The replacement of expensive metal powders in Ni(OH)₂-based cathodes is essential for reducing cost and environmental impact in aqueous Ni–Zn batteries. This work investigates graphitic wood-derived carbon (GWC) as a sustainable conductive additive to boost the performance of Ni(OH)₂ pasted electrodes prepared by a simple physical mixing process. A number of graphitic wood-derived carbon qualities are explored as functional additives replacing expensive cobalt and nickel powder additives while maintaining the electrochemical performance of Ni(OH)₂ electrodes in aqueous rechargeable Ni–Zn batteries. The GWC offers high electrical conductivity and a unique microsized particulate morphology. Optimizing the GWC content to 25 wt % yields a specific capacity of 284.2 mAh g^–1 at 0.2C, which is better than that of electrodes containing only Ni(OH)₂, with Ni/Co powders, or commercial carbon black. Furthermore, the open-circuit voltage hysteresis and state of charge are studied to understand the charge/discharge process, suggesting that GWC is an effective alternative to expensive metal powders, providing a low-cost and sustainable strategy for improving Ni(OH)₂-based electrodes through a straightforward manufacturing process.

A unique hierarchical S,C-(Cu-PBA/CuS) nanoarray was designed and synthesized through a simple hydrothermal and in-situ vulcanization process. By incorporating the merits of a high theoretical capacity of Cu-based sulfides, a Cu-PBA/CuS heterojunction coated with a polydopamine-derived N-doped carbon layer, homogeneous/heterogeneous surface/interface resulted from in-situ vulcanization process, the S,C-(Cu-PBA/CuS) electrode shows a high specific capacity of 668.5 mAh g⁻¹ at 1 A g⁻¹. Furthermore, the assembled S,C-(Cu-PBA/CuS)//Zn alkaline battery delivers good reversibility for 2000 cycles (capacity retention of 81.3 %) and displays a high energy density of 944 Wh kg⁻¹ at a power density of 1.24 kW kg⁻¹. This structural design strategy provides a feasible scheme for constructing metal sulfides with homojunction/heterojunction structures for high-performance aqueous energy storage and promotes the development of alkaline Cu-Zn batteries and beyond.

Rechargeable aqueous nickel‑zinc (NiZn) batteries have been improved by using a safe low-cost selenized Zn-doped NiMoO₄ (NZO) modified with Prussian blue analogue (PBA). Nanoarray electrodes are explored as possible candidates for high-performance energy storage applications. The unique nanoflake structures improve conductivity and allow for high specific capacitance and reliable cycling stability. In this study, ex-situ XPS and XRD analyses reveal that Ni, Fe, and Se elements are all involved in the electrochemical reactions, and their synergistic effects lead to the composite electrodes exhibiting excellent performance. The optimal electrode has a capacitance of 1.33 F cm⁻² at 0.5 mA cm⁻², which is greater than those of the pristine NZO (0.83 F cm⁻²) and PBA/NZO (0.76 F cm⁻²) electrodes. Furthermore, the assembled NiZn cell can afford a peak energy density of 0.22 mWh cm⁻² and a power density of 19.98 mW cm⁻². This work provides a promising insight into the design and fabrication of nanomaterials of NiZn cathode even beyond for electrochemical energy storage.

Nickel hydroxide electrode materials have been improved for the use in Ni-based rechargeable batteries such as Ni-H₂, NiMH, NiCd, NiFe, and NiZn batteries. A stabilized α-phase Ni_1-xAl_x(OH)₂, synthesized using wet chemical coprecipitation methods while controlling pH accurately followed by hydrothermal treatments at 165 °C, is reported. Variations in synthetic routes, dopants and morphology had strong influence on the electrochemical performance. Morphological control, crystallinity and surface modification by Co(OH)₂ were important for the better performance. Conventional battery grade β-Ni(OH)₂ is usually made of a spherical particles, but we find that circular shaped particles can be advantageous. Hydrothermal treatments increase sample crystallinity and discharge capacity. A hydrothermal treated Ni_0.8Al_0.2(OH)₂-LDH sample reaches a discharge capacity of 368 mAh g⁻¹ and a corresponding Ni_0.9Al_0.1(OH)₂ reaches 405 mAh g⁻¹. Both have a circular-like morphology and the later shows a tap density of 1.52 g cm⁻³ and volumetric energy density of 531 mAh cm⁻³. Only a modest Co(OH)₂ surface coating is needed to reduce the polarization behavior, increase the redox reaction reversibility and electrode kinetics via formation of CoOOH species after electrochemical oxidation.

Addition of oxygen and hydrogen gas batches to a NiMH battery can significantly increase its cycle life. Cycle life has also been extended by the development of more corrosion resistive alloys. Both make the total battery system energy throughput (cycle life × capacity) to reach beyond present Li-batteries. Decreased self-discharge as well as reduced manufacturing cost have been done by eliminating cobalt from the hydrogen storage alloys. A better understanding on how to avoid detrimental species from diffusion between the electrodes has contributed to the positive development and contributed to increase the temperature window wherein NiMH batteries can be operated.

A growth strategy is described where a multidimensional P(Ni, Fe) nanoarray electrode is fabricated by phosphiding NiMoO₄ nanoflakes modified with a Ni-based Prussian blue analogue induced by in situ self-sacrificial formation. The generated electrode exhibits a specific capacity of 501.8 mAh g^–1 at 1 A g^–1, owing to the unique overlapping cross-stacked network structure with increased surface- and interface-active sites and enhanced conductivity. This is about 2 times larger than those of the NiMoO₄ (200.2 mAh g^–1) and NiMoO₄/Ni-Prussian blue analogue (NiMoO₄/Ni-PBA) (217.3 mAh g^–1) electrodes. The battery cell assembled with the obtained P(Ni, Fe) nanoarray electrode and a Zn plate as the counter electrode shows a high energy density of 962.6 Wh kg^–1 at a power density of 870 W kg^–1. This demonstrates the potential of NiMoO₄-based materials for NiZn battery applications and gives insight into the design of electrode materials by controlling the surface/interface in next-generation high-performing NiZn batteries.

In this work, zinc was introduced to prepare Ni1−xZnxMoO4 (0 ≤ x ≤ 1) nanoflake electrodes to increase the energy density and improve the cycling stability for a wider range of applications of aqueous rechargeable nickel-zinc (NiZn) batteries. This was achieved using a facile hydrothermal method followed by thermal annealing, which can be easily scaled up for mass production. Owing to the unique nanoflake structures, improved conductivity, and tunable electronic interaction, excellent electrochemical performance with high specific capacitance and reliable cycling stability can be achieved. When the Zn doping is 25%, the Ni0.75Zn0.25MoO4 nanoflake electrode displays a high specific capacitance of 345.84 mA h g−1 (2490 F g−1) at a current density of 1 A g−1 and improved cycling stability at a high current density of 10 A g−1. NiZn cells assembled with Ni0.75Zn0.25MoO4 nanoflake electrodes and zinc electrodes have a maximum specific capacity of 344.7 mA h g−1 and an energy density of 942.53 W h kg−1. This design strategy for nickel-based electrode materials enables high-performance energy storage and opens up more possibilities for other battery systems in the future.

Spinel oxides with specific morphology are importantly multifunctional materials for various applications. Here we report various morphological spinel oxides with one and two-modal pore size structures. The surface microstructure, phase composition, specific surface areas and electrocatalytic OER/ORR activities are examined. The results reveal that the bicomponent (NiCo₂O₄ and Co₃O₄) spinel exhibits a bimodal pore size distribution, high specific surface area, good OER activity (an overpotential of 313 mV at 10 mA cm⁻²_Geo) and low Tafel slope of 73.1 mV dec⁻¹. The Co₃O₄ component presents a perforated sheet morphology similar to an ancient window configuration with regular hole patterns, which benefits for mass transfer and O₂ bubble detachment. By comparison, the single-component NiCo₂O₄ spinel having the morphology of more open self-assembled nanoneedle spheres or nanorod clusters, similar to the configuration of fish gill filaments, shows better ORR activities. The morphology, similar to the fish gills, can readily capture dissolved oxygen molecules from the film electrolyte at the three-phase interface and improve ORR performance. In addition, calcination temperatures also significantly affect pore structure, surface areas, and electrocatalytic activities. Finally, small Lab size Zn-air cells are assembled using thin flexible air electrodes with the self-assembled nanoneedle NiCo₂O₄ catalysts. Electrochemical charging-discharging performance and cycling durability are evaluated.

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A₂B₇-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La_2-xY_xNi_6.50Mn_0.33Al_0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program - H2TCP Task-40, IEA's expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes.