Reliable and Early Warning of Lithium-Ion Battery Thermal Runaway Based on Electrochemical Impedance Spectrum

Lithium ion battery thermal runaway constitutes a severe inhibitor for the spread and application of electric vehicles and widespread adoption of renewable energy. Reliable and early warning of thermal runaway calls for a technique capable of detecting abnormal response well in advance of the critical event and being effective to the module when a single cell in it has safety issues. In this study, electrochemical impedance spectrum (EIS) dependence on cell temperature and deformation is exploited to generate a two-staged warning method with three indicators in three frequency ranges. Specifically, the first stage utilizes the high sensitivity of EIS at the intermediate-frequency range to abnormal cell internal temperature rise, which is before self-heating temperature, as an early indicator for safety issues. The second stage utilizes the abrupt changes in EIS behaviors due to cell deformation in high- and low-frequency ranges, which are more sensitive than cell voltage change, as indicators for the thermal runaway onset temperature. The potential and issues of such an EIS-based method for both reliable and early warning of thermal runaway in field application, including measurement feasibility, versatility in various scenarios and the difference between the experimental and actual situation, are discussed.