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U.S. patents filed on the topic of nickel/metal hydride (Ni/MH) batteries have been reviewed, starting from active materials, to electrode fabrication, cell assembly, multi-cell construction, system integration, application, and finally recovering and recycling. In each category, a general description about the principle and direction of development is given. Both the metal hydride (MH) alloy and nickel hydroxide as active materials in negative and positive electrodes, respectively, are reviewed extensively. Both thermal and battery management systems (BMSs) are also discussed.

As a desired feedstock for sustainable energy source and for chemical synthesis, the capture and utilization of CO2 have attracted chemists’ continuous efforts. The homogeneous CO2 insertion into a nickel hydride complex to generate formate provides insight into the role of hydrogen as an active hydride form in the hydrogenation of CO2, which serves as a practicable approach for CO2 utilization. To parameterize the activities and to model the structure–activity relationship in the CO2 insertion into nickel hydride, the comprehensive mechanism of CO2 insertion into a series of square planar transition metal hydride (TM–H, TM = Ni, Pd, and Co) complexes was investigated using density functional theory (DFT) computations. The stepwise pathway with the TM-(H)-formate intermediate for the CO2 insertion into all seven square planar transition metal hydride (TM–H) complexes was observed. The overall rate-determining step (RDS) was the nucleophilic attraction of the terminal O atom on the Ni center in Ni-(H)-formate to form Ni-(O)-(exo)formate. The charge of the Ni atom in the axially vacant [Ni]+ complex was demonstrated as the dominant factor in CO2 insertion, which had an excellent linear correction (R2 = 0.967) with the Gibbs barrier (ΔG‡) of the RDS. The parameterized activities and modeled structure–activity relationship provided here light the way to the design of a more efficient Ni–H complex in the capture and utilization of CO2.

The introduction of F‐containing groups into organic molecules can significantly alter their physical and chemical properties. Particularly, gem‐difluoroalkenes serve as versatile precursors for a broad variety of organofluorine compounds, commonly used in agrochemicals, pharmaceuticals, and materials science. Based on the kinetics of H• transfer to acrylamide (kH = 2.28 × 10−4 M−1 s−1 at 300 K in toluene), the study describes a nickel‐hydride‐(or Li[BEt3H]) initiated hydrocyclization/defluorination of CF3‐substituted acrylamides, offering alternative access to 4‐fluorovinyl‐substituted 2‐pyrrolidones (Seletracetam derivatives that are antiepileptic drug candidates). This process proceeds with high yields and remarkable chemo‐ and regioselectivity. The hydrocyclization/defluorination can be initiated by either H• or H– transfer, followed by a 5‐exo‐trig cyclization and subsequent fluorine elimination. The strategy has been applied in the late‐stage functionalization of drug molecules, providing a valuable tool in the synthesis of pharmaceutical compounds. The study develops a H•/H– transfer strategy enabling efficient hydrocyclization/defluorination of CF3‐acrylamides to synthesize Seletracetam derivatives with gem‐difluoroalkenes. Mechanistic studies reveal distinct pathways: the NiII‐H/PhSiH3 system operates through a hydrogen atom transfer process, while the 1,4‐Michael addition of H– appears to be responsible for the Li[BEt3H] system.

Cracks are induced during hydrogen charging in Nickel. We have reported that the cracks initiate near the boundary between nickel matrix and nickel hydride formed near the surface by hydrogen charging. The driving force is considered to be residual stress caused by hydride formation. In the present paper, the stress distribution has been calculated near the boundary using Finite element method to clarify the crack initiation mechanism. As a result, the high-stress area corresponded to the area where the cracks were observed in the experiment.

There is still much to be learned about the properties of siderophores and their applications. This study was designed to characterize and optimize the production of the siderophore produced by a marine bacterium Pseudomonas sp. strain ASA235 and then evaluate their use in bioleaching of rare earth elements (REEs) from spent Nickel–metal hydride (NiMH) batteries. The results of both Tetrazolium and Arnowʼs tests indicated that the test organism produces a mixed-type siderophore of pyoverdine family, a result that was confirmed by FT-IR and MALDI-TOFF analyses. Optimization of pH, temperature, incubation period, and iron concentration for siderophore production led to a noticeable shift from 44.5% up to 91% siderophore unit when the test bacterium was incubated at 28 °C and pH 7 after 72 h in the absence of iron. The purified siderophore showed the ability to bleach about 14.8% of lanthanum from the anode of the NiMH battery along with other elements, although in lower amounts. This data put siderophores in distinct focus for further prospective studies intending the bioleaching of such precious elements. The scaling up of this process and optimization would make a big difference in such a green bioleaching strategy, allowing us to recover such precious elements in an environmentally friendly way.

Minimizing e-waste by extracting valuable parts or by utilizing them for the development of devices can be a productive way to manage it. The present research work focusses on the use of electrochemically modified steel mesh (SM) extracted from discarded nickel-metal hydride (Ni-MH) batteries for the application of energy generation. Upon deposition of amorphous nickel selenide film on SM, significant activity towards catalysing the urea oxidation reaction (UOR) is reported. Electrodeposition of Nickel selenide on SM was confirmed by analytical techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and EDX studies. Electrochemical studies reveal that for NiSe@SM a potential of 1.375 V vs RHE is needed to obtain a current density of 10 mA cm −2 , which is significantly higher than the noble metal-based mixed metal oxide (MMO) catalyst. Further, the NiSe@SM showed minimum Tafel slope of 47 mV dec −1 and exhibited minimum charge transfer resistance among all the tested films. Furthermore, the film showed stability of 9 h confirming the robustness of catalyst. The findings indicate that the inclusion of Selenium led to an improvement in the activity and kinetics of the UOR. This research lays the groundwork for developing environmentally acceptable electrode materials from electronic waste for generating sustainable energy. Graphical abstract

An alternative route for metal hydrogenation has been investigated: cold plasma hydrogen implantation on polyol-made transition metal nanoparticles. This treatment applied to a challenging system, Ni–H, induces a re-ordering of the metal lattice, and superstructure lines have been observed by both Bragg–Brentano and grazing incidence X-ray diffraction. The resulting intermetallic structure is similar to those obtained by very high-pressure hydrogenation of nickel and prompt us to suggest that plasma-based hydrogen implantation in nanometals is likely to generate unusual metal hydride, opening new opportunities in chemisorption hydrogen storage. Typically, almost isotropic in shape and about 30 nm sized hexagonal-packed Ni2H single crystals were produced starting from similarly sized cubic face-centred Ni polycrystals.

Current AB 5 -type hydrogen storage alloys employed in nickel-metal hydride (NiMH) batteries exhibit exceptional low-temperature discharge performance but suffer from limited cycle life and insufficient high-temperature stability. To overcome these challenges, we introduce a hydrothermal synthesized LaF 3 coating layer on the surface of the AB 5 anode material. This LaF 3 coating layer adds a protective barrier for the active material, significantly improving the battery’s cycle life and high-temperature stability. Our findings indicate that (1) the LaF 3 coated anode demonstrates an extended cycle life with increased specific capacity and a capacity retention of 88% after 40 cycles of abusive overcharging and rapid discharging at room temperature. (2) The synthesized anode exhibits a 97% recovery of its specific capacity of 292.7 mAh/g following 144 h of high-temperature storage. (3) The low-temperature discharge capacity of the synthesized anode remains on par with the pristine AB 5 alloy at 230.4 mAh/g in a −40 °C environment. This research presents a significant advancement in hydrogen storage alloy coatings and offers valuable insights for designing electrodes in NiMH batteries.

Nowadays, due to the increasing use of electric vehicles, manufacturers are making more and more innovations in the batteries used in electromobility, in order to make these vehicles more efficient and provide them with greater autonomy. This has led to the need to evaluate and compare the efficiency of different batteries used in electric vehicles to determine which one is the best to be implemented. This paper characterises, models and compares three batteries used in electromobility: lithium-ion, lead-acid, and nickel metal hydride, and determines which of these three is the most efficient based on their state of charge. The main drawback to determine the state of charge is that there are a great variety of methods and models used for this purpose; in this article, the Thévenin model and the Coulomb Count method are used to determine the state of charge of the battery. When obtaining the electrical parameters, the simulation of the same is carried out, which indicates that the most efficient battery is the Lithium-ion battery presenting the best performance of state of charge, reaching 99.05% in the charging scenario, while, in the discharge scenario, it reaches a minimum value of 40.68%; in contrast, the least efficient battery is the lead acid battery, presenting in the charging scenario a maximum value of 98.42%, and in the discharge scenario a minimum value of 10.35%, presenting a deep discharge. This indicates that the lithium-ion battery is the most efficient in both the charge and discharge scenarios, and is the best option for use in electric vehicles. In this paper, it was decided to use the Coulomb ampere counting method together with the Thévenin equivalent circuit model because it was determined that the combination of these two methods to estimate the SOC can be applied to any battery, not only applicable to electric vehicle batteries, but to battery banks, BESS systems, or any system or equipment that has batteries for its operation, while the models based on Kalman, or models based on fuzzy mathematics and neural networks, as they are often used and are applicable only to a specific battery system.

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.