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

<div class="section abstract"><div class="htmlview paragraph">Lithium-ion and lithium-metal battery cells are susceptible to a phenomenon known as thermal runaway under failure conditions. Given their widespread use in applications such as electric vehicles, portable electronics, and energy storage systems, early detection of thermal runaway is crucial for ensuring the safety of these battery systems. Thermal runaway entails a rapid escalation in battery cell temperature accompanied by the emission of flammable lithium ions, particulates, electrons, hydrocarbons, 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 ionization techniques. This paper presents an experimental investigation for the early detection of thermal runaway using a novel ionization sensor. The setup involves the placement of a fully charged battery pouch cell on a heater equipped with thermocouples and cell voltage measurement. The cell is enclosed within a container with a controlled opening to the atmosphere. A detailed analysis of the ionization signal was compared with the thermocouple measurements and battery voltage. In addition, a comparison between sealed and vented pouch cell batteries was made, and the detection of thermal runaway was analyzed. The novel sensor reliably detects early signs of thermal runaway in lithium-ion batteries, often before or during pouch rupture, making it valuable for early warning systems. Its effectiveness across different scenarios highlights its potential for integration into battery management systems to significantly enhance safety protocols.</div></div>