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Günther, Jonas ; Stumböck, Nils ; Wycisk, Dominik ; Oldenburger, Marc ; Moos, Ralf ; Schmidt, Jan Philipp:
Determination of the Solid State Diffusion Coefficient Using Thin Model Electrodes : Transfer From NMC622 to NMC811.
2025
Veranstaltung: Oxford Battery Modelling Symposium (OBMS 2025)
, 24.7.-25.7.2025
, Oxford, United Kingdom.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Poster
)
Abstract
Physico-chemical battery cell models, such as the P2D model, are becoming increasingly important for the design and operation of lithium-ion batteries. A major challenge is the determination of the solid state diffusion coefficient (Ds) in the active material particles, since the typically studied porous electrodes are not purely limited by solid state diffusion. This poster summarizes recent progress in the determination of the solid state diffusion coefficient. It is based on thin electrodes (referred to as model electrodes) for parameterization, which improves the conventional Galvanostatic Intermittent Titration Technique (GITT), often applied to porous electrode systems. Furthermore, the optimized method is applied to model electrodes consisting of a single layer of spherical NMC811 particles and shows almost complete agreement with theoretical principles and reduced parasitic effects compared to the original NMC622 material. The improved GITT-Kang evaluation is applied together with impedance fitting and shows good agreement. Experimental cells constructed with a minimal lithium molality electrolyte allow precise determination of the dependence of the solid state diffusion coefficient on lithium stoichiometry and temperature. The results show good comparability with the observations made for NMC622, but differ by a generally increased diffusivity, a diffusivity drop at the Ni induced OCV plateau above 4.15 V at the H2 to H3 phase transition, and an increased state of charge dependence of the diffusion activation energy.