CT-Based Inspection of Cylindrical Battery Cells Using Tescan UniTOM XL

What Makes Internal Geometry Critical in 26650 Cells

In cylindrical cells, structural precision directly influences thermal behavior, charge transport, and long-term durability. Electrode tabs must be correctly placed to minimize resistance and avoid current hotspots. The anode overhang — an intentional extension beyond the cathode edge — must be within strict tolerances to avoid lithium plating or incomplete charge distribution.

Cap components such as the current interrupt device (CID) and positive temperature coefficient (PTC) are the last line of defense in runaway scenarios. If any of these features are poorly manufactured or misaligned, they can compromise the entire cell. However, once a battery is sealed, these details are hidden — unless inspected by a non-destructive method like micro-CT.

Full-Cell Micro-CT with Structural Segmentation

A commercial 26650 cylindrical lithium-ion cell was scanned at high spatial resolution using the Tescan UniTOM XL system. Initial 2D slices captured the cell cap and sidewall for external evaluation. Full 3D reconstructions were carried out, with segmentation of key internal structures — including the jellyroll electrodes, tab connections, casing, and safety components in the cap.

Anode overhang was measured directly from the image data, and tab geometry was evaluated for symmetry, alignment, and position within the jellyroll. Additional segmentations highlighted the CID and PTC elements for safety device analysis.

Detecting Cap Damage, Tab Misalignment, and Electrode Offset

The 3D reconstructions exposed several structural features of interest:

These findings support the use of micro-CT in both development and quality assurance — allowing battery makers to spot construction issues early, optimize design tolerances, and verify safety-critical geometry without destructive testing.