248 research outputs found
In Situ Investigations of Simultaneous Two-Layer Slot Die Coating of Component-Graded Anodes for Improved High-Energy Li-Ion Batteries
The use of thicker electrodes can contribute to a reduction in cell costs. However, the properties of the electrode must be kept in view to be able to meet the performance requirements. Herein, the possibility of simultaneous multilayer slot die coating is investigated to improve the electrode properties of medium- and high-capacity anodes. The stable coating window of the two-layer slot die coating process is investigated to produce property-graded multilayer electrodes. Electrodes with different styreneâbutadiene rubber (SBR) gradients are investigated with regard to adhesive force and electrochemical performance. An increase in the adhesive force of up to 43.5% and an increase in the discharge capacity is observed
High-Speed Coating of Primer Layer for Li-Ion Battery Electrodes by Using Slot-Die Coating
A reduction of the inactive components can increase the energy density and reduce production cost of Liâion batteries. But an effective reduction of the binder amount also negatively affects the adhesion of the electrode. Herein, slotâdie coating of a primer layer for Liâion anodes is investigated. It is shown that the use of a primer layer with only 0.3âgâm can increase the adhesive force by the factor of 5 as well as the cell performance for anodes with low binder content. The process limits for a stable, defectâfree primer coating are investigated at coating speeds of up to 550âmâmin. The limits coincide both for a setup without vacuum box and with vacuum box with theoryâbased equations. By using a vacuum box, the minimum wet film thickness can be reduced by half
Drying of Lithium-Ion Battery Anodes for Use in High-Energy Cells: Influence of Electrode Thickness on Drying Time, Adhesion, and Crack Formation
Interplane magnetic coupling effects in the multilattice compound Y_2Ba_4Cu_7O_{15}
We investigate the interplane magnetic coupling of the multilattice compound
Y_2Ba_4Cu_7O_{15} by means of a bilayer Hubbard model with inequivalent planes.
We evaluate the spin response, effective interaction and the intra- and
interplane spin-spin relaxation times within the fluctuation exchange
approximation. We show that strong in-plane antiferromagnetic fluctuations are
responsible for a magnetic coupling between the planes, which in turns leads to
a tendency of the fluctuation in the two planes to equalize.
This equalization effect grows whit increasing in-plane antiferromagnetic
fluctuations, i. e., with decreasing temperature and decreasing doping, while
it is completely absent when the in-layer correlation length becomes of the
order of one lattice spacing. Our results provide a good qualitative
description of NMR and NQR experiments in Y_2Ba_4Cu_7O_{15}.Comment: Final version, to appear. in Phys. Rev. B (Rapid Communications),
sched. Jan. 9
Correlative In Situ Multichannel Imaging for Large-Area Monitoring of Morphology Formation in Solution-Processed Perovskite Layers
To scale up production of perovskite photovoltaics, state-of-the-art laboratory recipes and processes must be transferred to large-area coating and drying systems. The development of in situ monitoring methods that provide real-time feedback for process control is pivotal to overcome this challenge. Herein, correlative in situ multichannel imaging (IMI) obtaining reflectance, photoluminescence intensity, and central photoluminescence emission wavelength images on areas larger than 100 cm2 with subsecond temporal resolution using a simple, cost-effective setup is demonstrated. Installed on top of a drying channel with controllable laminar air flow and substrate temperature, IMI is shown to consistently monitor solution film drying, perovskite nucleation, and perovskite crystallization. If the processing parameters differ, IMI reveals characteristic changes in large-area perovskite formation dynamics already before the final annealing step. Moreover, when IMI is used to study >130 blade-coated devices processed at the same parameters, about 90% of low-performing devices contain coating inhomogeneities detected by IMI. The results demonstrate that IMI should be of value for real-time 2D monitoring and feedback control in industrial-scale, high-throughput fabrication such as roll-to-roll printing
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Generation of strength in a drying film: How fracture toughness depends on dispersion properties
The fracture toughness of colloidal films is measured by characterizing cracks which form during directional drying. Images from a confocal microscope are processed to measure the crack width as a function of distance from the crack tip. Applying theory for thin elastic films the fracture toughness is extracted. It is found that the fracture toughness scales with the particle size to the â0.8 power and that the critical energy release rate scales with the particle size to the â1.3 power. In addition, the fracture toughness is found to increase at lower evaporation rates, but the film thickness does not have a significant effect.We thank Professor Bill Clegg for helpful discussions, and Martin Lippert for help with matlab, as well as the Ernest-Solvay-Stiftung and Studienstiftung des deutschen Volkes for financial support of the research visit of N.B.-B. from Karlsruhe Institute of Technology (KIT) to the University of Cambridge
Quasiparticle-quasiparticle Scattering in High Tc Superconductors
The quasiparticle lifetime and the related transport relaxation times are the
fundamental quantities which must be known in order to obtain a description of
the transport properties of the high T_c superconductors. Studies of these
quantities have been undertaken previously for the d-wave, high T_c
superconductors for the case of temperature-independent elastic impurity
scattering. However, much less is known about the temperature-dependent
inelastic scattering. Here we give a detailed description of the
characteristics of the temperature-dependent quasiparticle-quasiparticle
scattering in d-wave superconductors, and find that this process gives a
natural explanation of the rapid variation with temperature of the electrical
transport relaxation rate.Comment: 4 page
A novel slurry concept for the fabrication of Lithium-Ion battery electrodes with beneficial properties
A novel slurry concept for the fabrication of Li-ion battery electrodes focusing on water based formulations is presented. Taking advantage of capillary forces inferred by adding a small fraction of a second fluid immiscible with the bulk continuous phase the low shear viscosity can be varied in a wide range without conventional polymeric rheology control agents disturbing the electric properties of the dry electrode. The new slurries provide superior storage stability and excellent shape accuracy of the final dry film. This reduces waste cut-off at the edges and increases the density of active ingredients, thus improving cost-efficiency. The viscosity at high shear rates remains unaffected, thus the slurries can be processed and coated using established equipment and process parameters. Adhesion to the conductor foil and electrochemical properties of the electrode layers and corresponding cells are similar to those made from conventional slurries
Drying Dynamics of SolutionâProcessed Perovskite ThinâFilm Photovoltaics: In Situ Characterization, Modeling, and Process Control
A key challenge for the commercialization of perovskite photovoltaics is the transfer of highâquality spin coated perovskite thinâfilms toward applying industryâscale thinâfilm deposition techniques, such as slotâdie coating, spray coating, screen printing, or inkjet printing. Due to the complexity of the formation of polycrystalline perovskite thinâfilms from the precursor solution, efficient strategies for process transfer require advancing the understanding of the involved dynamic processes. This work investigates the fundamental interrelation between the drying dynamics of the precursor solution thinâfilm and the quality of the blade coated polycrystalline perovskite thinâfilms. Precisely defined drying conditions are established using a temperatureâstabilized drying channel purged with a laminar flow of dry air. The dedicated channel is equipped with laser reflectometry at multiple probing positions, allowing for in situ monitoring of the perovskite solution thinâfilm thickness during the drying process. Based on the drying dynamics as measured at varying drying parameters, namely at varying temperature and laminar air flow velocity, a quantitative model on the drying of perovskite thinâfilms is derived. This model enables process transfer to industryâscale deposition systems beyond brute force optimization. Via this approach, homogeneous and pinholeâfree blade coated perovskite thinâfilms are fabricated, demonstrating high power conversion efficiencies of up to 19.5% (17.3% stabilized) in perovskite solar cells
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