Merits of the Cell Bottom Vent Feature in 18650 Cells for Preventing Side Wall Rupture - (PPT)

摘要

Side wall ruptures (SWR) during TR can defeat all other measures to prevent propagation in batteries. Factors that drive up the risk of SWR: - High energy density (> 660 Wh/L or > 2.8Ah in 18650) based on past, present experience; - High rate kinetics of chemical decomposition; - High pressure of cell enclosure relief features: (1) Battery restraining features impact on cell pressure relief are important; - Type and location of internal short: (1) External heater on can wall, oven, or internal short circuit device. Merits of bottom vents, thicker can walls: - Both lowers SWR risk very significantly; - ISC device shows that risk is not eliminated solely with either feature; Merits of bottom vents vs thicker can walls: - Less violent TR (higher post test mass) with bottom vents. ISC device generates intense localized thermal event not replicated by external heating (either evenly with oven or concentrated with heater).