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An Investigation of Thermally-Induced Failure of Lithium Ion Batteries

Xuan Liu

Sponsor: 
Ford Motor

figure 1Lithium ion batteries (LIBs) are energy storage devices of growing importance because of high energy density, high efficiency and long life cycle.  As these devices are being deployed in a wider and wider range of energy demanding applications, their fire safety becomes an important consideration.  An LIB subjected to external heat (such as that from an adjacent fire) vents potentially combustible gases and aerosols and, subsequently, self-heats rapidly while simultaneously ejecting core electrode materials.  The former phenomenon is frequently referred to as safety venting; the latter is termed here as thermal runaway.  The visuals of these phenomena are shown on the right.

In the current study, thermal-induced failure of a particular form factor of LIBs, 18650, is being examined.  The purpose of the study is to develop a systematic procedure for the measurement of the rates and integral amounts of energy released during the two stages of battery failure.  These measurements are performed using a calorimeter designed in our laboratory, which schematic is shown on the right.  Battery failure is initiated by a small figure 2electric heater.  The internal energy release (due to thermal runaway) is determined from the temperature rise of the battery container and battery mass loss, which is monitored using a load cell (not shown on the schematic).  To simultaneously measure the heat produced in flaming combustion of vented products, the experiment is conducted inside a standard cone calorimeter, which gas analysis system is used to monitor oxygen consumed in the combustion process.  The amount of consumed oxygen is subsequently converted to heat release.

Examples of the internal energy release (P_reaction) histories obtained for batteries at different states of charge (SOC) are shown below.  These data are currently being utilized to construct a thermophysical model of the battery failure which purpose is to enable prediction of the battery behavior beyond the range of heating conditions realized in the current experiments.

Power Produced by Chemical Reactions Inside of 18650 LIB

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Xuan Liu

Xuan Liu is a Doctorate Student of the A. James Clark School of Engineering. For further information about his research, he can be contacted at:
LinkedIn: www.linkedin.com/in/xuanliufpe/

Student Phone: 
301-405-5300