Chemical Analysis of the Cause of Thermal Runaway of Lithium-Ion Iron Phosphate Batteries

Due to the lack of effective methods to determine the cause of thermal runaway of lithium-ion batteries (LIBs), many fires are wrongly classified as LIBs fires. In this paper, we conducted different types of LIBs experiments to study the stage of thermal runaway and the distribution of combustion products. Through experiments analysis, we discovered for the first time the characteristic elements associated with the cause of thermal runaway of LIBs in the solid combustion products. Under overcharge conditions, the aluminum element was detected for the combustion products. The main reason is that a large amount of metal oxides precipitated from electrode materials react with aluminum foil at high temperatures to form alumina (Al 2 O 3 ). However, under heating conditions, the aluminum element was not detected because of the lack of sufficient conditions for thermite reactions. The conclusion was verified by multiple sets of repeated experiments.