Lithium-ion (Li-ion) batteries with Ni-based cathodes are leading storage technology in the fields of electric vehicles and power-grid applications. NCA (LiNiCoAlO₂) batteries are known for their troublesome degradation tendencies, and this susceptibility to degradation raises questions regarding the safety of their usage. Hence, it is of vital importance to analyse the degradation of NCA batteries via methods which are applicable to onboard systems, so that the changes in the battery’s state of health can be addressed accordingly. For this purpose, it is crucial to study batteries stressed by various conditions which might induce degradation of different origins or magnitudes. Methods such as electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and incremental capacity analysis (ICA) have been used in battery research for years, however, there is a lack of published studies which would analyse the degradation of NCA batteries by simultaneous usage of these methods, which is essential for a comprehensive and confirmatory understanding of battery degradation. This study intends to fill this research gap by analysing the degradation of NCA batteries via simultaneous usage of EIS, GITT, and ICA methods for common stress-inducing operating conditions (over-charge, over-discharge, and high-current charging).

Nickel-based sulfides (particularly NiS₂) are regarded as promising materials for highly efficient electrochemical generation and storage devices. The conventional fabrication methods of nanostructured NiS_X electrodes involve several complex steps using multiple precursors and techniques. In this paper, the NiS_X electrodes are prepared by a plain one-step process of one-zone sulfurization of Ni foam. The evolution of highly electroactive 2D-nanoflakes reliant on sulfurization temperature is studied. Scanning electron microscopy, x-ray diffractometry, and energy-dispersive x-ray spectroscopy confirmed the presence of NiS_X (x = 1 and 2) in the prepared structures. A strong dependence of sample morphology and 2D-nanoflakes density on sulfurization temperature was demonstrated. The electrochemical properties of samples were characterized by cyclic voltammetry and electrochemical impedance spectroscopy measurements. Owing to the 2D-nanoflake structure, the NiS₂ showed attractive electrochemical performance, including a high specific capacitance of 648 mF cm⁻² and a capacitance retention rate of 90,7% after 3000 cycles. Our study shows that the composition and crystal growth of NiS_X can be tuned by reaction temperature during the sulfurization and high perspective of sulfurization in the synthesis of highly electroactive large-scale electrodes for supercapacitors.

The transition to a green economy is becoming an important challenge for sustainable economic growth

The paper presents fabrication and characterization of amorphous silicon carbide (a-SiC:H) based structures for photo-electrochemical (PEC) water splitting. The increase of the photocurrent of PEC upon the decreased of CH ₄ flow during the deposition is associated with the decrease of the band gap and increased absorption of light in a-SiC:H. Photocurrent of 50 µ A/cm ² is achieved for PEC structure prepared with the lowest CH ₄ flow during the deposition. An ITO/a-SiC:H/Si silicon heterojunction structure forming a simple photovoltaic cell (PV) with efficiency of 9.66% was prepared to support additional voltage hereby forming a hybrid PEC-PV system. ASA simulation revealed that a photocurrent of 0.62 mA/cm ² and solar to hydrogen efficiency of 0.76% can be achieved for hybrid a PEC-PV structure with 5 PVs connected in series behind the PEC cell. Further opportunities for increasing the performance are discussed and summarized.

Supercapacitors are vital for modern energy storage systems due to their high power density and long operational lifespan. In this study, we investigate the use of molybdenum trioxide (MoO₃) microstructures for supercapacitor applications. MoO₃ exhibits favourable properties such as low serial resistance, high conductivity, and the possibility of high surface area. These properties enhance the overall electrochemical performance of such supercapacitors. The study focuses on optimizing MoO₃ preparation via oxidation at various temperatures. It was found that the orthorhombic phase of MoO₃, formed at 500 °C, provided the best performance with a specific capacitance of 179.2 F/g (933 mF/cm²) and the lowest serial resistance. Furthermore, the chemical activation of the surface by immersion in 1 M potassium hydroxide significantly increased the surface area, as confirmed by scanning electron microscopy. This hydroxide activation also led to a rise in specific capacitance, reaching 201.7 F/g (902 mF/cm²). The findings presented in this work suggest that the combination of optimal oxidation conditions and surface activation via KOH immersion can lead to enhanced energy storage capacity in such supercapacitor structures. Graphical abstract

The self-decomposition reaction of the nickel ammonia complex was used for the nickel hydroxide formation on the nickel foam with further modification in several ways. The addition of polyvinyl pyrrolidone (PVP) and the electrochemical or chemical activation with cobalt hydroxide was used to modify the formation method. In all cases, structures with Ni(OH)₂ nanoflakes were formed. It was found that the flower-like particles of Co(OH)₂ were precipitated during chemical activation among the nanoflakes. It was shown that the presence of PVP during the nickel ammonia complex decomposition suppressed the highly branched particles. The absence of the highly branched particles increased the capacitive properties of the formed electrode at high current densities. The highest capacitance in 1408 F/g at 1 A/g was shown for the sample precipitated with the PVP presence and the further chemical activation by cobalt.