Analysis of solid combustion products to establish a theoretical model of the causes of thermal runaway of ternary lithium-ion battery overcharge and heating

It is difficult to determine whether ternary lithium-ion batteries (t-LIBs) were the “source” of the actual fire scene because of the little available direct evidence left after thermal runaway combustion of lithium-ion batteries (LIBs) and the lack of relevant analytical methods for t-LIBs after complete combustion. As a result, a large number of fires involving t-LIBs are controversially identified as the cause every year. In this paper, we conducted experiments on the two most common thermal runaway types of t-LIBs to investigate the correlation model between their combustion products and thermal runaway types. In the case of overcharge, the combustion products (black powder) of t-LIBs contain aluminum elements, which may be due to the thermal reaction of aluminum. In contrast, in the case of heating, the combustion products of t-LIBs have almost no detectable elemental aluminum. The reason may be due to the ability of the electrode material to continuously decompose and precipitate a large amount of metal oxides under the overcharge condition, which constitutes the condition for the occurrence of the aluminum thermal reaction, making the presence of Al2O3 in the combustion products. However, the lack of continuous current action under the heating condition prevents the generation of the aluminum thermal reaction.