The safety of lithium ion batteries in vehicles is a priority of the automotive industry. The focus of the development activities are the reduction of the risks and the improvement of the safety concepts and systems.

In the last few years some incidents and accidents have taken place;​ a short overview about the state of the art of lithium ion battery technology on cell and battery level with focus on safety features, the risks, the statistical relevance and occurred incidents or accidents will be given.

An overview about dangerous events (worldwide) with lithium ion batteries for vehicles will be given (for cars as well as for test facilities);​ this overview is limited to data that is publicly available. A statistical significance based on this data will be shown;​ it includes the total number of vehicles in the relevant markets and an outlook for the future. In conclusion, the absolute number of safety relevant events is low because of the low number of electric and hybrid vehicles on the market. The absolute risk is low as well. The risk of safetyrelated incidents per electric or hybrid vehicle is much higher. Ultimately it depends on the used trigger;​ if vehicle accidents are seen as the trigger for battery incidents, the risk is low.

Using a bottom-up safety assessment approach in which the estimated risks for the cell, module, and battery are described, and the hazard levels and risk levels for their use in vehicles are determined will give an excellent overview. A description of additional and possibly future relevant safety features like changes in cell chemistry (additives, improved separators or flame retardant electrolytes) will be included. Furthermore, an assessment of these additional relevant safety features will be given. This main finding of this assessment is that the safety level of a lithium ion battery depends mainly on the cell chemistry and its capacity. The use of additives can improve the safety, but will lead to lower capacity and performance and result in higher prices. Other additional features won’t have any impact regarding battery safety.

From this it is possible to define requirements for the safety of vehicles regarding:​ package, crash behaviour, and functional safety. The current safety level of electric and hybrid vehicles (concepts and characteristics) will be shown and discussed.

Finally information about new technology and trends for lithium batteries will be given, including information about relevant safety characteristics. This study is limited to lithium ion batteries used in electric and hybrid vehicles.