Battery Health Retention from Thermal Runaway Suspension

Abstract

With growing applications of Li-ion batteries in ground transportation and energy storage systems, thermal runaway of Li-ion batteries has become a major concern for energy and public safety. In this work, we come up with a strategy to suspend thermal runaway and meanwhile retain the electrochemical performance of the battery. We first analyzed the temperature and voltage evolution of commercial LFP 18650 cells during thermal runaway test following the standard heat-wait-seek strategy in an accelerating rate calorimeter (ARC). It is found that the voltage signal has a sudden drop corresponding to a similar temperature of 135 ℃, before the occurrence of thermal runaway. Thermal runaway suspension experiment is conducted by activating cooling when desired voltage and/or temperature signal is reached. It is observed that thermal runaway suspension from the voltage signal fails to prevent the battery from further damage. For thermal runaway suspension at the temperature signal 130 ℃, batteries are successfully saved regardless of fast liquid N2 cooling, or slow cooling using N2 gas. Further EIS testing shows that the batteries retained from thermal runaway suspension have increased bulk resistance while polarization resistance remains unchanged. The cycling performance of the saved batteries has demonstrated identical voltage but reduced capacity by around 20%. This research can provide useful guidance on thermal runaway prevention and health retention of Li-ion batteries.