Having consistent power storage in batteries is important to customers. Checking for variable density within a cell indicates irregularities in manufacturing that can lead to a problem.
A Swiss roll or jelly roll cell is made by rolling up a single sheet of separator, cathode, and anode. Confirming the integrity of the layers is critical to its performance.
With a layered cell, confirming the strict alignment of the separator, anode, and cathode becomes critical. Deflected anodes can potentially lead to internal short circuits.