Numerical Study of Self-Heating Ignition of a Box of Lithium-Ion Batteries During Storage

Abstract

Many thermal events have been reported during storage and transport of large numbers of Lithium-ion batteries (LIBs), raising industry concerns and research interests in its mechanisms. Apart from electrochemical failure, self-heating ignition, driven by poor heat transfer could also be a possible cause of fire in large-scale ensembles of LIBs. The classical theories and models of self-heating ignition assume a homogeneous lumped system, whereas LIBs storage involves complex geometry and heterogeneous material composition due to the packaging and insulation, which significantly changes the heat transfer within the system. These effects on the self-heating behaviour of LIBs have not been studied yet. In this study, the self-heating ignition behaviour of a box containing 100 LiCoO2 (LCO) type of cylindrical cells with different insulation is numerically modelled using COMSOL Multiphysics with a multi-step reaction scheme. The model predicts that the critical ambient temperature triggering self-ignition of the box is 125°C, which is 30°C lower than that for a single cell, and the time to thermal runaway is predicted to be 15 times longer. The effects of different insulating materials and packing configurations are also analysed. This work provides novel insights into the self-heating of large-scale LIBs.

Experimental Study of Self-heating Ignition of Lithium-Ion Batteries During Storage: Effect of the Number of Cells

“…The upscaled results in Fig. 11 are only for the cells, not including the effects of packaging and boxes for storage, in which LIBs will be further insulated using separations and cushions, which could decrease the critical temperature of selfheating ignition [28]. This study presents: (i) an experimental proof that LIB self-heating during storage is possible and likelihood increases with the size of the ensemble, (ii) a method to upscale laboratory experiments to study self-heating of any battery types, and (iii) evidence that the cell used in this work at 30% SOC will not self-heat to ignition even at large scales when it is free from manufacturing flaws.…”

“…However, as only one cell was used in previous experiments [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], the number of cells and the consequent effects of heat transfer were neglected. The ignition of a LIB box has been numerically investigated by Hu et al [28]. Results show that insulating materials could decrease the critical temperature of self-heating ignition, because these materials reduce the heat dissipation of cells.…”

Anisotropic and homogeneous model of heat transfer for self-heating ignition of large ensembles of lithium-ion batteries during storage

“…We put forward a method to decouple the complex chemical reactions and heat transfer, using anisotropic homogeneous (Ani-Hom) heat transfer properties to simplify the Iso-Het heat transfer with the LIB storage system. The box with 100 cylindrical cells [37], as shown in Fig. 4 (a), is used as a case study to explain the methodology.…”

“…The problem is that the complex placement and structure during LIB storage (small gaps of This is the accepted version of this paper. Paper can be referenced as: insulation to separate cells to provide cushion and avoid short-circuits) have been proved to significantly change the internal heat transfer on the LIB storage system [37], and therefore should not be neglected for self-heating studies of LIBs. Directly simulating these narrow structures with a heterogeneous model would introduce more refined meshes (millimetre scale) and is numerically affordable for large-scale (warehouse scale) predictions.…”

Special Issue on Lithium Battery Fire Safety

“…Kong et al [10] describes the use of non-destructive computed tomography (CT) to analyse cylindrical Liion battery samples that underwent thermal runaway and exploded. Hu [11] and He [12] numerically and experimentally studied the self-heating ignition behaviour of a box of cells during storage, respectively. The full-scale thermal runaway test was conducted on real lithium-ion battery pack by Li et al [13].…”