Due to the strong growth of lithium-ion-batteries in recent years, the focus is increasingly moving to the safe operation of batteries. A particular driver here is the social acceptance of electromobility, which is strongly influenced by the safety of traction batteries. Besides efforts on the material level, securing the cells by intelligent battery management systems and increasing or optimizing the cooling capacity implemented in the battery system to prevent propagation, the mitigation of thermal runaway is only implemented by the rupture valve.
The of the VentBatt project founded by the federal ministry of education and research is to investigate the outgassing products both in terms of chemical composition and physical properties, such as outflow volume flow and temperature. From the findings of these tests, on the one hand, the predictability of the thermal runaway is to be investigated on the basis of the state of charge and the temperature flank of the external heat supply. On the other hand, the possibility of early pressure release by means of an additional resealable valve will be examined in more detail.
Due to the complexity and the difficult chemical as well as thermodynamic test environment during the thermal runaway, the analysis of the escaping gases is critical. In addition, early relief of the cell by adding a second resealable valve as a hazard mitigation approach is an approach not yet investigated.
Besides the expected delay of thermal runaway, minimization of effluent gases and cooling of the cell are expected to increase the safety of lithium-ion batteries, especially with respect to propagation. In addition to the reduction of the cell temperature, an increase of the internal resistance of the cell can be expected, which, depending on the failure case, can minimize the heating up of the cell.