Overcoming Anode Instability in Solid-State Batteries through Control of the Lithium Metal Microstructure

Enabling the lithium metal anode (LMA) in solid-state batteries (SSBs) is the key to developing high energy density battery technologies. However, maintaining a stable electrode–electrolyte interface presents a critical challenge to high cycling rate and prolonged cycle life. One such issue is the interfacial pore formation in LMA during stripping. To overcome this, either higher stack pressure or binary lithium alloy anodes are used. Herein, it is shown that fine-grained (d = 20 µm) polycrystalline LMA can avoid pore formation by exploiting the microstructural dependence of the creep rates. In a symmetric cell set-up, i.e., LiǀLi_6.25Al_0.25La₃Zr₂O₁₂(LLZO)ǀLi, fine-grained LMA achieves > 11.0 mAh cm⁻² compared to ≈ 3.6 mAh cm⁻² for coarse-grained LMA (d = 295 µm) at 0.1 mA cm⁻² and at moderate stress of 2.0 MPa. Smaller diffusion lengths (≈ 20 µm) and higher diffusivity pathway along dislocations (D_d ≈ 10⁻⁷ cm² s⁻¹), generated during cell fabrication, result in enhanced viscoplastic deformation in fine-grained polycrystalline LMA. The electrochemical performances corroborate well with estimated creep rates. Thus, microstructural control of LMA can significantly reduce the required stack pressure during stripping. These results are particularly relevant for “anode-free” SSBs wherein both the microstructure and the mechanical state of the lithium are critical parameters.     

Two-channel switched reluctance starter/generator results

Measured data and simulation results for a two-channel experimental switched-reluctance-motor (SRM)-based aircraft engine starter/generator system are presented. The two channels of the system provide power to two separate and independent loads. The results presented document the performance capability of this system with both channels operating simultaneously. Both measured and predicted system performance are presented and compared. In addition, operating characteristics that are unique to this SRM-based system are described. Of particular interest are the interactions between the two separate channels when one channel experiences a load transient and the other channel does not. The source of channel interactions is described, and measured data is provided. The issue of clearing load faults is also addressed. Design results for adding this capability to the experimental system are described     

Electrogenerated chemiluminescence. 58. Ligand-sensitized electrogenerated chemiluminescence in europium labels

The electrochemistry and electrogenerated chemiluminescence (ECL) of a series of europium chelates, cryptates, and mixed-ligand chelate/cryptand complexes were studied. The complexes were of the following general forms: EuL(4)(-), where L = β-diketonate, a bis-chelating ligand (such as dibenzoylmethide), added as salts (A)EuL(4), where A = tetrabutylammonium ion or piperidinium ion (pipH(+)); Eu(crypt)(3+), where crypt = a cryptand ligand, e.g., 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8,8,5]tricosane; and Eu(crypt)(L)(2+) for the mixed-ligand systems. ECL was obtained for the chelates and mixed-ligand systems by reducing the complexes at a Pt electrode in the presence of peroxydisulfate in acetonitrile solutions and was attributed to the electron-transfer reaction between the reduced bound ligands and SO(4)(?)(-), followed by intramolecular excitation transfer from the excited ligand orbitals to the metal-centered 4f states. No ECL was observed under the same conditions for the europium complexes incorporating only the cryptand ligands in aqueous solution. The ECL spectra matched the photoluminescence spectra with a narrow emission band observed at 612 nm, corresponding to a metal-centered 4f-4f transition. The ECL efficiencies for the ECL-active species were low, about 10(-)(1)-10(-)(4)% of that of the Ru(bpy)(3)(2+)/S(2)O(8)(2)(-) system under similar conditions.     

Packing-density calculation of thin fluoride films from infrared transmission spectra

Optical thin films of MgF(2) and NdF(3) have been made by molecular-beam deposition in ultrahigh vacuum. The film packing density was calculated from the water amount that filled the cavities of the films in air. For that the transmission in the IR spectral region with a characteristic water absorption band at a wave number of 3400 cm(-1) was measured. The influence on the packing density of a modification of thin-film morphology by stratification of very thin sublayers of different crystallizing fluorides is tested.     

Antireflection coatings for UV radiation obtained by molecular-beam deposition

We have developed fluoride antireflection (AR) coatings on MgF(2) substrates for a wavelength of 248 nm by molecular-beam deposition. Transmission and laser-induced damage threshold of the samples were measured and atomic force microscope (AFM) investigations were carried out. We compare a 14-layer design for AR coatings with sublayer thicknesses of 12 nm with a conventional two-layer design with quarter-wavelength thicknesses. The laser-induced damage threshold of the 14-layer coating is slightly higher than that of the two-layer coating. The AFM surface images show that the 14-layer coating has a smoother surface than the two-layer coating.     

Virtual worlds as knowledge management platform – a practice‐perspective

Virtual worlds, as electronic environments where individuals can interact in a realistic manner in form of avatars, are increasingly used by gamers, consumers and employees. Therefore, they provide opportunities for reinventing business processes. Especially, effective knowledge management (KM) requires the use of appropriate information and communication technology (ICT) as well as social interaction. Emerging virtual worlds enable new ways to support knowledge and knowing processes because these virtual environments consider social aspects that are necessary for knowledge creating and knowledge sharing processes. Thus, collaboration in virtual worlds resembles real‐life activities. In this paper, we shed light on the use of Second Life (SL) as a KM platform in a real‐life setting. To explore the potential and current usage of virtual worlds for knowledge and knowing activities, we conducted a qualitative study at IBM. We interviewed IBM employees belonging to a special workgroup called ‘Web 2.0/virtual worlds’ in order to gain experience in generating and exchanging knowledge by virtually collaborating and interacting. Our results show that virtual worlds – if they are able to overcome problems like platform stability, user interface or security issues – bear the potential to serve as a KM platform. They facilitate global and simultaneous interaction, create a common context for collaboration, combine different tools for communication and enhance knowledge and knowing processes.     

Knowledge based quality-driven architecture design and evaluation

Modelling and evaluating quality properties of software is of high importance, especially when our every day life depends on the quality of services produced by systems and devices embedded into our surroundings. This paper contributes to the body of research in quality and model driven software engineering. It does so by introducing; (1) a quality aware software architecting approach and (2) a supporting tool chain. The novel approach with supporting tools enables the systematic development of high quality software by merging benefits of knowledge modelling and management, and model driven architecture design enhanced with domain-specific quality attributes. The whole design flow of software engineering is semi-automatic; specifying quality requirements, transforming quality requirements to architecture design, representing quality properties in architectural models, predicting quality fulfilment from architectural models, and finally, measuring quality aspects from implemented source code. The semi-automatic design flow is exemplified by the ongoing development of a secure middleware for peer-to-peer embedded systems.     

Stream engines meet wireless sensor networks: cost-based planning and processing of complex queries in AnduIN

Wireless sensor networks are powerful, distributed, self-organizing systems used for event and environmental monitoring. In-network query processors like TinyDB offer a user friendly SQL-like application development. Due to the sensor nodes?? resource limitations, monolithic approaches often support only a restricted number of operators. For this reason, complex processing is typically outsourced to the base station. Nevertheless, previous work has shown that complete or partial in-network processing can be more efficient than the base station approach. In this paper, we introduce AnduIN, a system for developing, deploying, and running complex in-network processing tasks. In particular, we present the query planning and execution strategies used in AnduIN, a system combining sensor-local in-network processing and a data stream engine. Query planning employs a multi-dimensional cost model taking energy consumption into account and decides autonomously which query parts will be processed within the sensor network and which parts will be processed at the central instance.     

Effects of road surface appearance and low friction warning systems on driver behaviour and confidence in the warning system

Warning systems for slippery road conditions are a potential newcomer among driver support systems. A total of 75 participants drove in a high-fidelity driving simulator on roads with both visible and invisible ice, to investigate to which extent drivers rely on a low friction warning system. Three experimental groups with different versions of a low friction warning system and a control group without warning system were compared. All drivers ranked the systems according to trust. A system displaying recommended speed received the best ratings. Driving speed was analysed for three particular segments of the route. Generally, lowest speeds were achieved with the recommended speed system. The participants drove more slowly on a slippery segment that looked icy than on the segments that looked dry when they did not receive a low friction warning. When they received a warning for low friction they also lowered their speed for the segment looking like asphalt. The results provide guidelines for how to present low friction warnings to drivers. The design has substantial effects on the resulting behaviour and therefore it can have a high impact on traffic safety. So far, not much research on low friction warning systems has been reported.