The Current Interrupt Device (CID) is installed in cells to ensure their safety. The CID disconnects the cell electrically when the pressure inside the cell increases above the design level. The pressure increase inside the cell is due to gas formation caused by decomposition reactions which in itself is due to abuse conditions such as over-charge, over-discharge or internal shorting of the cell.
In a cylindrical cell the CID is built into the top section of the cell and “pops” up under pressure, thus electrically disconnecting the top cover from the jelly roll.
The CID is designed to operate before the cell vents.
In simple terms the operation is in stages as shown schematically below:
However, we also need to think about:
- normal operation
- activation pressure – typically in the case of an NMC/NCA 18650 cell the activation pressure is ~10 bar.
- reset pressure
- failure modes
- arcing
- corrosion
- mitigation
- production
- quality control
- test procedures
CID Operation under HV
As the CID opens the circuit there is a possibility of creating an arc. The situation is very similar to the case of the arc generated when opening contactors under load.
References
- Haß, J.; Schieber, C.; Meilinger, F.; Kotak, Y.; Sevinc, S.; Lang, P.; Schweiger, H.-G. Investigation of the Effects Caused by Current Interruption Devices of Lithium Cells at High Overvoltages. Appl. Sci. 2024
- Generic Safety, Handling and Qualification Guidelines for Lithium-Ion (Li-Ion) Batteries, NASA Aerospace Flight Battery Program
See also: Thermal Runaway, Shutdown Separators, Key Safety Features of Lithium-Ion Cells, Rupture Disc Integration for Overpressure Mitigation, Quantitative Battery Venting: A Worked Example, CATL’s “Dual Vent” Prismatic Cell