Experimental investigation on thermal runaway suspension with battery health retention

Abstract

With growing applications of Li-ion batteries in ground transportation and energy storage, thermal runaway of Li-ion batteries has become a major concern for energy and public safety. Existing studies on thermal runaway mitigation methods are largely passive, in that most of them focus on propagation mitigation and fire extinguish after thermal runaway has been triggered. In this work, we presented experimental results on thermal runaway suspension with battery health retention, for the first time. By analyzing the temperature and voltage evolution of commercial 18,650 cells with Lithium iron phosphate chemistry during step-heating thermal runaway test in an accelerating rate calorimeter, it is found that the voltage signal has a sudden drop corresponding to a similar temperature of 135 °C, before the occurrence of thermal runaway. Thermal runaway suspension experiments are then conducted by activating cooling when either the voltage drop or the target temperature signal is reached. It is observed that thermal runaway suspension from the target voltage drop signal fails to prevent the battery from further damage, even with fast liquid N2 cooling. For thermal runaway suspension at the temperature signal 130 °C, batteries are successfully saved regardless of fast cooling with liquid N2, or slow cooling using N2 gas. Further electrical impedance spectrum testing shows that the batteries survived 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.