Meaning
Non-destructive internal imaging of wound or stacked pouch cells determines the physical margins between electrode boundaries. This spatial clearance, known as CT scan overhang, measures the distance by which the anode extends past the cathode to ensure complete coverage. It serves to verify that no lithium plating will occur at the cathode edges during charging.
Safety Margin
Insufficient overlap of the anode allows lithium ions to accumulate at the cathode perimeter without a corresponding intercalation site. Analyzing the CT scan overhang helps manufacturers identify regions of localized lithium plating. This prevents the formation of hazardous metallic dendrites that can cause internal short circuits.
Measurement Protocol
Advanced computer tomography systems capture high-resolution cross-sectional slices of the cell under test. Determining the CT scan overhang requires measuring the difference in electrode lengths from these reconstructed three-dimensional images at multiple points along the bend or stack. This non-destructive inspection is performed on random production samples to monitor alignment accuracy and detects internal mechanical defects that cannot be seen by outward visual checks.
Process Control
Electrode winding and stacking machines must be calibrated to maintain tight tolerances. Fluctuations in mechanical tension can degrade the CT scan overhang during assembly. Maintaining a proper clearance minimizes the risk of producing batteries that fail early in their lifecycle.
