3D Heterogeneous Model for Electrodes in Lithium-Ion Batteries and Its Application to a Modified Continuum Model

Abstract

The microstructures of porous electrodes in lithium-ion cells strongly affect their electrochemical performance. Experimental tomography techniques to investigate the microstructure during electrode development is costly and time consuming. To address this issue, a numerical method is presented to create a digital morphology to realize a realistic microstructure. In this study, the spherical harmonics in a straightforward mathematical approach are proposed to develop the virtual 3D morphology of the electrode’s heterogeneous structure. The introduced method offers a numerically light procedure which enables effective iterative virtual testing and optimization. The generated morphology model is parameterized to reproduce a NMC cathode microstructure observed in the literature. The electrode model allows evaluation of the spatially resolved geometric, transport and electric potential characteristics of the microstructure. The computed characteristics are employed to improve the parametrization of the continuum model as the most widely used physics-based model. For this purpose, the electrochemical impedance spectra of a lithium foil/separator/NMC half-cell is virtually modeled by heterogeneous and continuum approaches. Then, the modified continuum model is compared to the heterogeneous model as a benchmark, in terms of the kinetics and transport characteristics underlying the electrochemical impedance spectra. The modified continuum model shows an improved response in both frequency and time domains.

Keywords

• lithium ion batteries
• electrode microstructure
• spherical harmonics
• electrochemical impedance spectroscopy
• heterogeneous physical model
• modified continuum model