Abstract
A multi scale multi domain (MSMD) model for large format lithium-ion battery (LIB) cells is presented. In our approach the homogenization is performed on two scales (i) from the particulate electrodes to homogenized electrode materials using an extended Newman model and (ii) from individual cell layer materials to a homogenized battery material with anisotropic electrical and thermal transport properties. Both intertwined homogenizations are necessary for considering electrochemical-thermal details related to microstructural and material features of electrode and electrolyte layers at affordable computational costs. Simulation results validate the MSMD model compared to the homogenized Newman model for isothermal cases. The strength of the MSMD model is demonstrated for non-isothermal conditions, namely for a 120 Ah cell discharged with four different cooling concepts: (i) without cooling (ii) with a base plate cooling (iii) with a tab cooling and (iv) with a side cooling. As one result, temperature gradients cause a local peak discharge up to 2.8 C for a global 2 C discharge rate.
Highlights
The increasing demand for electric mobility results in the growing relevance of large-format battery cells for electric vehicles
While comparable previous model studies [1,12,13,18,22] focus on thermal inhomogeneities, the last part of our study impressively demonstrates how inhomogeneous cell conditions and local discharge rates are interlinked
We introduce novel homogenization approaches on two scales: (1) from the particulate electrodes to homogenized electrode materials using an extended Newman model and (2) from different material layers in the cell to a homogenized battery material with anisotropic electrical and thermal transport properties
Summary
The increasing demand for electric mobility results in the growing relevance of large-format battery cells for electric vehicles In this case, electrode potentials and temperatures become heterogeneous at charging and discharging, as shown by Guo et al [1]. The lithium diffusion in the active material phase is considered by an additional model calculating solid state diffusion in spherical particles. The solution domains are (i) the cell level for physical processes in the 10 cm scale, (ii) the electrode level for electrochemical processes in the 100 μm scale and (iii) the (active material) particle level for the solid-state diffusion in the 1 μm scale. The model’s capability is demonstrated in the results section, where a comparison with the Newman model is made for isothermal und non-isothermal cases as well as a simulation study comparing four different cooling conditions: (i) without cooling (ii) with a base plate cooling (iii) with a tab cooling and (iv) with a side cooling
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