Nils Wenzler


Last Name

Wenzler

First Name

Nils

ORCID

0000-0002-5713-8620

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2017 - 201922020 - 20233
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Publications 1 - 5 of 5
  • 3D Electrochemical-Mechanical Battery Simulation Tool: Implementation with Full Cell Simulations and Verification with Operando X-ray Tomography
    Item type: Journal Article
    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.
  • Deep learning-based segmentation of lithium-ion battery microstructures enhanced by artificially generated electrodes
    Item type: Journal Article
    Müller, Simon; Sauter, Christina Julia; Shunmugasundaram, Ramesh; et al. (2021)
    Nature Communications
    Accurate 3D representations of lithium-ion battery electrodes, in which the active particles, binder and pore phases are distinguished and labeled, can assist in understanding and ultimately improving battery performance. Here, we demonstrate a methodology for using deep-learning tools to achieve reliable segmentations of volumetric images of electrodes on which standard segmentation approaches fail due to insufficient contrast. We implement the 3D U-Net architecture for segmentation, and, to overcome the limitations of training data obtained experimentally through imaging, we show how synthetic learning data, consisting of realistic artificial electrode structures and their tomographic reconstructions, can be generated and used to enhance network performance. We apply our method to segment x-ray tomographic microscopy images of graphite-silicon composite electrodes and show it is accurate across standard metrics. We then apply it to obtain a statistically meaningful analysis of the microstructural evolution of the carbon-black and binder domain during battery operation.
  • Low temperature hydrothermal synthesis of battery grade lithium iron phosphate
    Item type: Journal Article
    Benedek, Peter; Wenzler, Nils; Yarema, Maksym; et al. (2017)
    RSC Advances
    Lithium ion transport through the cathode material LiFePO4 (LFP) occurs predominately along one-dimensional channels in the [010] direction. This drives interest in hydrothermal syntheses, which enable control over particle size and aspect ratio. However, typical hydrothermal syntheses are performed at high pressures and are energy intensive compared to solid-state reactions, making them less practical for commercial use. Here, we show that the use of high precursor concentrations enables us to achieve highly crystalline material at record low-temperatures via a hydrothermal route. We produce LFP platelets with thin [010] dimensions and low antisite defect concentrations that exhibit specific discharge capacities of 150 mA h g−1, comparable to material produced with higher temperature syntheses. An energy consumption analysis indicates that the energy required for our synthesis is 30% less than for typical hydrothermal syntheses and is comparable to solid-state reactions used today, highlighting the potential for low temperature hydrothermal synthesis routes in commercial battery material production.
  • Surface phonons of lithium ion battery active materials
    Item type: Journal Article
    Benedek, Peter; Yazdani, Nuri; Chen, Hungru; et al. (2019)
    Sustainable Energy & Fuels
    Surfaces of active materials are understood to play an important role in the performance and lifetime of lithium-ion batteries, but they remain poorly characterized and therefore cannot yet be systematically designed. Here, we combine inelastic neutron scattering and ab initio simulations to demonstrate that the structure of the surface of active materials differs from the interior of the particle. We use LiFePO4 (LFP) as a model system, and we find that carbon coating influences the Li–O bonding on the (010) LFP surface relative to the bulk. Our results highlight how coatings can be used to systematically engineer the vibrations of atoms at the surface of battery active materials, and thereby impact lithium ion transport, charge transfer, and surface reactivity.
Publications 1 - 5 of 5