Lithium–sulfur (Li–S) batteries have attracted much attention due to their high energy density and cost efficiency. However, the drawbacks such as the polysulfide shuttle effect and low electrical ...conductivity of active sulfur material result in poor cycling performance. In this work, we endeavored to overcome these problems by applying a highly engineered bilayer of single-walled carbon nanotubes (SWCNTs). Two monolayers of aligned SWCNTs were deposited on a glass fiber separator using a modified Langmuir–Schaefer method. The deposited bilayer forms a mesh pattern that acts as a spatial filter to mitigate the polysulfide shuttle effect. To confirm the improvement, we assembled cells with modified glass fiber separators coated by SWCNT bilayers and compared their electrochemical performance with unprotected cells with pristine glass fiber separators. The electrochemical results revealed that the discharge capacity increased significantly for the battery with the modified separator. After 50 cycles (0.5 C), the battery with the coated separator had the same discharge capacity as the battery with the pristine separator after only 20 cycles (600 mA h/g), indicating a significant difference of 30 cycles in capacity retention. This implies that an ultrathin bilayer of SWCNTs on the conventional glass fiber separator significantly suppresses the polysulfide shuttle effect.
Few-layer MoS
2
films are promising candidates for applications in numerous areas, such as photovoltaics, photocatalysis, nanotribology, lithium batteries, hydro-desulfurization catalysis and dry ...lubricants, especially due to their distinctive electronic, optical, and catalytic properties. In general, two alignments of MoS
2
layers are possible - the horizontal and the vertical one, having different physicochemical properties. Layers of both orientations are conventionally fabricated by a sulfurization of pre-deposited Mo films. So far, the Mo thickness was considered as a critical parameter influencing the final orientation of MoS
2
layers with horizontally and vertically aligned MoS
2
grown from thin (1 nm) and thick (3 nm) Mo films, respectively. Here, we present a fabrication protocol enabling the growth of horizontally or vertically aligned few-layer MoS
2
films utilizing the same Mo thickness of 3 nm. We show that the sulfur vapor is another parameter influencing the growth mechanism, where a sulfurization with higher sulfur vapor pressure leads to vertical MoS
2
layers and slow sulfur evaporation results in horizontally aligned layers for a thicker Mo starting layer.
Schematic representation of the GIWAXS measurements on HA and VA MoS
2
layers.
We report on a time-resolved study of the colloidal nanoparticle self-assembly into a high-quality nanoparticle crystal with the face-centered cubic crystallographic symmetry. In particular, the ...grazing-incidence small-angle X-ray scattering technique was employed to track kinetics of the solvent evaporation driven self-assembly on casting a drop of plasmonic Ag nanoparticles on a silicon substrate. The short-range (cumulative) disorder typical for paracrystal structures before the complete solvent evaporation at 300–350 s from the drop casting was found with the exception of the time window of 125–150 s where a highly regular transient phase with the long-range order was observed. This temporary improvement of the nanoparticle crystal perfection occurring shortly before the complete solvent evaporation is the main message of the paper. It is attributed to interaction between the surfactant shells of the neighboring nanoparticles getting into contact in the presence of solvent residua to the end of the solvent evaporation which results in a larger nanoparticle hydrodynamic diameter with a smaller dispersion and improvement of the crystallization. This process has direct impact on the quality of the resulting nanoparticle crystal and tailoring its properties.
A high‐performance W/B4C multilayer mirror with 80 periods of nominally 1.37 nm was measured by grazing‐incidence small‐angle X ray scattering (GISAXS) in order to analyse the lateral and vertical ...correlations of the interface roughness within the framework of a scaling concept of multilayer growth. A dynamic growth exponent z = 2.19 (7) was derived, which is close to the value predicted by the Edwards–Wilkinson growth model. The effective number of correlated periods indicates a partial replication of the low interface roughness frequencies. A simulation of the GISAXS pattern based on the Born approximation suggests a zero Hurst fractal parameter H and a logarithmic type of autocorrelation function. The as‐deposited mirror layers are amorphous and exhibit excellent thermal stability up to 1248 K in a 120 s rapid thermal vacuum annealing process. At higher temperatures, the B4C layers decompose and poorly developed crystallites of a boron‐rich W–B hexagonal phase are formed, and yet multilayer collapse is not complete even at 1273 K. Ozone treatment for 3000 s in a reactor with an ozone concentration of 150 mg m−3 results in the formation of an oxidized near‐surface region of a thickness approaching ∼10% of the total multilayer thickness, with a tendency to saturation.
An original diffraction model for the evaluation of the grazing‐incidence small‐angle X‐ray scattering (GISAXS) of the three‐dimensional (3D) supported self‐assembled nanoparticle crystals is ...presented. The model utilizes the formalism of traditional crystallography that is applied to nanoparticles as scattering entities. The infinite paracrystal concept was adopted in order to include cumulative disorder that is typical for the self‐assembled nanoparticle structures. Azimuthal averaging around a chosen crystallographic direction allows incorporation of texture effects. A transformation of the SAXS paracrystal equations to comply with the GISAXS geometry was employed to describe the scattering process in the limit of the kinematical approximation which facilitates calculations. The model was developed for the face‐centered cubic (FCC) symmetry, however, its extension to any other cubic symmetry is straightforward. The model was tested on a 3D nanoparticle assembly formed on silicon from a dried drop‐cast colloidal solution of monodisperse silver nanoparticles of 5.8 ± 0.6 nm diameter. Presence of the FCC nanoparticle crystal with the 111 texture along the substrate normal was evidenced from evaluation of the synchrotron GISAXS data. The degree of paracrystal disorder is 2.5% and 3.6% parallel and perpendicular to the substrate, respectively, suggesting the anisotropic character of the self‐assembling process. A SAXS measurement of the nanoparticle crystal formed from the same solution in a capillary revealed a randomly oriented FCC structure with a slightly larger paracrystal disorder of 4%. Obviously, different conditions of the nanoparticle crystal formation affect its azimuthal and translational disorder.
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