[en] Highlights: • The occurrence of Li₁₅Si₄ is transient. • The occurring degradation mechanisms depend on the substrate roughness. • Li₁₅Si₄, delamination and reduced coulombic efficiency are related. - Abstract: Silicon is a promising material for negative electrodes in lithium-ion batteries. The degradation of silicon was investigated using thin films between 5 and 50 nm deposited on substrates of varying roughness. We used differential capacity plots to examine the degradation behavior of thin films during cycling. We found that the delamination of the thin films from the substrate depends on the surface roughness and film thickness. The delamination changes the morphology of the thin film and is characterized through the formation of Li₁₅Si₄. The morphology change is also accompanied by reduced coulombic efficiency and an increasing cell polarization. The transient occurrence of Li₁₅Si₄ is explained by the processes during cycling. It may be prevented by stress induced potential suppression which was observed in very thin films as the polarization increases with decreasing layer thickness.

[en] The work described in this paper demonstrates that very small protein and DNA structures can be applied to various substrates without denaturation using aerosol printing technology. This technology allows high-resolution deposition of various nanoscaled metal and biological suspensions. Before printing, metal and biological suspensions were formulated and then nebulized to form an aerosol which is aerodynamically focused on the printing module of the system in order to achieve precise structuring of the nanoscale material on a substrate. In this way, it is possible to focus the aerosol stream at a distance of about 5 mm from the printhead to the surface. This technology is useful for printing fluorescence-marked proteins and printing enzymes without affecting their biological activity. Furthermore, higher molecular weight DNA can be printed without shearing. The advantages, such as printing on complex, non-planar 3D structured surfaces, and disadvantages of the aerosol printing technology are also discussed and are compared with other printing technologies. In addition, miniaturized sensor structures with line thicknesses in the range of a few micrometers are fabricated by applying a silver sensor structure to glass. After sintering using an integrated laser or in an oven process, electrical conductivity is achieved within the sensor structure. Finally, we printed BSA in small micrometre-sized areas within the sensor structure using the same deposition system. The aerosol printing technology combined with material development offers great advantages for future-oriented applications involving biological surface functionalization on small areas. This is important for innovative biomedical micro-device development and for production solutions which bridge the disciplines of biology and electronics.

[en] Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60–90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm–2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390–395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

[en] Highlights: •Ba-substituted LaCoO₃ perovskites prepared by polymerized gel combustion method. •Φ affects the agglomeration grade, compacting, sintering behavior of the perovskites. •ZT-values reach maximum at 400–500 K temperature range. -- Abstract: Structural and thermoelectric transport properties of Ba²⁺ containing lanthanum cobaltate (La_1−xBa_xCoO₃; x = 0.01, 0.03, 0.05) prepared by soft chemistry method were investigated and discussed. The influence of the fuel-to-oxidizer ratio (Φ) of the redox mixture on the powder microstructure was studied. The agglomeration grade of the nanocrystalline perovskite phases can be influenced due to initial composition of the redox mixture. Since the different burning characteristic of the polymerized gels results in different xerogel structures, the as-calcined single phase perovskite samples show different compacting and sintering behavior. The thermoelectric transport properties were measured in the 300–1300 K temperature range. It was found that the electrical and thermal conductivity of the sintered pellets show strong dependence on microstructure. In addition increasing Ba²⁺ content in the samples results in lower thermal conductivity values (κ < 1.5 W/K m). The calculated dimensionless figure of merit (ZT) showed maximum value in the 400–500 K range

[en] Nitrogen-doped TiO₂ catalysts were prepared by a precipitation method. The samples were calcined at 400 deg. C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N₂-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas (a_BET^S) were decreased dramatically. Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400-500 nm wavelength range (λ_g,1=∼390 nm, λ_g,2=∼510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO₂ powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO₂ samples were more catalytically active than non-doped TiO₂ catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO₂ catalysts.

[en] Highlights: • Fabrication of a flexible all solid-state thin film battery. • Impact of dynamic bending on electrochemical and morphological performance. • Electro-chemo-mechanical aging of the battery and its interfaces. • Hindered cathode lithiation kinetics due to mechanical stress and strain. -- Abstract: To design and manufacture high-performance energy storage devices with real mechanical flexibility is one of the main advantages of the solid-state battery technology. Mechanically flexible thin film, all solid-state Li-ion batteries are supposed to be the main power sources in emerging technologies such as flexible electronics, wearables, etc. However, if a flexible solid-state device is exposed to repeated external mechanical load, introducing additional aging mechanisms might be expected. In addition, externally introduced stress and strain to the battery functional components could influence lithiation kinetics of the respective electrode material. In the present study, the effect of the external mechanical load on the lithiation kinetics and the collateral mechanical fatigue of the full battery cell during dynamic bending were investigated in detail. Therefore, mechanically flexible, all solid-state MoO₃/LiPON/Li battery cells were fabricated on a polymer substrate. Battery cells were exposed to static convex bending and it was ascertained that the bulk resistance of the positive electrode is largely dependent on the depth-of-discharge as well as mechanical stress state, while other processes such as charge transfer and electrolyte bulk resistance are less affected. Furthermore, battery cells were cycled galvanostatically, while they were bent repeatedly using different bending scenarios. Below a threshold bending frequency (f = 1/360 Hz), stable battery function was found, however mechanical aging of the battery cell was observed. As it was demonstrated, the metal current collector/positive electrode interface is highly prone to the physical degradation upon dynamic bending. As a result, delamination of the electrode and contact loss occur, causing capacity fading, accordingly. The present study shed light on the joint mechanical-electrochemical aging of mechanically flexible all solid-state Li-ion batteries.

[en] Highlights: • Vanadium redox flow battery utilized for wind power grid integration was studied. • Technical and financial analyses at single wind farm level were performed. • 2 MW/6 MW h VRFB is suitable for mitigating power deviations for a 10 MW wind farm. • Economic incentives might be required in the short-term until the VRFB prices drop. - Abstract: Utilizing a vanadium redox flow battery (VRFB) for better market integration of wind power at a single wind farm level was evaluated. A model which combines a VRFB unit and a medium sized (10 MW) wind farm was developed and the battery was utilized to compensate for the deviations resulting from the forecast errors in an electricity market bidding structure. VRFB software model which was introduced in our previous paper was integrated with real wind power data, power forecasts and market data based on the Spanish electricity market. Economy of the system was evaluated by financial assessments which were done by considering the VRFB costs and the amount of deviation penalty payments resulting from forecast inaccuracies

[en] LiMn₂O₄-films were prepared by air-blast spray pyrolysis directly onto stainless steel foil substrate. The films were synthesized from various precursor solutions of dissolved nitrates and acetates with and without the addition of polyethylene glycol (PEG). Hereby X-ray diffraction experiments revealed that the phase compositions of the as-prepared and thermally post-treated films were highly dependent on the precursors used, but independent of the addition of PEG. Samples prepared from nitrates yielded phase mixtures of α-Mn₂O₃, Mn₃O₄ and LiNO₃ as-prepared and LiMn₂O₄ and α-Mn₂O₃ after post-thermal treatment. Whereas films sprayed from acetate precursors consisted of LiMn₂O₄ predominantly before and after heat treatment, as well. Scanning electron microscopy investigations showed that the applied precursor had an effect on the film morphology and the addition of PEG led to film thinning. Galvanostatic cycling tests and post-mortem analyses of the electrochemical cells fabricated from the thermally treated thin layers revealed that the film prepared from acetates and PEG had the highest capacity retention despite the formation of orthorhombic LiMnO₂ besides the cubic LiMn₂O₄ during battery cycling. - Highlights: • LiMn₂O₄ based Li-ion battery cathode by facile air-blast spray pyrolysis. • Effect of precursor chemistry on crystal phase composition and morphology. • Post-mortem crystallographic and morphological studies of the cathodes. • Morphology of the cathode layer plays essential role in the cycle life behavior of the batteries.