Li-ion batteries have many postive atributes which explains their rapid integration into many portable and stationary applications. Still thermal runaway of these cells remain a major issue which requires engineering controls and testing. Runaways can occur due to internal or external shorting of a cell/pack or from the mechanical impact due to crushing or penetration. Understanding how these thermal runaway events occur and the resultant temperature and pressure changes within the cell is critical in designing safety systems to reduce the likelihood and/or mitigate the consequence of such thermal failures. Adiabatic calorimetry has been applied to studying the thermal decomposition of cells as it provides a "worst case" or adiabatic scenario in measuring thermal runaway within a cell. All the heat released from an exothermic reaction within the cell (i.e., decomposition, discharge) is maintained within the cells causing the cell temperature to increase. This leads to faster reactions, more heat production, higher temperatures, and eventually to thermal runway and catastrophic cell failure. Adiabatic calorimeters, more so then most other types of laboratory calorimeters, are designed to withstand repeated thermal runaway and potential explosions. It is now possible to measure inside a closed, high tracking rate adiabatic calorimeter, the temperature and pressure rise from nail penetration of an 18650 cell before, during, and after a nail penetration test. This information is critical in understanding how to prevent cascading cell failure in a battery pack from one runaway cell.
展开▼
