Detection of Critical Conditions in Pouch Cells Based on Their Expansion Behavior

Abstract

The present work examines 75 Ah nickel–cobalt–manganese (NMC)/graphite-based pouch cells with respect to their expansion behavior. The focus is on cell expansion due to critical cells according to the installation conditions of a battery module. Strain gauges were used for monitoring. By comparing the cell expansion in standard conditioning to that in an abuse (overcharging), information can be acquired about the suitability of the expansion behavior for early detection of critical cell states and to avoid resulting damage, e.g., cell opening or cell fire. The sequence of critical cell events has been shown to be easily reproducible; especially the first significant cell expansion due to internal gas formation, which was a reliable detection criterion for critical cell states.

Keywords

• lithium ion cell
• expansion behavior
• critical cell state
• thermal runaway
• cell monitoring