Characteristics of thermal runaway and propagation for 18650 lithium batteries in top-confined space

Abstract

Lithium-ion batteries (LIBs) are usually used in a narrow space, which can cause serious fire accidents if thermal runaway (TR) occurs. However, few studies have investigated the effect of top-confined space on LIB's jet fire as well as thermal runaway propagation (TRP). In this work, the top-confined space was constructed using top baffle, and a battery module for heat transfer analysis was constructed using aluminum columns with refractory ceramic fibre (RCF). Collected the data of the whole thermal runaway process of the battery module in the top-confined space. The behaviours of TR ceiling jet fire under different heights of baffle have been divided into three stages. Confirmed the effect of early-produced gas being ignited on TRP. Innovating a kind of calculate method of heat release ratio (HRR) under top-confined space. Calculated the amount of battery being heated during ceiling jet fire process. Summarised the effect of baffle height on thermal runaway propagation. The results show that 3cm or less between the baffle and batteries can lead to a violent combustion stage which does not present at other heights of baffle. The HRR of this stage is at least 5 times higher than the stable combustion stage. When the distance between the baffle and batteries is increased from 1 to 3cm, the percentage of heat transfer from the ceiling jet fire decreases from 60.3 % to 24.3 %, and the percentage of heat transfer between batteries increased from 14.2 % to 61.6 %. When the distance between the baffle and batteries is 2cm or less, TRP time is at least 1.7 times higher than other heights of baffle, as well as reduce the intensity level of TR for the propagated battery.