Image Based Modelling of Li-ion Battery Electrodes

Overview

The heterogeneous microstructure of lithium ion batteries (LIBs) remarkably influences performance by providing certain interfacial surface area, diffusion path, and active material connectivity. In this work, the LiFePO4 electrode microstructure of a LIB is reconstructed based on the nano-CT images in Simpleware software. The 3D model was then meshed and exported to COMSOL Multiphysics® for Finite Element Analysis (FEA). The results show that the electrode heterogeneity causes a wider range of physical and electrochemical properties compared to common homogenous models.

Key Characteristics:

  • Image data acquired from nano-CT
  • Segmentation in Simpleware ScanIP
  • Mesh generated in the Simpleware FE Module
  • Governing PDEs solved in COMSOL Multiphysics®

Thanks to

Kashkooli et al., 2016. Multi-scale modeling of lithium-ion battery electrodes based on nano-scale X-ray computed tomographyJournal of Power Sources, 307, 496-509.

 

Acknowledgements

This study was financially supported by the University of Akron and the Natural Sciences and Engineering Research Council of Canada (NSERC) through grants to Z.C. and the University of Waterloo.

Thanks to

Image Processing

Using Simpleware ScanIP, the obtained 2D stack from nano-CT was segmented utilizing thresholding technique to convert the greyscale stack to a binary stack.

The process included segmenting the active material particles and pore-PVDF-carbon regions from the scan. If the weight percentage of the active material is high, the carbon material and polymer binder are randomly distributed in the electrode. To reconstruct the connected solid matrix, it was assumed that the carbon material is randomly distributed among the active material to provide electronic connectivity.

A morphological close filter was used in Simpleware ScanIP on the active material region to fuse the neighbouring active material together.

Meshing

A voxel-based mesh of the model was generated using the Simpleware FE Module and exported directly to COMSOL Multiphysics® for solving governing PDEs related to developed LIB multiscale model.

In microscale, the model is based on the real 3D microstructure data, taking advantage of the traditional homogenous 1D model in macroscale to characterize discharge/charge performance. This framework was used for the Multiscale-Multiphysics study of LIB.

Simulation & Results

It is shown that this model can predict the experimental performance of LiFePO4 cathode at different discharge rates more accurately than the conventional homogenous models.

The approach employed in this study provides valuable insight into the spatial distribution of lithium ion inside the real microstructure of LIB electrodes.