Case Study #1: Failure Analysis of Dropped Prismatic Cell

After a handheld device containing a Li-ion prismatic cell was dropped, the cell burst into flames.


Failed cell as received


CT analysis shows a line of melted Cu along the top of the outer wrap of anode foil adjacent to the cathode tab.



Conclusion: The impact from dropping the device pushed the cell winding up hard against the cathode tab bend. Only a single layer of separator and a thin layer of tape separated the anode foil and cathode tab at this location. The insulating layers split, causing an internal short that resulted in cell failure. A thicker plastic insulator should be included to prevent this from happening.


Location of cathode tab in an opened exemplar