials in order to improve their physical or chemical properties. Ti0.26Zr0.07Mn0.1Ni0.33V0.24 alloy was ball-milled with 3 mass% B. Microstructure of Ti0.26Zr0.07Mn0.1Ni0.33V0.24-3 mass% B hydrogen storage electrode alloys have been investigated using XRD, FESEM–EDS and EIS measurements. The ball-milled alloys are composed of V-based solid solution phase and C14 Laves phase. It is indicated that the ball-milling with B did not influence the bulk crystal structure of the Ti0.26Zr0.07Mn0.1Ni0.33V0.24 alloy. The ball-milling with B greatly decreased the maximum discharge capacity of the powder electrodes, but the cyclic stability of the ball-milled alloys is noticeably improved. The capacity retention rate after 45 cycles increases from 42% (t = 20 min) to 63.9% (t = 90 min). The high-rate dischargeability at the discharge current density of 600 mA g−1 increases from 45.6% (t = 20 min) to 59.7% (t = 90 min).The improvement in electrochemical kinetic properties of the ball-milled alloys should be ascribed to the increasing the exchange current density and hydrogen diffusion coefficient.

Effect of TiMn1.5 alloying on the structure, hydrogen storage properties and electrochemical properties of LaNi3.8Co1.1Mn0.1 hydrogen storage alloys

A series of experiments were performed to investigate the effect of TiMn1.5 alloying on the structure, hydrogen storage properties and electrochemical properties of LaNi3.8Co1.1Mn0.1 hydrogen storage alloys at 303 K. For simple, A, B, and C are used to represent alloys (x = 0 wt %, x = 4 wt % and x = 8 wt %) respectively. The results of XRD and SEM show that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloys have LaNi5 phase and (NiCo)3Ti phase. Based on the results of PCT curves, the hydrogen storage capacities of LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloys are about 1.28 wt % (A), 1.16 wt % (B) and 1.01 wt % (C) at 303 K. And the released pressure platform and the pressure hysteresis decrease with the increase of TiMn1.5 content. Meanwhile the activation curves show that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloy electrodes can be activated in three times and the maximum discharge capacity is 343.74 mA h/g at 303 K. In addition, with the increase of TiMn1.5 content, the cyclic stability of the hydrogen storage alloy electrodes decreases obviously and the capacity retention decreases from 76.70% to 70.00% when TiMn1.5 content increases from A to C. It also can be seen that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloy electrode C and B have the best self-discharge ability and the best high-rate discharge ability from self-discharge curves and high-rate discharge curves.

Effect of particle size on the performance of rare earth–Mg–Ni-based hydrogen storage alloy electrode

Rare earth–Mg–Ni-based hydrogen storage alloy has been synthesized by vacuum induction levitation melting and sieved into five particle size fractions from 120 mesh to below 800 mesh. The effect of particle size on the electrochemical behaviors has been investigated. It was found that the alloy electrode with the particle size of 220–325 mesh exhibited better cyclic stability and high rate dischargeability than the larger or smaller alloy powders. The pulverization and the surface oxidation/corrosion have been studied by SEM, AES, and XPS methods. The results showed that the pulverization rate became faster with the increase of the particle size. The formation of an oxide layer with proper thickness during cycling can effectively improve the cyclic stability for the 220–325 mesh alloy electrode. The capacity degradation and the electrochemical kinetics of the alloy electrodes of different particle sizes are determined by the pulverization rate and the oxidation of active components on the alloy surface during cycling in the alkaline electrolyte.

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

Electrochemical Properties Prediction of (La, Ce, Pr, Nd)2MgNi9 Hydrogen Storage Electrode Alloys by Using Support Vector Regression

Electrochemical Properties Prediction of (La, Ce, Pr, Nd)₂MgNi₉ Hydrogen Storage Electrode Alloys by Using Support Vector Regression

Carbon nanotube buckypaper/MmNi5 composite film as anode for Ni/MH batteries

An efficient and cost-effective method has been developed to produce high quality buckypapers from multi-walled carbon nanotubes. The buckypapers were then used as a substrate for AB5 hydrogen storage alloy electrodes, and electrochemical performances of these composite films in Ni/MH batteries have been investigated. AB5 alloy was coated on the buckypaper using magnetron sputtering. The buckypapers prepared by our approach were thin, highly flexible and provided sufficient strength as substrates for the hydrogen storage alloy film. A good contact between the buckypaper and the MmNi5 alloy was established. The electrochemical results show that the buckypapers can be a versatile replacement for conventional metal substrates for the anode in Ni/MH batteries. They provide exceptional electrical conductivity and significant reduction in weight and cost. The obtained maximum discharge capacity of 276 mAh/g for BM-1 electrode is higher than what was previously obtained on electrode with metal substrate of 220 mAh/g. Amongst the two different thickness of AB5 film studied, it was found that the reduction of MmNi5 layer thickness enhanced the discharge capacity of the electrode, but the high rate discharge capability was irrelevant to the film thickness. However, the thicker film exhibits better chargeability and cycle stability. Thus all these are beneficial for the miniaturisation of the Ni/MH batteries.

Structural and electrochemical hydrogen storage properties of Mg 2Ni-based alloys

Four different methods, i.e. hydriding combustion synthesis + mechanical milling (HCS + MM), induction melting (followed by hydriding) + mechanical milling (IM(Hyd) + MM), combustion synthesis + mechanical milling (CS + MM) and induction melting + mechanical milling (IM + MM), were used to prepare Mg 2Ni-based hydrogen storage alloys used as the negative electrode material in a nickel–metal hydride (Ni/MH) battery. The structural and electrochemical hydrogen storage properties of the Mg 2Ni-based alloys have been investigated systematically. The XRD results indicate that the as-milled products show nanocrystalline or amorphous-like structures. Electrochemical measurements show that the as-milled hydrides exhibit higher discharge capacity and better electrochemical kinetic property than the as-milled alloys. Among the four different methods, the HCS + MM product possesses the highest discharge capacity (578 mAh g −1), the best high rate dischargeability (HRD) and the highest exchange current density (58.8 mA g −1). It is suggested that the novel method of HCS + MM is promising to prepare Mg-based hydrogen storage electrode alloy with high discharge capacity and activity.

Advanced hydrogen storage alloys for Ni/MH rechargeable batteries

Hydrogen storage alloys are of particular interest as a novel group in functional materials owing to their potential and practical applications in Ni/MH rechargeable batteries. This review is devoted to the specific alloy families developed for high-energy and high-power Ni/MH batteries in the last decades, especially for EV, HEV and PHEV applications. The scope of the work encompasses principles of Ni/MH batteries, electrochemical hydrogen storage thermodynamics and kinetics, prerequisites for hydrogen storage electrode alloys and recent advances in hydrogen storage electrode alloys. Rare earth AB5-type alloys, Ti- and Zr-based AB2-type alloys, Mg-based amorphous/nanocrystalline alloys, rare earth-Mg–Ni-based alloys and Ti–V-based alloys are highlighted. Additionally, the challenges met in developing advanced hydrogen storage alloys for Ni/MH rechargeable batteries are pointed out and some research directions are suggested.

Crystal structure and some dynamic performances of Ti0.25V0.34Dy0.01Cr0.1Ni 0.3 hydrogen storage electrode

Abstract Crystal structure and some dynamic performances of Ti0.25V0.34Dy0.01Cr0.1Ni0.3 hydrogen storage electrode alloy have been investigated by XRD, FESEM-EDS, TEM and EIS measurements. The result shows that the alloy is mainly composed of V-based solid solution phase with body-centered-cubic structure and mono-crystal Ni3Ti phase with hexagonal structure (Space grope: P63/mmc), and it was first observed as TiNi-based secondary phase. The higher charge transfer resistance, higher apparent activation energy and lower hydrogen diffusion coefficient are reasons for the poor electrochemical activity of the dehydriding kinetics of Ti-V-Cr-Ni hydride alloy.