Tesla 4680 Cathode Porosity

Indicative numbers for the Tesla 4680 cathode porosity, estimated based on 2D images of the Batch 1 and 2 cells originally analysed for The Limiting Factor by the Laboratory for Energy Storage and Conversion, UC San Diego. This image analysis and estimation was performed by Addionics based on the original Tesla 4680 cell benchmarking.

Analysis and estimation of the Cathode Porosity was performed by Hicham Machrouki and Shawn Xiang at Addionics.

Porosity is a key parameter for the battery electrode performance and mechanical properties such as adhesion and structural electrode integrity during charge/discharge cycling.

The estimation used the following two images.

Porosity calculated from 2D: We estimated the porosity from 2D scan, as we did not have the slide scan from different angles.

• Method 1–segmentation: Assuming only two phase, the black shown in the image is the pore and the grey shown in the image is the particle. In this way, the porosity can be obtained from the segmentations.
• Method 2 –particle analysis: I used our algorithm to identify each particle and circle the particle, then estimating the area of each particle. In this way, the porosity can be obtained from the following calculations:
  • Porosity = 1-A_particles/A_total

Batch 1

In order to avoid the impacts of the current collector in the middle, we cropped the sub samples from top and bottom.

	Method 1 – Segmentation	Method 2 – Particle Analysis
Top	0.45	0.53
Bottom	0.43	0.57

Batch 2

	Method 1 – Segmentation	Method 2 – Particle Analysis
Top	0.45	0.56
Bottom	0.35	0.63

References

1. Fiji – an image processing package — a “batteries-included” distribution of ImageJ, bundling many plugins which facilitate scientific image analysis.
2. UC San Diego analysis, The Limiting Factor
   • Laboratory for Energy Storage and Conversion, UC San Diego
   • Ying Shirley Meng, UC San Diego