New Initiation Methods for Thermal Propagation Tests of Traction Li-Storages

Li-Ion technology is nowadays state of the art in electrical traction batteries. It promises high energy density and reliability but in case of a cell failure leading to an internal short circuit, a considerable amount of heat will be released. There are cases where the heat generated by internal short circuits is sufficient to turn all of the chemical energy stored in a cell into heat. Such cases are called a thermal runaway. In addition, the heat released in the cell can be transferred to neighbouring cells and trigger a thermal runaway in them as well. In this case, one speaks of thermal propagation, which in the worst case can spread to all cells in the battery storage. For thermal propagation testing of battery storage systems, a ISO standard ISO 6469-1 AMDENDMENT 1 was developed and published in November 2022 which describes how propagation test is carried out. To initialize the first cell, we have developed an initiation cell based on an electrically initiated thermite reaction, which generates the same amount of heat over time as the target cell used in the battery storage system. Thermite reactions are typical representatives of binary particle systems, which consist of a metal-oxide and a metal. Besides the concentrations of metal and metal-oxide, the burning velocity and therefore, the time-dependent heat development can be controlled by many other parameters like particle size or porosity, heat and mass transfer and the reaction kinetics or the casing. In this work, we developed a thermite replacement cell till a final technical demonstration of the cell to imitate the thermal propagation of a Li-Ion battery.