Commercial micrometer silicon (Si) powder was investigated as a potential anode material for lithium ion (Li-ion) batteries. The characterization of this powder showed the mean particle size of approx.75.2 nm, BET surface area of 10.6 m^2/g and average pore size of 0.56 nm. Its band gap was estimated to 1.35 eV as determined using UV-Vis diffuse reflectance spectra. In order to increase the surface area and porosity which is important for Li-ion batteries, the starting Si powder was ball-milled and threatened by metal-assisted chemical etching. The mechanochemical treatment resulted in decrease of the particle size from 75 nm to 29 nm, an increase of the BET surface area and average pore size to 16.7 m²/g and 1.26 nm, respectively, and broadening of the X-ray powder diffraction (XRD) lines. The XRD patterns of silver metal-assisted chemical etching (MACE) sample showed strong and narrow diffraction lines typical for powder silicon and low-intensity diffraction lines typical for silver. The metal-assisted chemical etching of starting Si material resulted in a decrease of surface area to 7.3 m²/g and an increase of the average pore size to 3.44 nm. These three materials were used as the anode material in lithium-ion cells, and their electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge-discharge cycles. The enhanced electrochemical performance of the sample prepared by MACE is attributed to increase in pore size, which are large enough for easy lithiation. These are the positive aspects of the application of MACE in the development of an anode material for Li-ion batteries.

We report the effects of thermal oxidation on the sensing properties of porous silicon. Porous silicon substrates were prepared by electrochemical etching and thermally oxidized at different temperatures. A comparative EDS analysis shows that porous surfaces oxidized at higher temperatures have higher oxygen-to-silicon ratios. Our results indicate that the chemoresistive response due to the presence of isopropanol vapors at room temperature also increases with an increasing oxidation temperature. The presence of oxygen atoms in the PS layer could both protect the sensor from further atmospheric oxidation and increase its sensitivity.

The electrode configuration is an important element in the development of Li-ion cells. The energy density is proportional to the loading of the active material. Therefore, increasing the electrode thickness is the simplest way to achieve higher capacities. In this paper, we compare the effects of three different thicknesses of Ag-decorated Si electrode anode (HCSi) on the electrochemical performances such as the SEI layer formation, impedances, and mass capacitances. We prepared three different silicon electrode thicknesses to optimize the electrodes: 20, 40 and 60 µm and measured in situ galvanostatic electrochemical impedance spectroscopy (GEIS). Using GEIS, we studied the intercalation mechanism of Li⁺ ions in detail and found that despite having the same capacities (≈3500 mAh g⁻¹), the thinnest electrode, HCSi20, allows diffusion of Li⁺ ions into the bulk, whereas thicker layers prevent smooth diffusion into the bulk of the silicon electrode due to increased layer resistance. The Voigt model was used to analyze the anomaly of the frequency dependence of the measured impedance, in which, the classical Randles circuit is connected in series with one or two R ‖ C parallel combinations. One R ‖ C circuit could be the result of the SEI formation, and the second R ‖ C circuit could be the contribution of Li. To increase the number of charge and discharge cycles, we improved the electrolyte by adding fluoroethylene carbonate (FEC), which reduced the capacity of the HCSi20 electrode to 50% of the initial capacity (≈3500 mAh g⁻¹) after 60 cycles, whereas it dropped to 20% of the initial capacity after 10 cycles without the addition of FEC.

The dispersion of platinum (Pt) on metal oxide supports is important for catalytic and gas sensing applications. In this work, we used mechanochemical dispersion and compatible Fe(II) acetate, Sn(II) acetate and Pt(II) acetylacetonate powders to better disperse Pt in Fe₂O₃ and SnO₂. The dispersion of platinum in SnO₂ is significantly different from the dispersion of Pt over Fe₂O₃. Electron microscopy has shown that the elements Sn, O and Pt are homogeneously dispersed in α-SnO₂ (cassiterite), indicating the formation of a (Pt,Sn)O₂ solid solution. In contrast, platinum is dispersed in α-Fe₂O₃ (hematite) mainly in the form of isolated Pt nanoparticles despite the oxidative conditions during annealing. The size of the dispersed Pt nanoparticles over α-Fe₂O₃ can be controlled by changing the experimental conditions and is set to 2.2, 1.2 and 0.8 nm. The rather different Pt dispersion in α-SnO₂ and α-Fe₂O₃ is due to the fact that Pt⁴⁺ can be stabilized in the α-SnO₂ structure by replacing Sn⁴⁺ with Pt⁴⁺ in the crystal lattice, while the substitution of Fe³⁺ with Pt⁴⁺ is unfavorable and Pt⁴⁺ is mainly expelled from the lattice at the surface of α-Fe₂O₃ to form isolated platinum nanoparticles.

Rechargeable magnesium batteries suffer a significant overpotential response during galvanostatic cycling often associated with processes at the magnesium/electrolyte interface. These changes cause the system instability, making it difficult to interpret measurements accurately, especially when obtained under uncontrolled conditions, as is often the case in testing of commercial cells. To solve this problem, in this study, we utilized operando electrochemical impedance spectroscopy to investigate the magnesium electrode under nonstationary conditions using the 4D analysis method. This approach enables generation of instant impedance spectra by establishing a mathematical relationship between iso-frequency impedance values and operating time, enabling extrapolation or interpolation of the spectra at any specific moment. Unlike lithium-based systems, where similar corrections have been successfully applied, magnesium systems face unique challenges, primarily due to the divalent nature of Mg ions. These include stronger ion-solvent interactions, sluggish mass transport, and low cation transfer numbers. These factors contribute to potential shifts and instabilities when using Mg metal as a reference electrode. This research focuses on the analysis of the symmetric Mg/Mg cell under galvanostatic and potentiostatic polarization, conditions where nonstationarity is prominent. Continuous impedance measurements taken during these polarizations were used to generate instant spectra through the 4D method. Our goal was to improve the reliability of spectra obtained under nonstationary conditions, paving the way for more accurate online monitoring of battery systems. This, in turn, enhances understanding of electrode/electrolyte processes and supports the development of more stable and efficient rechargeable magnesium batteries.