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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

NON-INVASIVE MEASUREMENT OF INTERNAL TEMPERATURE IN Li-ION CELLS FOR NOMINAL AND THERMAL RUNAWAY CONDITIONS

Get access (open in a dialog) DOI: 10.1615/IHTC16.ecs.023597
pages 4367-4375

Abstract

Temperature rise in a Li-ion cell during electrochemical energy conversion and storage presents serious performance, reliability and safety problems, including catastrophic failure due to thermal runaway. Measurement of the internal, core temperature of the cell is critical for monitoring the thermal state of the cell, and determining the extent of thermal management needed. This paper summarizes recent research on addressing this key technological challenge. By solving the governing energy conservation equations using the method of undetermined parameters, it is shown that core temperature of a heat-generating cylinder can be determined through appropriate time and space integrals of the measured temperature distribution on the outer surface. After validating the analytical model on a thermal test cell with embedded thermocouple, experiments are conducted to measure internal temperature of a 26650 Li-ion cell under a variety of operating conditions. Strong dependence of the internal temperature on discharge rate is observed. This method is extended to thermal runaway conditions, wherein the heat generation rate itself increases rapidly with temperature. Stepwise computation of the temperature field using the analytical model shows that the internal temperature of the Li-ion cell can be hundreds of degrees Celsius greater than the surface temperature. This is an important, fundamental insight into thermal runaway, and indicates that the cell may be at much greater risk of failure than is indicated by the surface temperature measurement. These non-invasive internal temperature measurement techniques may find applications far beyond Li-ion cells, as there exist multiple other engineering systems with significant internal heat generation, such as nuclear fuel rods, where the internal temperature is important for optimizing performance and ensuring safety.