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

Abstract

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.