Ionization Based Sensor for Early Detection of Thermal Runaway Events in Lithium-Ion Batteries

Lithium-ion and lithium-metal battery cells are susceptible to a phenomenon known as thermal runaway under failure conditions. Thermal runaway entails a rapid escalation in battery cell temperature accompanied by the emission of flammable lithium ions, particulates, electrons, hydrocarbon, and hydrogen gases. These gases pose a significant ignition risk, potentially leading to fires and endangering occupants and bystanders. Therefore, the timely detection of thermal runaway is paramount for ensuring safety in proximity to such battery systems. Traditionally, thermal runaway sensors comprise intricate assemblies of pressure, temperature, and gas sensors, strategically positioned at the pressure relief valve of battery modules. Calibration of all sensors is essential to reliably detect thermal runaway conditions. An alternative method for thermal runaway detection involves the identification of ions and free electrons present in the gases emitted by the battery, utilizing Thermal and Chemi-ionization techniques. Another method entails ionizing the gases released from the battery prior the thermal runaway. Experimental investigations have been conducted, involving the placement of a fully charged battery pouch cell on a heater equipped with thermocouples and an ionization sensor, enclosed within a container with a controlled opening to the atmosphere. The heater's temperature was gradually increased to induce a thermal runaway reaction. Due to the absence of a vent valve, the pouch inflated with gas, causing it to rupture the pouch and fill the container. Subsequent analysis revealed a pronounced spike in the thermal runaway sensor signal prior to the thermal runaway event.