Raphael Zahn

Last Name

Zahn

First Name

Raphael

ORCID

0000-0003-0223-0697

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Publications 1 - 10 of 27

A physical model describing the interaction of nuclear transport receptors with FG nucleoporin domain assemblies
Zahn, Raphael; Osmanović, Dino; Ehret, Severin; et al. (2016)
eLife
The permeability barrier of nuclear pore complexes (NPCs) controls bulk nucleocytoplasmic exchange. It consists of nucleoporin domains rich in phenylalanine-glycine motifs (FG domains). As a bottom-up nanoscale model for the permeability barrier, we have used planar films produced with three different end-grafted FG domains, and quantitatively analyzed the binding of two different nuclear transport receptors (NTRs), NTF2 and Importin b, together with the concomitant film thickness changes. NTR binding caused only moderate changes in film thickness; the binding isotherms showed negative cooperativity and could all be mapped onto a single master curve. This universal NTR binding behavior – a key element for the transport selectivity of the NPC – was quantitatively reproduced by a physical model that treats FG domains as regular, flexible polymers, and NTRs as spherical colloids with a homogeneous surface, ignoring the detailed arrangement of interaction sites along FG domains and on the NTR surface.
Designing Polyolefin Separators to Minimize the Impact of Local Compressive Stresses on Lithium Ion Battery Performance
Lagadec, Marie-Francine; Zahn, Raphael; Wood, Vanessa (2018)
Journal of the Electrochemical Society
Swelling of electrochemically active polyelectrolyte multilayers
Zahn, Raphael; Vörös, Janos; Zambelli, Tomaso (2010)
Current Opinion in Colloid & Interface Science
3D Electrochemical-Mechanical Battery Simulation Tool: Implementation with Full Cell Simulations and Verification with Operando X-ray Tomography
Wenzler, Nils; Rief, Sebastian; Linden, Sven; et al. (2023)
Journal of the Electrochemical Society
Most commercially used electrode materials contract and expand upon cycling. This change in volume influences the microstructure of the cell stack, which in turn impacts a range of performance parameters. Since direct observation of these microstructural changes with operando experiments is challenging and time intensive, a simulation tool that takes a real or artificially generated 3D microstructure and captures the volumetric changes in a cell during cycling would be valuable to enable rapid understanding of the impact of material choice, electrode and cell design, and operating conditions on the microstructural changes and identification of sources of mechanically-driven cell aging. Here, we report the development and verification of such a 3D electrochemical-mechanical tool, and provide an example use-case. We validate the tool by simulating the microstructural evolution of a graphite anode and a Li(Ni,Mn,Co)O2 cathode during cycling and comparing the results to X-ray tomography datasets of these electrodes taken during cycling. As an example use case for such a simulation tool, we explore how different volumetric expansion behaviors of the cathode material impact strain in the cell stack, illustrating how the material selection and its operation impact the mechanical behavior inside a cell.
Effect of polyelectrolyte interdiffusion on electron transport in redox-active polyelectrolyte multilayers
Zahn, Raphael; Coullerez, Géraldine; Vörös, Janos; et al. (2012)
Journal of Materials Chemistry
Effect of Positional Disorders on Charge Transport in Nanocrystal Quantum Dot Thin Films
Xing, Yunhua; Yazdani, Nuri; Lin, Weyde M.M.; et al. (2022)
ACS Applied Electronic Materials
Understanding the impact of positional and energetic disorders in nanocrystal (NC) quantum dot thin films on charge transport is crucial to determine what to prioritize in terms of the synthesis and fabrication of these materials and to accelerate their development for electronics. Here, we computationally construct realistic NC thin films with different types of disorders and apply a density functional theory (DFT)-parameterized, kinetic Monte Carlo simulation to systematically study the effects of disorders on transport. We obtain statistics on the carrier transit pathways through the NC films and carrier residence times on individual NCs. This provides insights into the distribution of transit times across the thin films and the effective mobility. We conclude that the impact of positional disorders on charge transport depends on the type of disorder and how it affects the spacing between neighboring NCs. The formation of transport paths with short inter-NC distances can enhance mobility. Meanwhile, random packing (RP) of NCs and energetic disorders due to a distribution of NC sizes decreases mobility 2- to 4-fold. Because of the large reorganization energy of small NCs, increasing the electric field has little influence on the median residence time of a charge carrier on an NC; however, an electric field straightens the transport path of the charge carrier and reduces the average number of hops a carrier makes, which can slightly enhance mobility. Deep electronic trap states are especially detrimental to carrier mobility, particularly at low fields and when the films are otherwise highly ordered.
Topological and network analysis of lithium ion battery components: the importance of pore space connectivity for cell operation
Lagadec, Marie-Francine; Zahn, Raphael; Müller, Simon; et al. (2018)
Energy & Environmental Science
The structure of lithium ion battery components, such as electrodes and separators, are commonly characterised in terms of their porosity and tortuosity. The ratio of these values gives the effective transport coefficient of lithium ions in the electrolyte-filled pore spaces, which can be used to determine the ionic resistivity and corresponding voltage losses. Here, we show that these microstructural characteristics are not sufficient. Analysis of tomographic data of commercial separators reveals that different polyolefin separators have similar porosity and through-plane tortuosity, which, in the homogenised picture of lithium ion cell operation, would imply that these different separators exhibit similar performance. However, numerical diffusion simulations indicate that this is not the case. We demonstrate that the extent to which lithium ion concentration gradients are induced or smoothed by the separator structure is linked to pore space connectivity, a parameter that can be determined by topological or network based analysis of separators. These findings enable us to propose how to design separator microstructures that are safer and accommodate fast charge and discharge.
Communication ‒ Technique for Visualization and Quantification of Lithium-Ion Battery Separator Microstructure
Lagadec, Marie-Francine; Ebner, Martin; Zahn, Raphael; et al. (2016)
Journal of the Electrochemical Society
Separators play an important role in lithium-ion battery operation; however, no comprehensive studies of their microstructure and its impact exist. To enable such studies, we present a simple method for separator microstructure visualization and quantification based on focused-ion-beam scanning electron microscopic tomography. Here, we use this approach to visualize a sample of commercial polyethylene separator, calculate its directional effective transport parameters, and explain the impact of these values on battery performance. We further extend this technique to visualize metallic deposition within the separator, which could facilitate the study of lithium plating and dendritic growth.
Polyelectrolyte-modified Separators for High-Performance Lithium Ion Batteries
Zahn, Raphael; Hess, Michael; Lagadec, Marie F.; et al. (2016)
Characterization and performance evaluation of lithium-ion battery separators
Lagadec, Marie-Francine; Zahn, Raphael; Wood, Vanessa (2019)
Nature Energy
Lithium-ion batteries (LIBs) with liquid electrolytes and microporous polyolefin separator membranes are ubiquitous. Though not necessarily an active component in a cell, the separator plays a key role in ion transport and influences rate performance, cell life and safety. As our understanding of separator properties and the interactions between the separator and the electrolyte deepens, it becomes evident that there are opportunities for improving separators to help meet the greater demands that new applications place on LIB technology. Here, we review the impact of the separator structure and chemistry on LIB performance, assess characterization techniques relevant for understanding structure–performance relationships in separator membranes, and provide an outlook on next-generation separator technology. Insights from this Review indicate that LIB performance can be improved by taking into account the interplay of the separator with its surroundings and indicate that, in the future, separators will be designed to play a more active role in LIB operation. Current and emerging characterization techniques will play an important role in guiding this evolution in separator technology.

Publications 1 - 10 of 27

Raphael Zahn

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