Search Results (93)

NiMH batteries are the most used technology of rechargeable batteries sold directly to consumers. Herein, we study the performance of the most common sizes of portable NiMH batteries (AA, AAA, D, C, and 9V). The performance and durability parameters—capacity, charge retention, charge recovery, and endurance in cycles—are measured for these types of batteries, according to the standard IEC 61951-2:2017 NiMH batteries. The purpose of this study is to create a basis for setting minimum performance requirements for the parameters in the European Regulation concerning batteries and waste batteries, EU 2023/1542, Annex III, Part B. Results show that the charging time of 16 h could be reduced to 8 h for verifying the rated capacity. The performance of commercial batteries with regard to charge retention, charge recovery, and endurance in cycles is often found to be 25–30% better than required in the relevant IEC standard. Furthermore, we present a short comparative analysis of an application test (IEC 60086-2:2021 “toy”) for portable NiMH batteries with primary batteries. Such data allow comparing the performance of portable NiMH batteries compared to primary batteries in the application test “toy”. Full article

There is a high demand for nickel hydroxide as an engineering material used in the positive electrode of nickel metal hydride (Ni-MH) rechargeable batteries. These batteries are extensively used in various small instruments, disposable batteries, and electric vehicles. The structure of nickel hydroxide significantly influences the discharge capacity and energy density, key properties of Ni-MH batteries, and this structure is primarily determined by the synthesis method used. In this study, nickel hydroxide was synthesized using an electrochemical precipitation method, with current density acting as a parameter to control the desired phase of the product, whether α-nickel hydroxide, β-nickel hydroxide, or a combination of both. At a current density of 50 A/m², the synthesized nickel hydroxide demonstrated a smaller particle size and a superior discharge electrochemical property in comparison to that generated at 500 A/m². The effect of agitation in catholyte was also investigated to examine the change in discharge property of the precipitated material. The product synthesized at 500 A/m² from an agitated catholyte exhibited a tap density of 1.24 g/cc and an improved discharge capacity of 254 mAh per gram of Ni(OH)₂. Full article

In the ongoing shift toward electric vehicles (EVs) primarily utilizing lithium-ion battery technology, a significant population of hybrid electric vehicles (HEVs) remains operational, which are reliant on established NiMH battery systems. Over the last twenty years, these HEVs have generated a substantial number of NiMH batteries that are either inoperable, experiencing performance degradation, or approaching the end of their service life. This situation results in a twofold challenge: (i) a growing volume of environmentally hazardous waste due to the difficulty of NiMH battery reclamation and (ii) escalating maintenance costs for HEV owners necessitated by replacement battery purchases. To overcome this scenario, patent WO2015092107A1, published in 2015, proposed a ‘Method for regenerating NiMH batteries.’ This method claimed the ability to restore NiMH batteries to their original functionality based on a non-intrusive approach. However, a comprehensive review of the relevant scientific literature fails to identify any empirical evidence supporting the efficacy of this regeneration technique. Within this context, this study provides a detailed analysis and evaluation of the regeneration process based on an unsupervised and non-intrusive prototype. The proposed prototype can be used not only to implement and evaluate the previous patent, but also to test any other process or methodology based on controlled charging/discharging periods under certain current conditions. NiMH battery cells from a Toyota Prius were included in this work as a real case study. The experimental results from this prototype demonstrate the reduced potential for battery regeneration using the proposed method. Future contributions should offer a promising solution for mitigating the challenges associated with NiMH battery disposal, maintenance within the HEV domain, and other second-life alternative options. Full article

Mg-based alloy anodes suffer from severe corrosion in alkaline electrolytes, which substantially impedes their cycle life and thereby limits their suitability as anode materials for nickel–metal hydride (Ni-MH) batteries. This work modifies the conventional 6 M KOH electrolyte by adding 0.1 M Al₂(SO₄)₃·18H₂O. The electrochemical hydrogen storage properties of Mg_0.45Ti_0.05Ni_0.50 alloy in this electrolyte and its microstructural evolution during cycling are studied. In the 6 M KOH + 0.1 M Al₂(SO₄)₃·18H₂O electrolyte, a protective layer consisting of Mg₂Al(OH)₇ is formed on the surface of the Mg_0.45Ti_0.05Ni_0.50 alloy anode during charge/discharge cycling instead of Mg(OH)₂, effectively preventing further corrosion and improving its cycle life. The Mg_0.45Ti_0.05Ni_0.50 alloy anode delivers a maximum discharge capacity of 479.0 mAh g⁻¹ and maintains 318.4 mAh g⁻¹ after 30 cycles in the 6 M KOH + 0.1 M Al₂(SO₄)₃·18H₂O electrolyte, which is significantly superior to that achieved in the 6 M KOH electrolyte (471.1 mAh g⁻¹ and 201.8 mAh g⁻¹, respectively). This work provides a new strategy for improving the cycle stability of Mg-based alloy anodes. Full article

The experimental research was focused on the investigation of valuable material from spent Ni-MH type AA batteries, namely the metal grid anodes and the black mass material (anode and cathode powder). The materials of interest were analyzed by X-ray fluorescence spectroscopy (XRF), ICP-OES (inductively coupled plasma optical emission spectrometry), optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The analyzed grids have a high Fe content, but some of them correspond to the Invar alloy with approx. 40% Ni. In the black mass material, round particles and large aggregations were observed by SEM analysis, showing a high degree of degradation. The XRD analysis reveals the presence of only three compounds or phases that crystallize in the hexagonal system: La_0.52Ce_0.33Pr_0.04Nd_0.11Co_0.6Ni_4.4, Ni(OH)₂, and La₅Ni₁₉. The obtained results provide useful and interesting information that can be used for further research in the recycling and economic assessment of metals from spent Ni-MH batteries. Full article

Solar energy is considered the major source of clean and ubiquitous renewable energy available on various scales in electric grids. In addition, solar energy is harnessed in various electronic devices to charge the batteries and power electronic equipment. Due to its ubiquitous nature, the corresponding market for solar-charged small-scale batteries is growing fast. The most important part to make the technology feasible is a portable battery charger and the associated controllers to automate battery charging. The charger should consider the case of charging to be convenient for the user and minimize battery degradation. However, the issue of slow charging and premature battery life loss plagues current industry standards or innovative battery technologies. In this paper, a new pulse charging technique is proposed that obviates battery deterioration and minimizes the overall charging loss. The solar-powered battery charger is prototyped and executed as a practical, versatile, and compact photovoltaic charge controller at cut rates. With the aid of sensor fusion, the charge controller is disconnected and reconnects the battery during battery overcharging and deep discharging conditions using sensors with relays. The laboratory model is tested using a less expensive PV panel, battery, and digital signal processor (DSP) controller. The charging behavior of the solar-powered PWM charge controller is studied compared with that of the constant voltage–constant current (CV–CC) method. The proposed method is pertinent for minimizing energy issues in impoverished places at a reasonable price. Full article

Metallic glasses (MGs) are a type of multicomponent non-crystalline metallic alloys obtained by rapid cooling, which possess several physical, mechanical, and chemical advantages against their crystalline counterparts. In this work, an Fe-based MG is explored as a hydrogen storage material, especially, due to the evidence in previous studies about the capability of some amorphous metals to store hydrogen. The evaluation of an Fe-based MG as a novel negative electrode material for nickel/metal hydride (Ni-MH) batteries was carried out through cyclic voltammetry and galvanostatic charge–discharge tests. A conventional LaNi₅ electrode was also evaluated for comparative purposes. The electrochemical results obtained by cyclic voltammetry showed the formation of three peaks, which are associated with the formation of Fe oxides/oxyhydroxides and hydroxides. Cycling charge/discharge tests revealed activation of the MG electrode. The highest discharge capacity value was 173.88 mAh/g, but a decay in its capacity was observed after 25 cycles, contrary to the LaNi₅, which presents an increment of the discharge capacity for all the current density values evaluated, reached its value maximum at 183 mAh/g. Characterization analyses performed by X-ray diffraction, Scanning Electron Microscopy and Raman Spectroscopy revealed the presence of corrosion products and porosity on the surface of the Fe-based MG electrodes. Overall, the Fe-based MG composition is potentially able to work as a negative electrode material, but degradation and little information about storage mechanisms means that it requires further investigation. Full article

In this paper, a buck DC-DC converter with the proposed twin frequency control scheme (TFCS) and accurate load current sensing (ALCS) was designed and implemented with 0.18 µm CMOS technology for a supply voltage ranging from 2.0 to 3.0 V, which is compatible with state-of-the-art batteries (NiCd/NiMH: 1.1–2 V, Li-Ion: 2.5–4.2 V). The proposed converter yields a peak efficiency of about 92.7% with a load current of 30 mA. Furthermore, it only occupies a silicon area of 1.3 mm². The proposed buck converter is dedicated for smartphone applications whereby it spends most of its time in idle, low load conditions. Full article

This work focuses on the recovery of rare earth elements (REEs = La, Ce, Nd, Pr) from spent nickel–metal hydride batteries by hydrometallurgical processing. The REEs were precipitated in the form of sodium-lanthanide double sulfate salts by adding Na₂SO₄ to a leach liquor prepared from industrially processed spent batteries. The objectives were to better understand the parameters driving the purity of the product and to identify the phases involved, as well as their crystallographic structure. The methodology included experiments performed in a 2 L reactor, thermodynamic calculations and product characterization. We confirmed that high REE precipitation yields (>95%) can be achieved under a wide range of hydrodynamic conditions. Furthermore, we demonstrated and quantified how appropriately washing the product allows for a significant reduction in nickel losses while maintaining control over REE product purity. Finally, using X-ray Diffraction analyses, it was established that REEs form a solid solution with a chemical formula (Na_0.9K_0.1)(La_0.65Ce_0.24Pr_0.04Nd_0.07)(SO₄)₂·H₂O, which has not been reported so far. Full article

This article investigates the impact of loading on the hybrid powertrain of the FCAT-30 model, equipped with a proton-exchange-membrane fuel cell (PEMFC) and a nickel–metal hydride (NiMH) battery. This study involves analyzing structural component performance based on voltage and current measurements of the fuel cell, battery, and powertrain. Tests conducted under different load conditions reveal significant differences in battery current and fuel-cell voltage, highlighting the crucial role of the battery in the powertrain. External loading induces cyclic operation of the fuel cell, generating peak power. The energy balance analysis demonstrates that, under no-load conditions, the vehicle consumes 37.3% of its energy from the fuel cell, with a total energy consumption of 3597 J. Under load, the energy from the battery is significantly utilized, resulting in a constant fuel-cell share of approximately 19%, regardless of the vehicle’s load. This study concludes that the battery predominantly drives the powertrain, with the fuel cell acting as a secondary energy source. These findings provide valuable insights into the power distribution and energy balance in the hybrid powertrain. Using a load driving profile reduced the fuel-cell-stack energy contribution by 6.85% relative to driving without an external load. Full article

The state of charge of a battery depends on many magnitudes, but only voltage and intensity are included in mathematical equations because other variables are complex to integrate into. The contribution of this work was to obtain a model to determine the state of charge with these complex variables. This method was developed considering four models, the multilayer feed-forward backpropagation models of two and three input variables used supervised training, with the variable-learning-rate backpropagation training function, five and seven neurons in the hidden layer, respectively, achieving an optimal training. Meanwhile, the radial basis neural network models of two and three input variables were trained with the hybrid method, the propagation constant with a value of 1 and 80 neurons in the hidden layer. As a result, the radial basis neural network with the variable-learning-rate training function, considering the discharge temperature, was the one with the best performance, with a correlation coefficient of 0.99182 and a confidence interval of 95% (0.98849; 0.99516). It is then concluded that artificial neural networks have high performance when modeling nonlinear systems, whose parameters are difficult to measure with time variation, so estimating them in formulas where they are omitted is no longer necessary, which means an accurate SOC. Full article

Back-scattered electron imaging and X-ray elemental mapping were combined in a tabletop scanning electron microscope (SEM) to investigate cross-sections of three AA-type (mignon) nickel–metal hydride (NiMH) batteries from different manufacturers. All batteries underwent 500–800 charge/discharge cycles and reached their end of lifetime after several years as they could no longer hold any significant electric charge (less than 20% of nominal charge capacity), but none showed any short-circuiting. The types of degradation observed in this field study included electrode swelling, metallic nickel formation and carbon incorporation into pores in the positive electrodes and, in the negative electrodes, metal alloy segregation of different elements such as nickel, lanthanum and, in one case, sodium, as well as grain break-up and pore formation. All these phenomena could readily be observed at rather small magnifications. This will be important for the improvement of NiMH batteries, for which new generations with nominally slightly increased charge capacities are being marketed all the time. Full article

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. Full article

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. Full article

In this paper, we analysed the influence of corrosion processes and the addition of a carbon black-heteropoly phosphomolybdic acid (C45-MPA) nanocomposite on the operating parameters of a hydride electrode obtained on the basis of the intermetallic compound La₂Ni₉Co. The electrochemical properties of negative electrodes for NiMH batteries were studied using galvanostatic charge/discharge curves, the potentiostatic method, and electrochemical impedance spectroscopy (EIS). The morphology and chemical composition analysis of the studied electrodes were investigated by means of scanning electron microscopy (SEM) with supporting energy-dispersive X-ray analysis (EDS). For more structural information, FTIR analysis was performed. The results indicate that the presence of the C45-MPA nanocomposite in the electrode material increased both the discharge capacity of the hydride electrode and the exchange current density of the H₂O/H₂ system. The heteropoly acid-modified electrode is also more resistant to high discharge current densities due to its catalytic activity. Full article