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