Browsing by Author "Baran, V"

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    Energy landscape for Li-ion diffusion in the garnet-type solid electrolyte Li6.5La3Zr1.5Nb0.5O12 (LLZO-Nb)
    (De Gruyter, 2022-05-24) Strangmüller, S; Avdeev, M; Baran, V; Walke, P; Kirchberger, A; Nilges, T; Senyshyn, A
    A comprehensive understanding of the nexus of diffusion mechanisms on the atomic scale as well as structural influences on the ionic motion in solid electrolytes is key for further development of high-performing all-solid-state batteries. Therefore, current research not only focuses on the search for innovative materials, but also on the study of diffusion pathways and ion dynamics in ionic conductors. In this context, we report on the extended characterization of the ionic electrolyte Li6.5La3Zr1.5Nb0.5O12 (LLZO-Nb). The commercially available material is analyzed by a combination of powder X-ray (either lab- or synchrotron-based) and neutron diffraction. Details of lithium disorder were obtained from high-resolution neutron diffraction data, from which the ionic transport of Li ions was determined by applying the maximum entropy method in combination with the one-particle potential formalism. © 2022 Walter de Gruyter GmbH
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    The structural behavior of electrochemically delithiated LixNi0.8Co0.15Al0.05O2 (x<1) battery cathodes
    (Elsevier, 2023-04-30) Hölderle, T; Monchak, M; Baran, V; Dolotko, O; Bette, S; Mikhailova, D; Voss, A; Avdeev, M; Ehrenberg, H; Müller-Buschbaum, P; Senyshyn, A
    A full series of variously delithiated LixNi0.8Co0.15Al0.05O2 (NCA) (x < 1) battery cathodes is extracted from cylinder Li-ion batteries of 18650-type, and structural studies of electrode materials are performed ex situ applying high-resolution neutron powder diffraction. A set of structural and microstructural parameters at different state-of-charges (SOC) is gathered from full-profile Rietveld refinements. Accurate cell metrics of the NCA lattice are obtained and compared for both, ex situ and operando modes of data collection. A detailed analysis of lithium occupancies and interatomic distances in the NCA cathode is carried out, revealing a shrinking material response of the NCA structure during delithiation, while the experimental quantification of Li/Ni cation mixing showed an SOC independent behavior. The observed deintercalation driven anisotropic broadening of the Bragg reflections in real-life NCA cathodes were analyzed and assigned to an increasing internal anisotropic microstrain, which is linked to the non-uniform distribution of Li in the structure of NCA, resulting in an unstable and unpredictable performance of LIBs. © 2023 Elsevier B.V.