Proceedings of the Ninth International Seminar on Fire and Explosion Hazards (ISFEH9), pp. 870-880 Edited by Snegirev A., Liu N.A., Tamanini F., Bradley D., Molkov V., and Chaumeix N. Published by Saint-Petersburg Polytechnic University Press ISBN: 978-5-7422-6498-9 DOI: 10.18720/spbpu/2/k19-49 870 Measuring the Energetics of a Lithium Ion Battery in Thermal Runaway Quintiere J.G. University of Maryland, Department of Fire Protection Engineering, College Park, MD, USA jimq@umd.edu ABSTRACT A calorimetry technique is developed to measure the energetics of an 18650 Li-ion battery in thermal runaway. The technique uses the battery as a calorimeter with temperature and mass loss measurements to analyze the energetics. Runaway is induced by heating of the battery. Only one battery is investigated over a range of heating power and state of charge (SOC). The dynamics of the battery are investigated including time events, temperature, mass lost and energies. The total energy in runaway is manifested by the internal energy stored in the battery and the enthalpy of the ejected mass. Combustion of the ejected gases is not studied here. Here a safety vent first causes the release of gases, then this is followed by the more dominant ejection during runaway. Vent times decrease dramatically with heating power. The duration of runaway decreases with the SOC, and runaway energy increases with the SOC. The total energy measured in runaway is compared to an alternative technical to show its accuracy. The need to assume a specific heat of the ejected mass in the current technique has an effect on accuracy. Also the possibility of melting in runaway is not included in the current technique. KEYWORDS: Batteries, calorimeter, Li-ion, thermal runaway. INTRODUCTION Lithium ion batteries have a high electrical energy density. These batteries are used extensively in commercial products from electronics to powering automobiles. As with any new technology they can cause unanticipated safety issues. It has become well known that such batteries are prone to “thermal runaway” that can lead to fire and explosion hazards [1-3]. In general, thermal runaway is a process that is accelerated due to temperature. It involves a feedback mechanism in which the exothermic energy produces an increase in temperature, and the temperature causes an increase in the rate of energy generated. In runaway of a Li-ion battery, many exothermic decomposition reactions are triggered among its components, and modeling all of the electrical and chemical processes in runaway is very complex [4-6]. The primary hazard from the runaway of a battery is the transfer of this energy to other batteries causing a possible chain reaction, and the transfer of energy to the surrounding materials to cause fire and possible explosion in a confined system. The energy dynamics of runaway are key in the design of safety mitigation systems to prevent the consequences from runaway. A typical Li-ion battery consists of a cathode of a lithium metal oxide on aluminum and a graphite anode on copper. The electrolyte is an organic solvent and is combustible. A plastic membrane separator, within the electrolyte, limits the ion transfer between the anode and cathode. The separator is a key failure point in the initiation of runaway. Failure can be initiated in several ways: (1) a manufacturing defect that produces dendritic growth breaking the membrane, (2) heating to cause the membrane to melt, (3) direct accidental puncture, and (4) over-charging. Failure of the membrane leads to an internal short circuit and thermal runaway.