3D Resolved Computational Modeling to Simulate the Electrolyte Wetting of a Lithium‐Ion Battery Cell with 18650 Format

The electrolyte wetting of a lithium ion battery cylindrical cell is explored in this study with a 3D resolved continuum model that considers the exact spiral geometry found in commercial 18650 cells. The jelly roll architecture and capillary pressure are shown to be key determinants of the wetting degree and electrolyte distribution within the cell.

Electrolyte wetting in a lithium-ion battery (LIB) cell is a time-intensive and quality-critical manufacturing step that determines the degree of homogeneity of lithium ion's transport within the electrode and separator pores, affecting the overall ionic conductivity and current density. If the electrolyte is inadequately distributed, it can compromise the cell performance. In this work, we introduce a novel engineering-oriented model to simulate electrolyte wetting in a LiNi_0.33Mn_0.33Co_0.33O₂–graphite 18650 cylindrical LIB cell. Governing equations are supported on a pressure-saturation formulation incorporating Darcy's law and phase-transport expressions, solved through the finite element method in COMSOL Multiphysics. The model is parameterized with experimental data extracted from literature, and free parameters are optimized via a sensitivity analysis to maximize wetting. Results indicate that saturation is predominantly controlled by the capillary pressure and the spatial electrolyte distribution across the different functional layers of the jelly roll (electrodes and separator). The obtained electrolyte saturation of 86% is consistent with saturation values reported in literature obtained with different methodologies. Our 3D-resolved modeling approach uniquely captures how 18650 cell spiral geometry and component properties influence electrolyte distribution and, to the best of our knowledge, it is the first capable to simulate wetting behavior in a full-scale cylindrical LIB cell.

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