Solid‐state sodium batteries (SSNBs) have attracted extensive interest due to their high safety on the cell level, abundant material resources, and low cost. One of the major challenges in the ...development of SSNBs is the suppression of sodium dendrites during electrochemical cycling. The solid electrolyte Na3.4Zr2Si2.4P0.6O12 (NZSP) exhibits one of the best dendrite tolerances of all reported solid electrolytes (SEs), while it also shows interesting dendrite growth along the surface of NZSP rather than through the ceramic. Operando investigations and in situ scanning electron microscopy microelectrode experiments are conducted to reveal the Na plating mechanism. By blocking the surface from atmosphere access with a sodium‐salt coating, surface‐dendrite formation is prevented. The dendrite tolerance of Na | NZSP | Na symmetric cells is then increased to a critical current density (CCD) of 14 mA cm−2 and galvanostatic cycling of 1 mA cm−2 and 1 mAh cm−2 (half cycle) is demonstrated for more than 1000 h. Even if the current density is increased to 3 mA cm−2 or 5 mA cm−2, symmetric cells can still be operated for 180 h or 12 h, respectively.
Fast Na‐dendrite growth along the surface of Na3.4Zr2Si2.4P0.6O12 (NZSP) rather than through the ceramic is observed. Atmosphere and surface‐coating influence the surface‐dendrite growth on NZSP. After coating the NZSP surface with a protective layer, the critical current density of the Na | NZSP | Na symmetric cells increases up to 14 mA cm−2. The cell withstands galvanostatic cycling with 1 mA cm−2 and 1 mAh cm−2 for 1000 h.
“Anode‐free” solid‐state battery concepts are explored extensively as they promise a higher energy density with less material consumption and simple anode processing. Here, the homogeneous and ...uniform electrochemical deposition of alkali metal at the interface between current collector and solid electrolyte plays the central role to form a metal anode within the first cycle. While the cathodic deposition of lithium has been studied intensively, knowledge on sodium deposition is scarce. In this work, dense and uniform sodium layers of several microns thickness are deposited at the Cu|Na3.4Zr2Si2.4P0.6O12 interface with high reproducibility. At current densities of ≈1 mA∙cm−2, relatively uniform coverage is achieved underneath the current collector, as shown by electrochemical impedance spectroscopy and 3D confocal microscopy. In contrast, only slight variations of the coverage are observed at different stack pressures. Early stages of the sodium metal growth are analyzed by in situ transmission electron microscopy revealing oriented growth of sodium. The results demonstrate that reservoir‐free (“anode‐free”) sodium‐based batteries are feasible and may stimulate further research efforts in sodium‐based solid‐state batteries.
The cathodic deposition of sodium at the Cu|Na3.4Zr2Si2.4P0.6O12 interface aiming for “reservoir‐free” sodium solid‐state batteries is studied systematically. Dense and roughly 10 µm thick sodium layers are formed underneath the copper current collector. By increasing the current density j during deposition, a higher coverage is obtained, while the stack pressure has only a minor influence on the coverage.
In recent years, many efforts have been made to introduce reversible alkali metal anodes using solid electrolytes in order to increase the energy density of next‐generation batteries. In this ...respect, Na3.4Zr2Si2.4P0.6O12 is a promising solid electrolyte for solid‐state sodium batteries, due to its high ionic conductivity and apparent stability versus sodium metal. The formation of a kinetically stable interphase in contact with sodium metal is revealed by time‐resolved impedance analysis, in situ X‐ray photoelectron spectroscopy, and transmission electron microscopy. Based on pressure‐ and temperature‐dependent impedance analyses, it is concluded that the Na|Na3.4Zr2Si2.4P0.6O12 interface kinetics is dominated by current constriction rather than by charge transfer. Cross‐sections of the interface after anodic dissolution at various mechanical loads visualize the formed pore structure due to the accumulation of vacancies near the interface. The temporal evolution of the pore morphology after anodic dissolution is monitored by time‐resolved impedance analysis. Equilibration of the interface is observed even under extremely low external mechanical load, which is attributed to fast vacancy diffusion in sodium metal, while equilibration is faster and mainly caused by creep at increased external load. The presented information provides useful insights into a more profound evaluation of the sodium metal anode in solid‐state batteries.
The interfacial stability and the dissolution kinetics under external current load of a Na3.4Zr2Si2.4P0.6O12 solid electrolyte in contact with sodium metal are systematically studied. Beside the formation of a kinetically stabilized interphase, current constriction is identified as a dominating process at the interface. After anodic dissolution a pronounced equilibration of the formed interfacial morphology is observed at resting conditions.
In recent years, all‐solid‐state batteries (ASSBs) with metal anodes have witnessed significant developments due to their high energy and power density as well as their excellent safety record. While ...intergranular dendritic lithium growth in inorganic solid electrolytes (SEs) has been extensively studied for lithium ASSBs, comparable knowledge is missing for sodium‐based ASSBs. Therefore, polycrystalline Na‐β″‐alumina is employed as a SE model material to investigate the microstructural influence on sodium filament growth during deposition of sodium metal at the anode. The research focuses on the relationship between the microstructure, in particular grain boundary (GB) type and orientation, sodium filament growth, and sodium ion transport, utilizing in situ transmission electron microscopy (TEM) measurements in combination with crystal orientation analysis. The effect of the anisotropic sodium ion transport at/across GBs depending on the orientation of the sodium ion transport planes and the applied electric field on the current distribution and the position of sodium filament growth is explored. The in situ TEM analysis is validated by large field of view post‐mortem secondary ion mass spectrometer (SIMS) analysis, in which sodium filament growth within voids and along grain boundaries is observed, contributing to the sodium network formation potentially leading to failure of batteries.
The critical role of anisotropic ion transport in solid electrolytes ! Knowledge of the intergranular dendritic growth of sodium in inorganic solid electrolytes is still lacking, especially the effect of the anisotropic ion transport due to the microstructure. It can lead to filament growth and blockade of ion transport at/across specific grain boundaries.
Sophisticated IrO2(110)‐RuO2(110)/Ru(0001) model electrodes are employed in the oxygen evolution reaction (OER) under acidic conditions. The potential‐induced pitting corrosion of such electrodes is ...confirmed by a variety of experimental techniques, including scanning electron microscopy (SEM), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), and operando scanning flow cell‐inductively coupled plasma mass spectrometry (SFC‐ICP‐MS). The structure of the pits is reminiscent of a cylinder (evidenced by focused ion beam scanning electron microscopy: FIB‐SEM), where the inner surface of the pits is covered by hydrous RuO2 (cyclic voltammetry, ToF‐SIMS) that is formed by electrochemical oxidation of the metallic Ru(0001) substrate. The time evolution of the corrosion process at a fixed electrode potential (1.48 V vs. SHE) is followed via cyclic voltammetry and SEM. The passivating IrO2(110) layer results in an “induction period” for the pit growth that is followed by rapid corrosion of the RuO2(110)/Ru(0001) substrate. The observed narrow and time‐independent size distribution relative to the mean size of the pits is attributed to a sluggish removal of the corrosion products by diffusion across the cracks of the pits covering IrO2 layer, leading to steady state corrosion during a total polarization time of 20 to 60 minutes.
Meet in the pit: Anodic corrosion of IrO2(110)‐RuO2(110)/Ru(0001) model electrodes in the potential region of the oxygen evolution reaction leads to potential‐induced pits that are covered by hydrous RuO2 and is visualized in three dimensions.
Abstract
Sophisticated IrO
2
(110)‐RuO
2
(110)/Ru(0001) model electrodes are employed in the oxygen evolution reaction (OER) under acidic conditions. The potential‐induced pitting corrosion of such ...electrodes is confirmed by a variety of experimental techniques, including scanning electron microscopy (SEM), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), and operando scanning flow cell‐inductively coupled plasma mass spectrometry (SFC‐ICP‐MS). The structure of the pits is reminiscent of a cylinder (evidenced by focused ion beam scanning electron microscopy: FIB‐SEM), where the inner surface of the pits is covered by hydrous RuO
2
(cyclic voltammetry, ToF‐SIMS) that is formed by electrochemical oxidation of the metallic Ru(0001) substrate. The time evolution of the corrosion process at a fixed electrode potential (1.48 V vs. SHE) is followed via cyclic voltammetry and SEM. The passivating IrO
2
(110) layer results in an “induction period” for the pit growth that is followed by rapid corrosion of the RuO
2
(110)/Ru(0001) substrate. The observed narrow and time‐independent size distribution relative to the mean size of the pits is attributed to a sluggish removal of the corrosion products by diffusion across the cracks of the pits covering IrO
2
layer, leading to steady state corrosion during a total polarization time of 20 to 60 minutes.
The photomotor response (PMR) of zebrafish embryos, a light pulse-triggered undirected movement, is known to be altered by neuroactive chemicals. Here, we developed an approach for data analysis of ...the distribution of PMR movement activities along the time axis; differences between treatment and respective controls are expressed by an aggregated value integrating the time-resolved density of the movement parameter as a measure for a chemically elicited PMR effect. Logistic concentration-PMR effect relationships were modeled for neuroactive test compounds with different modes of action (acetylcholinesterase inhibition, activation and inhibition of voltage-gated sodium channels); 50% effect concentrations (EC50) were in the low to medium μM range (EC50 < 10 μM for flucythrinate, esfenvalerate, azinphos-methyl, propoxur; EC50 > 10 μM for tricaine). Modulation of movement activities in different phases of the PMR (i.e., “fingerprint”) by neuroactive test compounds varied across concentrations, showing that mode of action-specific PMR fingerprints are also concentration-dependent. Above concentrations causing 10% lethality (LC10; 48 h), 3,4-dichloroaniline caused movement inhibition. This substance presumably is not neuroactive; its effect on the PMR therefore is considered a secondary toxic effect. Quantitative morphological examinations of chemically exposed embryos showed that malformations occurred only above PMR effect concentrations, indicating that changes in the PMR were not due to such indirect effects. The PMR assay will provide a useful measure in ecotoxicological risk assessment of neuroactive chemicals with zebrafish embryos and could potentially be used to infer acute fish toxicity levels from PMR effect concentrations of neurotoxic compounds.
authoren Organic solar cells are a promising technology for a large area conversion of sunlight into electricity. In particular for solar cells based on oligomers (small molecules), efficient donor ...materials absorbing wavelengths larger than 780 nm are still rare. Here, we investigate three aza‐BODIPY dyes absorbing in the infrared. The addition of side groups leads to a red shift of the optical gap from 802 to 818 nm. In optimized devices using these donors in a bulk heterojunction with C60, we observe a higher charge carrier mobility and a higher power conversion efficiency for the molecules without a methyl or methoxy side group lowering the molecular reorganization energy. Surprisingly, the donor–acceptor blend with the lowest energy loss during the electron transfer to the C60 yields the highest short circuit current. With increasing size of the attached side chain, the devices exhibit a larger trap density, measured by impedance spectroscopy. Based on the investigation of different blend ratios, we conclude that these traps are mainly present in the donor phase.
Många elever upplever att matematik är ett svårt ämne, detta kan bli ännu svårare för flerspråkiga elever. Forskning påvisar att språksvårigheter är en bidragande faktor för flerspråkiga elever när ...de läser text- och problemlösningsuppgifter. Det är viktigt att ta reda på vilka hinder flerspråkiga elever kan stöta på i matematikundervisningen, samt hur lärarna kan stötta dem. Syftet med den här kunskapsöversikten är att analysera tidigare forskning som undersöker om problemlösningsuppgifter i matematik kan vara ett hinder för flerspråkiga elever. Olika sökord användes i databaserna Primo och Eric (ProQuest) för att hitta de valda vetenskapliga artiklarna. Begränsningar gjordes genom att välja peer reviewed och publikationsår. De åtta valda vetenskapliga artiklarna kartlades för att få övergripande förståelse av innehållet. För att besvara syftet utgick vi från två frågeställningar: Vad säger forskningen om problemlösningsuppgifter i matematik för flerspråkiga elever? Vilka strategier kan lärare tillämpa i undervisningen? Resultaten visar att flerspråkiga elever har svårigheter i matematik där text- och problemlösningsuppgifter förekommer. Resultaten visar att det finns olika strategier och metoder som lärarna kan tillämpa i undervisningen för att stödja flerspråkiga elever. Matematiklärare kan dra nytta av resultatet i kunskapsöversikten och tillämpa det i undervisningen.
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