Lithium ion batteries (LIB) became one of the key technologies for energy storage. The most important application is energy supply for mobile devices as well as for the green mobility because of their high energy density and their advanced stage of development. Therefore, LIB’s are not simply rated by their performance parameters but also by issues of safety.
With respect to the interaction of electrical and chemical hazards as well as emergence of fire and explosions, the thermal runaway represents the main risk potential related to the extended use of LIB’s. During thermal runaway, exothermal chemical reactions trigger further exothermal reactions, leading to the release of flammable and toxic gases plus particles. For safety studies a thermal runaway can be provoked by direct heating, overcharging or short circuit events. Such events can be analyzed via temperature and voltage monitoring, as well as measurements (qualitative and quantitative) of gaseous products and post mortem studies.
This study presents results of nail penetration tests in a custom-made battery cell investigation chamber. This chamber allows the determination of parameters which influence the response of battery cells to internal short circuit tests. The response is analyzed via measurement of cell voltage, temperatures as well as camera recording. Infrared gas species are identified and analyzed in-line by Fourier transform infrared spectroscopy (FTIR). The cells investigated in this study are manufactured, formed and electrochemically characterized. Cells of different capacity and chemistry (NMC111, NMC 622, NCA) are tested using a conductive nail material to determine the minimum required capacity to trigger a thermal runaway while using constant cell parameters. This study points out the scaling possibility of nail penetration experiments in lab scale for testing with low capacity battery cells. This results enable to development of safer and more efficient batteries for various use cases.