The project partners of the Technical University of Munich (TUM-EES), the RWTH Aachen University (RWTH-ISEA), the Fraunhofer Institute for Silicon Technology (FhG ISIT) and the Centre for Solar Energy and Hydrogen Research (ZSW-ECA) are working together on the NUBase project. The majority of electrical and a large number of thermal faults in a lithium-ion battery-based energy storage system can be intercepted by a reasonably designed battery management system (BMS). However, there will always remain a certain number of cell-based failure modes that cannot be adequately addressed by a BMS. If a thermal runaway (TR) of a cell now occurs, considerable energies are released and a subsequent thermal propagation (TP) through the entire system is highly probable, unless countermeasures are taken. The aim of the project is therefore to improve the understanding of the processes leading to TR, of TR itself and of propagation, and thus to enable more accurate cell design and production. To this end, various methods will be applied in the course of the project. To achieve this goal, various sensors (e.g. ultrasound, glass fibres, reference electrodes) will be installed on and in the cell to enable early detection of safety-critical conditions and to subsequently initiate countermeasures. Furthermore, the outgassing during venting of a lithium-ion cell is being investigated with a new type of test bench in order to gain a better understanding of the safety-critical TR process. The project will also investigate the feasibility of suppressing propagation by developing propagation barriers based on biodegradable and non-toxic materials to completely suppress thermal propagation. Previous experiments on propagation between several lithium-ion cells show that usually the TR of one cell spreads uncontrollably over the neighbouring cells. Experiments at the ZSW have now shown that it is possible to design propagation protection barriers that can effectively prevent propagation. However, the barriers developed at ZSW so far are not yet ready for the market in all properties, so that further developments are necessary in order to produce applicable products from them. Furthermore, the barriers are to be further developed so that they can also prevent propagation between cells with capacities of up to 60 Ah (suitable for automotive applications). Through these goals of the project, the two critical processes TR and TP that still exist in practice will be investigated in detail and limited with new monitoring methods, and battery safety will be significantly improved through the application of barrier materials.