The nickel-iron (Ni-Fe) battery is a century-old technology that fell out of favor compared to modern batteries such as lead–acid and lithium-ion batteries. However, in the last decade, there has been a resurgence of interest because of its robustness and longevity, making it well-suited for niche applications, such as off-grid energy storage systems. Currently, extensive research is focused on addressing perennial issues such as iron passivation and hydrogen evolution reaction, which limit the battery’s energy density, cyclability, and rate performance. Despite efforts to modify electrode composition and morphology, these issues persist, warranting a deeper look at the development story of Ni-Fe battery improvements. In this review, the fundamental reaction mechanisms are comprehensively examined to understand the cause of persisting issues. The design improvements for both the anode and cathode of Ni-Fe batteries are discussed and summarized to identify the promising approach and provide insights on future research directions.

Lithium-ion batteries (LIBs) have circumvented the energy storage landscape for decades. However, safety concerns about liquid–electrolyte-based LIBs have challenged their mobilization. Lithium polymer (LiPo) batteries have gained rising interest due to their high thermal stability. Despite an array of commercially available LiPo batteries, limited studies have ventured into modeling. Numerical simulations allow low-cost optimization of existing battery designs through parameter analysis and material configuration, leading to safer and more energy-efficient batteries. This work examined the electrochemical, thermal, and thermal runaway behavior of a lithium cobalt oxide cathode, graphite anode, and poly(vinylidene fluoride-hexafluoropropylene) electrolyte pouch-type LiPo battery using COMSOL Multiphysics^®, and validated results with experimental data. The simulated potential curve exhibited strong agreement with experiment data, while the temperature profile during discharge displayed qualitative discrepancies rationalized by the reversible heat generation. Thermal runaway simulations via oven tests revealed that the highest heat generation is from the cathode–electrolyte reaction, while the solid electrolyte interface decomposition initiates the heat generation process. These results suggest a thorough selection of cathode and electrolyte material to heighten battery safety. Overall, the developed models can be utilized as design tools to investigate various chemistries and designs to estimate the behavior and performance of batteries.

Sluggish kinetics in oxygen reduction reaction (ORR) requires low-cost and highly durable electrocatalysts ideally produced from facile methods. In this work, we explored the conversion and utilization of waste biomass as potential carbon support for α-MnO₂ catalyst in enhancing its ORR performance. Carbon supports were derived from different waste biomass via hydrothermal carbonization (HTC) at different temperature and duration, followed by KOH activation and subsequent heat treatment. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX) and X-Ray diffraction (XRD) were used for morphological, chemical, and structural characterization, which revealed porous and amorphous carbon supports for α-MnO₂. Electrochemical studies on ORR activity suggest that carbon-supported α-MnO₂ derived from HTC of corncobs at 250 °C for 12 h (CCAC + MnO₂ 250-12) gives the highest limiting current density and lowest overpotential among the synthesized carbon-supported catalysts. Moreover, CCAC + MnO₂ 250-12 facilitates ORR through a 4-e^‑ pathway, and exhibits higher stability compared to VC + MnO₂ (Vulcan XC-72) and 20% Pt/C. The synthesis conditions preserve oxygen functional groups and form porous structures in corncobs, which resulted in a highly stable catalyst. Thus, this work provides a new and cost-effective method of deriving carbon support from biomass that can enhance the activity of α-MnO₂ towards ORR.

The electrooxidation kinetics of ethanol is key to making direct ethanol fuel cells and electrocatalytically reforming ethanol viable technologies for a more sustainable energy conversion. In this study, the electrooxidation of ethanol was investigated on nickel hydroxide (Ni(OH)₂) catalysts synthesized using a facile solvothermal method. Variations in the temperature, heating time, and the addition of oleylamine in the precursor enabled the phase and morphology control of the catalysts. X-ray diffraction and scanning electron microscopy show that the addition of oleylamine in the precursor resulted in microspheres with a high surface area, but favored the formation of β-phase Ni(OH)₂. Elevated temperatures or prolonged periods of heating in a controlled environment, on the other hand, can lead to the formation of the ethanol oxidation reaction-active α-phase. Among the synthesized catalysts, the α-Ni(OH)₂ microspheres with nanoflakes achieved the highest activity for ethanol oxidation with a current density of 24.4 mA cm⁻² at 1.55 V (vs. RHE, reversible hydrogen electrode) in cyclic voltammetry tests and stable at 40 mA cm⁻² in chronoamperometric tests at the same potential, comparatively higher than other Ni-based catalysts found in the literature. While the overpotential is beyond the useful range for direct ethanol fuel cells, it may be useful for understanding the mechanism of ethanol oxidation reactions on transition metal hydroxides at their oxidizing potential for ethanol electroreforming.