Method for predicting the fire risk of lithium-ion cells based on thermal management

A study on the statistical and computational analysis of the health and heat-generating behavior of long-cycle NCA/graphite cylindrical lithium-ion cells for energy storage applications, co-directed by Dr. Yoon- Cheol Ha at the Next Generation Battery Research Center of Korea Electrotechnology Research Institute (KERI, President Sung-ho Myung) and Dr. Yong Min Lee at the Department of Energy Science and Engineering of Daegu Gyeongbuk Institute of Science and Technology (DGIST ) was published in the Energy Sources Log. Tai-Jong Jung, a Ph.D. candidate in the Department of Electro-Functional Materials Engineering of the University of Science and Technology (UST) and Hyobin Lee, Ph.D. candidate for the DGIST contributed as first authors of the article.

Lithium-ion batteries are used in various industrial sectors and devices representing the fourth industrial revolution, including smart phones, electric vehicles (EV), energy storage systems (ESS), etc. a global problem, and there have also been massive ESS-related fires, both of which have received a lot of attention recently. Likewise, there is an increasing risk of fire and explosion in connection with the increased use of lithium-ion cells and therefore experts are trying to develop technologies to prevent the accident caused by the failure of management. thermal lithium-ion batteries.

Thermal management of lithium-ion cells is considered a key method for their safe use, as rapid cell degradation takes place when the temperature is too high or too low. However, the current “thermal management system” is generally designed based on the initial properties of new batteries and does not reflect the degraded properties caused by long-term cycling.

The research team simultaneously analyzed the effect of long-term use on cycle life and heat-generating behaviors and developed a method to predict potential fire hazard. Through scientific approaches, the study found that even normal cells without manufacturing defects, impact or other abuse factors can cause an accident when used for a long time without systematic thermal management.

This study was conducted on cylindrical cells (2.85 Ah) which is one of the most commonly produced lithium secondary batteries. The research team analyzed approximately 1.7 million time series data obtained from more than 1,000 tests under various C-rate conditions. For the first time in the world, they provided a statistical analysis of the effect of the C-rate on the cycle life and heat generation of lithium-ion cells, as previous studies provided simply the change in charge and discharge capacities with cycling.

The research team went further by developing a Python program for data visualization and its statistical analysis, and analyzed the long-term performance of the batteries. They also laid the foundation for numerical simulation by linking up with commercial software. This statistical and computational analysis should go a long way in improving the safety of EVs and ESSs in which hundreds or thousands of cells are assembled in a closed environment for energy storage.

KERI’s Dr. Yoon-Cheol Ha said, “People can know from experience that a smart phone gets hotter when they use it longer. This study is particularly significant because we applied a scientific approach by performing statistical and computational analysis to identify the cause of more heat generation from these long-cycle lithium-ion cells.We will continue to carry out our research activities to develop technologies for the stable operation of various types of batteries , including large format pocket cells and prismatic cells.

The study was published in the May issue of Energy Sources Log.

Provided by the National Science and Technology Research Council