Metal Hydride Batteries Research Articles

Phase Transformation and Electrochemical Feature of an AB4-Type La0.60Sm0.20Mg0.20Ni3.50Al0.20 Hydrogen Storage Alloy for Ni/MH Batteries

La–Mg–Ni-based alloys with a novel AB4-type superlattice structure is supposed as potential anode materials for nickel metal hydride (Ni/MH) batteries due to the excellent discharge ability at high rates and long cycling life. However, it is still challenging to achieve high phase content of the AB4-type structure during annealing due to the complex peritectic reaction of virous superlattice structures. Herein, we study the phase transformation of the AB4-type structure upon annealing and elucidate its effect on electrochemical characteristics based on a La0.60Sm0.20Mg0.20Ni3.50Al0.20 alloy. It is found that the AB4-type phase forms between 970 °C–1000 °C by a peritectic reaction of A5B19- and CaCu5-type phases. The existence of AB4-type phase drives the alloy a higher discharge capacity of 366 mAh g–1 at 60 mA g–1, and 135 mAh g–1 at 1800 mA g–1 owing to the advantages of charge transfer and hydrogen diffusion. Moreover, high capacity retentions of 88.7% and 79.3% at the 100th and 200th cycles are respectively achieved. Besides, the alloy with the AB4-type phase shows improved tolerance at a low temperature of –40 °C. We expect that our finding can provide guidance for developing AB4-type hydrogen storage alloy for Ni/MH.

Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3·8H2O

Rare earth elements (REEs) are essential for permanent magnets that are vital for wind turbines and electric vehicles motors (EV), and are also used in a range of high-tech devices such as smartphones, digital cameras, and electronic displays. Nickel metal hydride (NiMH) batteries have been identified as a potential source due to their short lifespans and an anticipated boom in the production of EV. The aim of this study was to investigate the effect of mesomixing on crystal quality in a non-confined impinging jet mixer (NCIJM) during antisolvent crystallization of 3.2 g/L Nd2(SO4)3 from a synthetic leach solution of NiMH battery using ethanol at an O/A ratio of 1.1. The jet streams were supplied at a Reynolds number (Re) between 7500 and 15,000. The product slurry was allowed to further crystallize in a stirred batch crystallizer at a Re of 13,000 for 45 s. An average yield of 90% was achieved. Laser diffraction and scanning electron microscopy (SEM) were used for size analysis. The initial results were inconclusive due to the secondary mixing effect in the stirred batch crystallizer. Therefore, the experiments were repeated, and samples were collected immediately after mixing in the NCIJM onto a porous grid placed on a high absorbance filter paper to abruptly halt crystallization. The samples were analysed using a transmission electron microscope (TEM), and the acquired images were processed using ImageJ to obtain crystal size distributions (CSDs). It was found that the enhanced mesomixing conditions resulted in smaller crystal sizes and narrower CSDs. This was because the nucleation rate was found to be mass-transfer-limited, such that higher mesomixing intensities promoted the nucleation rate from 6 × 1012 to 5 × 1013 m−3 s−1 and, therefore, favoured the formation of smaller crystals. In parallel, intensified mesomixing resulted in uniform distribution of the supersaturation and, hence, narrowed the CSDs.

Surface Modifications of Magnesium-Based Materials for Hydrogen Storage and Nickel–Metal Hydride Batteries: A Review

Whether it is fossil energy or renewable energy, the storage, efficient use, and multi-application of energy largely depend on the research and preparation of high-performance materials. The research and development of energy storage materials with a high capacity, long cycle life, high safety, and high cleanability will improve the properties of energy storage systems and promote their wide application. In recent years, Mg-based materials, from a comprehensive consideration of energy storage performance, raw material reserves, and prices, have demonstrated potential industrial applications as large-scale hydrogen storage materials. Nevertheless, Mg-based materials also have obvious disadvantages: as a hydrogen storage material, the hydrogen absorption/desorption rate is insufficient, as well as the high hydrogen absorption/desorption temperatures; as the electrode material of Ni-MH batteries, the reactions of Mg with alkaline electrolyte and corrosion are the main problems for applications. This article reviews different surface treatment methods and mechanisms for surface modifications of Mg-based materials for hydrogen storage and Ni-MH battery applications, as well as the performance of the materials after surface modifications. Multiple experimental studies have shown that the surface layer or state of Mg-based materials has a strong impact on their performance. Surface modification treatment can greatly improve the energy storage performance of magnesium-based materials for hydrogen storage and Ni-MH battery applications. Specifically, Mg-based materials can have a lower hydrogen absorption/desorption temperature and a faster hydrogen absorption/desorption rate when used as hydrogen storage materials and can improve the corrosion resistance, initial discharge capacity, and cycling stability in alkaline solutions when used as negative electrode materials for Ni-MH batteries. By offering an overview of the surface modification methods for Mg-based materials in two energy storage fields, this article can improve researchers’ understanding of the surface modification mechanism of Mg-based materials and contribute to improving material properties in a more targeted manner. While improving the material properties, the material’s preparation and surface modification treatment process are considered comprehensively to promote the development, production, and application of high-performance Mg-based materials.

In situ diffraction studies of phase-structural transformations in hydrogen and energy storage materials: An overview

The paper presents an overview of advanced in situ diffraction studies as a highly valuable tool to probe the structure and reacting mechanisms of hydrogen and energy storage materials. These studies offer benefits from the use of a high flux diffraction beam in combination with high resolution measurements, and allow, even when using very small samples, establishing the mechanism of the phase-structural transformations and their kinetics based on a rapid data collection for the various charge-discharge states at variable test conditions. The applied conditions include a broad range of hydrogen/deuterium pressures, from vacuum to high pressures reaching 1000 bar H2/D2, and temperatures, from cryocooling (2 K) to as high as 1273 K (1000 °C). Simultaneously, various state-of-charge and discharge are probed when studying metal-H/D systems for hydrogen/deuterium gas storage and as anode electrodes of metal hydride batteries. The range of the studied systems includes but is not limited to the AB5, AB2 Laves type, AB, equiatomic ternary ABC intermetallics and Mg-containing layered AB3 structures and composites. Prospects on Li-ion full cells are considered as well. Interrelations between the structure and hydrogen storage performance, including maximum and reversible H storage capacity, hysteresis of hydrogen absorption and desorption, H2 absorption and desorption in dynamic equilibrium conditions, are considered and related to the ultimate goal of optimisation of the H storage behaviours of the advanced H storage materials. Numerous contributions of Dr. Michel Latroche to the field are highlighted, particularly in in situ studies during electrochemical transformations. The paper summarises a long-standing collaboration of the co-authors in the field, which also included 29 joint topical publications with Dr. Michel Latroche, and references 163 original publications.

Upcycling of nickel oxide from spent Ni-MH batteries as ultra-high capacity and stable Li-based energy storage devices

Due to the rapid expansion of portable electronics and electric vehicles market, the projected demand of rechargeable batteries is huge and may lead to shortage of critical minerals, especially nickel (Ni) metal. In the present study, we upcycled NiO material from spent Nickel–Metal hydride batteries (Ni-MH) as electrodes in Li-ion battery (LIB) and supercapacitor. Intriguingly, recycled NiO was applied successfully to develop sustainable LiNi0.5Mn1.5O4 (LNMO) cathode, delivering the promising capacity. As the recovered NiO-anode in LIBs, the device exhibited ultrahigh capacity of 1248 mAh g−1 at 0.1C, exhibiting excellent rate capability and cycle life in traditional carbonate-based electrolyte. The full cell with NMC cathode gave a high discharged capacity of 137.4 mAh/g. Addition to conventional electrolyte, a safe and non-flammable diglyme electrolyte using recovered NiO was investigated under identical condition. The maximum reversible capacity of 642 mAh g−1 at 0.1C was achieved along with good rate performance. Likewise, the NiO-based supercapacitor electrode delivered a maximum capacitance of 106C g−1 at 0.5 A g−1. Hence, upcycling of abundant NiO waste as low-cost electrode materials from end-of-life batteries paves the way for future generation of Li-based energy storage devices and sustainable supply of critical minerals and clean environment.

Studies of the effect of Hf doping on the electrochemical performance of C15 Laves type metal hydride battery anode alloys

This paper focuses on the studies of the electrochemical performance of arc-melted Hf-modified Ti-Zr based AB2 Laves type metal hydride battery anode alloys with composition HfxZr24-xTi6.5V3.9Mn22.2Fe3.8Ni38La0.3Sn0.3 (x = 1–4). The phase composition and the morphology of the alloys were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Metal-gas interactions and electrochemical performances were studied by building PCT diagrams and by electrochemical tests performed in a 9 N KOH electrolyte solution at ambient temperature when using the half-cells in a three-electrode assembly.All studied alloys were two-phase and contained the Laves phase intermetallics of C15 (major constituent) and C14 (minor constituent) types. An increase in Hf content caused a growth of the abundance of the C14 phase and was accompanied by a decrease in the electrochemical discharge capacities, exchange current densities, and H diffusion rates as compared to the Hf-free alloy. Among the Hf-containing alloys, an introduction of 2 wt% Hf into the alloy's composition resulted in a higher H diffusion rate, while the highest H storage capacity has been reached for the alloy with the lowest, 1 wt%, content of Hf. The surface of the alloys contained catalysing hydrogen exchange metallic nickel clusters with the highest enrichment observed for the 2 wt% Hf alloy. An influence of Hf on the hydrogen storage and electrochemical performance can be understood in terms of the modification of the intrinsic properties of the alloys following a substitution (Zr/Ti) → Hf as C15 type alloys show the fastest hydrogen diffusion rates while a gradually increasing content of the hexagonal C14 type in the Hf-containing alloys slows down the H diffusion process.

Green Extractants in Assisting Recovery of REEs: A Case Study.

The recycling of REEs from the end of life (EoL) products, such as nickel metal hydride batteries (NiMH), offers great opportunities for their supply in Europe. In the presented paper, the application of 'green' extractants such as citric (CA), metatartaric (TA), and ethylenediaminedisuccinic acid (EDDS) (also with H2O2 addition) for the recovery of REEs was studied. The studies were conducted considering the effects of the phase contact time, the initial concentration of CA, TA, and EDDS, as well as H2O2, pH, and temperature. It was found that the addition of TA to the CA solution meant that higher rates of metal ion binding and, thus, leaching was observed. The optimal conditions were obtained in the system: CA-TA and H2O2 for the concentration 0.6M-0.3 M-2%.

Generalized Peukert Equation with Due Account of Temperature for Estimating the Remaining Capacity of Nickel–Metal Hydride Batteries

In this paper, it is experimentally proven that the generalized Peukert equation C(i,T) = Cm(T)/(1 + (i/i0(T))n(T)) is applicable to nickel–metal hydride batteries at any discharge currents, while the classical Peukert equation can be used only in a limited range of the discharge currents (approximately from 0.3 Cn to 3 Cn). In addition, the classical Peikert equation does not take into account the influence of the temperature of a battery on its released capacity. It is also proven that for the nickel–metal hydride batteries, the generalized Peukert equation heavily depends on battery temperature (via the parameters Cm(T), i0(T) and n(T)). The temperature dependencies of the parameters of the generalized Peukert equation and their physical meaning are also established. The obtained generalized Peukert equation, which considers the batteries’ temperature, can be used at any discharge current and temperature of the batteries.

Selective separation of lanthanide group in spent NiMH battery acidic leaching solutions

A novel selective separation of lanthanide group (Ln) known as rare earth elements (REEs) from acidic leaching solutions of spent nickel metal hydride (NiMH) batteries was examined using precipitation at low pH with disodium phosphate, Na2HPO4, as precipitation agent. The acidic leaching solutions containing lanthanides (La, Ce, and Nd) and base metals (Ni, Cd, Mn, Fe, Al, and Zn) were from spent NiMH batteries subject to subcritical water extraction (SWE) process using 0.5 mol/L of HCl, HNO3, and H2SO4 solution, respectively. The effects of important parameters such as the molar ratio of lanthanides to phosphate ions, Ln/P, to form precipitates of lanthanide phosphates (Ln(PO4)), pH and temperature were investigated. The recovery efficiency of lanthanides increased when decreasing Ln/P, while increased with increasing pH and temperature. The decrease in the concentration of Ln remaining in HCl and HNO3 leaching solutions was proportional to the decrease in the P concentration in leaching solutions, while different results were found in the leaching solution of H2SO4 due to the formation of another insoluble lanthanide mineral, double sulfate (NaLn(SO4)2·H2O). This separation process demonstrated that the high-purity lanthanide group including La, Ce, and Nd from spent NiMH batteries could be obtained simply by adding phosphate ions at low pH. It is efficient, effective, and selective for critical rare metals recovery from spent NiMH batteries.

Surface Treatments of Metal Hydride Anode Material for Next-Generation Nickel-Metal Hydride Battery

The development of the emergency call system (eCall system) was promoted by increasingly harsh and strict policies in many countries to enhance safety of drivers and passengers. A reliable battery technology with advantages of wide operating temperature range, long shelf life, ease of maintenance, and safety is essential to power and implement the eCall system. Nickel metal hydride (NiMH) battery and lithium-ion battery (LIB) are two of the most mature rechargeable battery technologies and candidates for eCall system. Compared to LIB, NiMH battery is a safer choice due to the intrinsic non-flammability of aqueous electrolyte. Moreover, NiMH battery has better low temperature performance than LIB because ions are more mobile in aqueous electrolytes than in organic electrolytes. Hence, NiMH battery is a promising alternative for safety-sensitive application. A limitation of today’s NiMH technology is that anode materials capable of discharging at low temperature (-40°C) have short cycle and calendar life. This is due to the fracture and dissolution of active materials during cycling. In this work being presented, we have coated the metal hydride anode material with lanthanum trifluoride (LaF3), which is insoluble in alkaline electrolyte and inert at anode operating potential window, to encapsulate the particle and improve capacity retention. The coated particle achieved stable cycling over 200 cycles at room temperature. Moreover, the LaF3 coating is electrically conductive and does not affect the kinetics. The coated particle still achieved more than 150 mAh/g at extremely low operating temperature (-40°C). Thorough material characterization has been carried out to investigate the structure of the coating and correlate to the performance enhancement.

Laves type intermetallic compounds as hydrogen storage materials: A review

Laves type AB 2 intermetallics belong to the most abundant group of intermetallic compounds containing over 1000 compounds. A large variety of the chemical nature of A (Mg, Ca, Ti, Zr, Rare Earth Metals) and B (V, Cr, Mn, Fe, Co, Ni, Al) metals together with the existence of the extended solid solutions formed by mixing various selected components on both A and B sites dramatically extends the list the known binary and ternary individual compounds. A vast majority of the Laves type intermetallics crystallises with C15 / FCC MgCu 2 and C14 / hexagonal MgZn 2 types of structures, both formed for a large range of ratios between the atomic radii of the A and B components outside the ideal ratio r A / r B = 1.225. Their hydrogenation performance is defined by the chemical composition and structure of the alloys and proceeds according to the following alternative / parallel mechanisms: (a) Formation of the insertion type interstitial hydrides containing up to 6–7 at. H/f.u.AB 2 ; (b) Amorphisation of the alloys on hydrogenation; (c) Disproportionation with the formation of a binary hydride of the A metal and depleted by A metal B-components based alloys/hydrides. Equilibrium pressures of hydrogen desorption from the AB 2 -type hydrides span a huge range of ten orders of magnitude and thus Laves type-based intermetallics satisfy the requirements for various applications including getters of hydrogen gas, volume- and mass-efficient hydrogen storage materials operating at ambient conditions, materials for the efficient thermally driven compression of hydrogen gas with an output pressure of several hundred bar and high capacity and high rate anode materials for the metal hydride batteries operating in a challenging temperature range - at subzero temperatures and also above 60 °C. The paper contains references to 245 publications and will guide the future work in the areas of fundamental research and also in advancing the applications of the hydrides of the Laves type intermetallics. • Laves type AB 2 intermetallics are the most abundant group of alloys. • Hydrogenation performance is defined by the chemical composition and structure. • Mechanisms of hydrogenation: interstitial hydrides / amorphization / disproportionation. • Structure-properties relationships are described. • Important applications are reviewed: H stores/MH compression/MH batteries/H getters.

Ultra-precision machining of cerium-lanthanum alloy with atmosphere control in an auxiliary device

Cerium–lanthanum alloys are the main component of nickel–metal hydride batteries, and they are thus an important material in the green-energy industry. However, these alloys have very strong chemical activity, and their surfaces are easily oxidized, leading to great difficulties in their application. To improve the corrosion resistance of cerium–lanthanum alloys, it is necessary to obtain a nanoscale surface with low roughness. However, these alloys can easily succumb to spontaneous combustion during machining. Currently, to inhibit the occurrence of fire, machining of this alloy in ambient air needs to be conducted at very low cutting speeds while spraying the workpiece with a large amount of cutting fluid. However, this is inefficient, and only a very limited range of parameters can be optimized at low cutting speeds; this restricts the optimization of other cutting parameters. To achieve ultraprecision machining of cerium–lanthanum alloys, in this work, an auxiliary machining device was developed, and its effectiveness was verified. The results show that the developed device can improve the cutting speed and obtain a machined surface with low roughness. The device can also improve the machining efficiency and completely prevent the occurrence of spontaneous combustion. It was found that the formation of a build-up of swarf on the cutting tool is eliminated with high-speed cutting, and the surface roughness (Sa) can reach 5.64 nm within the selected parameters. Finally, the oxidation processes of the cerium–lanthanum alloy and its swarf were studied, and the process of the generation of oxidative products in the swarf was elucidated. The results revealed that most of the intermediate oxidative products in the swarf were Ce3+, there were major oxygen vacancies in the swarf, and the final oxidative product was Ce4+.

A systematic analysis of the costs and environmental impacts of critical materials recovery from hybrid electric vehicle batteries in the U.S.

SummaryCritical materials such as rare earth underpin technologies needed for a decarbonized global economy. Recycling can mitigate the supply risks created by the increasing demand and net import dependence, and enable a circular economy for critical materials. In this study, we analyze the feasibility and life-cycle impacts of recovering critical materials from spent nickel metal hydride batteries from hybrid electric vehicles in the U.S., accounting for stocks, battery scrappage, and end-of-life reverse logistics, given uncertain future availability scenarios. Our results show that the total collection and recycling costs depend strongly on future battery availability, with marginal costs exceeding marginal revenues when the availability of spent batteries declines. We quantify the potential of recycling to reduce primary imports, as well as the accompanying climate change and resource impacts. We explore the underlying reverse logistics infrastructure required for battery recycling and evaluate strategies for reducing associated capital investment risk.

A Molten-Salt Battery for Seasonal Energy Storage

Cost-competitive renewable energy sources, such as wind and solar energy, are more rapidly replacing fossil fuels for power generation. As their integration into the power grid increases, the inherent intermittency exposes a great challenge in maintaining the grid stability. Therefore, the development of low-cost energy storage technology suitable for large-scale manufacturing is essential for the further deployment of renewable energy. We noticed that renewable electricity production usually follows predictable seasonal trends. For example, the longer daylight in summers corresponds to more solar power generated. If any seasonal excess can be efficiently stored and redistributed in times of needs, a power grid based on 100% renewable energy is more feasible. Unfortunately, current rechargeable battery technologies have not been optimized for seasonal storage, as the self-discharge rate ranges from approximately 3–5% for lithium-ion batteries to almost 30% for nickel metal hydride batteries in the first month.In this presentation, we will demonstrate the concept of a rechargeable molten-salt battery with earth-abundant elements and simple construction that preserve the stored energy for long periods of time. Due to its unique operating mechanism, this battery can discharge most of its stored capacity (> 90%) after a period of 1 to 8 weeks. This approach brings new possibilities to seasonal energy storage and helps the grid to overcome short supply during seasonal fluctuations.

Efficient Recovery of Rare Earth Elements and Zinc from Spent Ni-Metal Hydride Batteries: Statistical Studies.

Considering how important rare earth elements (REEs) are for many different industries, it is important to separate them from other elements. An extractant that binds to REEs inexpensively and selectively even in the presence of interfering ions can be used to develop a useful separation method. This work was designed to recover REEs from spent nickel–metal hydride batteries using ammonium sulfate. The chemical composition of the Ni–MH batteries was examined. The operating leaching conditions of REE extraction from black powder were experimentally optimized. The optimal conditions for the dissolution of approximately 99.98% of REEs and almost all zinc were attained through use of a 300 g/L (NH4)2SO4 concentration after 180 min of leaching time and a 1:3 solid/liquid phase ratio at 120 °C. The kinetic data fit the chemical control model. The separation of total REEs and zinc was conducted under traditional conditions to produce both metal values in marketable forms. The work then shifted to separate cerium as an individual REE through acid baking with HCl, thus leaving pure cerium behind.

Dry chlorination of spent nickel metal hydride battery waste for water leaching of battery metals and rare earth elements

An efficient leaching process was developed for nickel, cobalt, and the rare earth elements (REEs) from spent nickel metal hydride (NiMH) battery waste. The process involves dry chlorination with ammonium chloride in low temperature to produce water-soluble chlorinated compounds, followed by simple water leaching. The factors affecting the conversion and solubilization were studied, including the amount of ammonium chloride, residence time and temperature in dry chlorination, and solid to liquid ratio, time and temperature in water leaching. As a result, the dry chlorination process was found to produce ammonium and chloride containing products, depending on the temperature of the process: ammonium metal chlorides were produced in temperatures of 250–300 ℃, while increasing the temperature to 350 ℃ resulted in formation of metal chlorides. Overall, highest metal recoveries were achieved during 60 min residence time at a temperature of 350 °C, where ammonium is no longer present and ammonium metal chlorides and metal chlorides have formed. Water leaching was found to proceed rapidly, especially for REEs, and yields of 87% for Ni, 98% for Co, 94% for Ce, and 96% for La were attained during 60 min of leaching in room temperature. This study introduces a process, which is considered as an environmentally more benign alternative to traditional mineral acid leaching, resulting in high metal leaching efficiencies with neutral leachates, requiring no chemical-intensive neutralization steps in the following processing.

Electrochemical study of the LaFe0.8Ni0.2O3 perovskite-type oxide used as anode in nickel-metal hydride batteries

The electrochemical hydrogen storage properties of the LaFe0.8Ni0.2O3 perovskite-type oxide used as the negative electrode in the nickel metal-hydride battery have been studied in this work. This oxide has been synthesized by the sol-gel method and its structure and electrochemical properties are systematically studied. X-ray diffraction (XRD) analysis showed that the LaFe0.8Ni0.2O3 perovskite-type oxide consists of a single phase and crystallizes in the orthorhombic space group with the Pnma space group. The electrochemical cycling properties of the LaFe0.8Ni0.2O3 negative electrode were carried out at 25 °C using the galvanostatic charging and discharging polarization method for 50 cycles. An optimization of the experimental parameters were carried out in order to optimize the charging potential, the charging and discharging current and the charging time. The best properties were observed for the optimal parameters, such as a discharge potential of 0.4V, a charge and discharge current of 4.44 mA g−1 and a charge time of 5 h.

The Hazards of Electric Car Batteries and Their Recycling

In recent years, under the double pressure of energy exhaustion and environmental deterioration, the development of electric vehicles has become the major development trend of the automotive industry in the future. This paper discusses the problem of abandoned batteries caused by the limited life of a large number of batteries with the prosperity of new energy vehicle industry. This paper lists and analyzes the different characteristics of batteries commonly used by three new energy vehicles in the market :(1) lead-acid batteries will not leak in the use process due to tight sealing, but their use cycle is very short. (2) The production of nickel metal hydride battery is relatively mature, its production cost is low, and compared with lithium electronic battery is safer. (3) Lithium-ion batteries are made of non-toxic materials, which makes them known as “green batteries”. However, they are expensive to make and have poor compatibility with other batteries. Because discarded batteries pose a threat to human health and environmental sustainability, lithium-ion batteries may overheat and fire when exposed to high temperatures or when penetrated, releasing carbon monoxide and hydrogen cyanide that can be very harmful to human health. In addition, waste batteries will also cause water pollution and inhibit the growth and reproduction of aquatic organisms and other potential dangers. Therefore, it is necessary to recycle it efficiently. This paper then introduces the advantages of three recycling methods: step utilization and recovery, ultrasonic recovery and sodium ion battery. These recycling methods can maximize the reuse efficiency of waste batteries. This paper expects to find a better way to recycle waste batteries to solve the potential problems of improper disposal of waste batteries and reduce the environmental hazards of waste batteries.

Separation of lanthanum and neodymium in a hollow fiber supported liquid membrane: CFD modelling and experimental validation

Nickel metal hydride batteries find extensive use in many electronic devices. They contain a small amount of rare earth elements, such as, lanthanum and neodymium, which can be recovered from waste batteries, and reused. Hollow fiber supported liquid membranes (HFSLM) have been used for separation of different metal ions. In this work, a CFD model has been developed for a HFSLM to study the separation of lanthanum ion (La+3) and neodymium ion (Nd+3) from an aqueous solution. The model considers the effect of pH on distribution coefficient DM, which is a function of hydrogen ion (H+) concentration, and has a significant effect on extraction efficiency. The model was validated with the experimental data. An empirical model was fitted with the simulation data, and the parameters were optimized for the effective separation of La+3 and Nd+3. The maximum extraction of Nd+3 was predicted to be 44.97%, whereas extraction of La+3 was estimated to be 3.39%, at the optimized conditions of flow rate: 118.96 ml/min, feed pH: 3.41, and [PC88A]: 41.63 mol/m3, in once-through mode. The proposed CFD model could be helpful in design as well as, scale-up of HFSLM for separation of metal ions, by changing the design and process parameters.

SYNTHESIS AND ELECTROCHEMICAL HYDROGENATION OF Tb2Co17-х-ySbxLiy AND Tb2Co17-х-yAlxMgy PHASES

Metal hydride batteries have a high sorption ability to the reverse hydrogen absorption, moderate pressure and temperature of the processes of hydrogen sorption-desorption and stability to cycling. We synthesized doped derivatives of binary intermetallic compound consisting terbium with cobalt to establish electrochemical properties when using them as anode materials in prototypes of nickel metal hydride batteries. The samples were made of high purity metals in an electric arc furnace in an argon atmosphere. Phase analysis was performed using X-ray diffraction data obtained on the DRON-2.0M powder diffractometer (Fe Kα-radiation). Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescence spectroscopy (XRF) were used to determine the quantitative and qualitative composition of the alloys. Electrochemical hydrogenation was performed in Swagelok cell two-electrode prototypes of chemical sources of electric current on a two-channel MTech G410-2 galvanostat in galvanostatic mode at a current density of 1.0 mA/cm2. The elemental composition of the Tb2Co16.5Sb0.2Li0.3 and Tb2Co16Al0.5Mg0.5 samples before and after hydrogenation was determined by the XRF method, a slight decrease in the content of terbium on the surface was found. Phase analysis of diffractograms of both samples before and after electrochemical hydrogenation showed that they contain hexagonal phases with a stoichiometry of 2:17. Only a phase with a structure of the Th2Ni17 type was found in the Tb2Co16.5Sb0.2Li0.3 alloy. In the Tb2Co16Al0.5Mg0.5 sample, in addition to the main phase with Th2Ni17 structure, the existence of another hexagonal phase with a similar crystal structure (TbCo5-x-yMgxAly) was detected. The results of X-ray diffraction of the Tb2Co16Al0.5Mg0.5 sample are fully consistent with the results of EDX analysis. The Tb2Co16.5Sb0.2Li0.3-based electrode undergoes significant amorphization due to the active hydrogenation/dehydrogenation process, but the hydrogen absorption properties remain acceptable. The cell parameters after hydrogenation increase, which indicates the inclusion of hydrogen atoms into the structure. The amount of deintercalated Hydrogen under experimental conditions is approximately 0.40 H/f.u. The Coulomb efficiency on the 10th cycle is equal to 81.3%, and on the 20th cycle is 90.2%. The Ni-MH battery prototype with the Tb2Co16Al0.5Mg0.5-based electrode demonstrates good reproducibility and Coulomb efficiency. The amount of deintercalated Hydrogen under experimental conditions is approximately 0.44 H/f.u. The Coulomb efficiency on the 10th cycle is 95.5%, and on the 20th is equal to 93.4%. Due to the amorphization processes as the number of cycles increases, the charging plateau voltage increases and a small decrease in the capacitive parameter τ is observed similarly to the Li,Sb-containing electrode. As electrode materials both alloys showed corrosion resistance in the electrolyte solution. Keywords: terbium; cobalt; solid solutions; crystal structure; electrochemical hydrogenation; anode materials.