Analysis of the Interaction and Variability of Thermal Decomposition Reactions of a Li-ion Battery Cell

Lithium-ion battery cells with high energy density are widely used in today's electric vehicles. However, thermal runaway (TR) of a battery cell is still a major safety issue in the use of lithium-ion batteries in the automotive sector. In particular, the variability of TR, which is not yet fully understood, can lead to significant safety issues. This paper investigates the variability of individual decomposition reactions during TR and their influence on the overall scattering of TR behavior. Therefore, differential scanning calorimetry (DSC) measurements on individual cell components and their combinations are carried out through multiple repetitions. It is found that the individual heat release contributions of different chemical reactions show significant variations to the overall heat release of the TR. The heat release of anode/electrolyte reactions show a variability of up to 47 %, whereas the cathode/electrolyte reactions show more consistent heat release. The reactions are summarized in an energy release diagram to combine the varying behavior of individual reactions with the overall TR chain reaction mechanism. Thus, the scattering of TR behavior of a cell can be mapped based on the variability of individual reactions. These findings should help to understand the scattering of TR behavior already at the material level.

Automated summary

Lithium-ion battery cells with high energy density are widely used in electric vehicles, but thermal runaway remains a major safety issue. This study investigates the variability of individual decomposition reactions during thermal runaway and their influence on overall behavior. Through differential scanning calorimetry measurements, it is found that different chemical reactions show significant variations in heat release. Mapping the variability of individual reactions helps to understand the scattering of thermal runaway behavior at the material level.