Within the scope of developing a multi-physical model describing battery behavior during and after the mechanical load (accelerations, intrusions) of a vehicle’s high voltage battery, an internal short circuit model is of deep interest for a virtual hazard assessment. The internal short resistance and the size of the affected area must be known as a minimum for determining the released heat and, in consequence, the temperatures. The internal short resistance of purpose-built dummy pouch cells, filled with electrolyte-like solvent without conductive salt, has thus been measured in a given short area under various compressive loads. The resistances for different short scenarios obtained are analyzed and described in a mathematical form. Short circuit experiments with dummy cells using an external power source have also been carried out. This set-up allows the measurement of the temperature evolution at a known current and a determination of the actual short resistance. The post-mortem analysis of the samples shows a correlation between the maximum temperatures, released short heat and the separator melt diameter.

Lithium-ion batteries (LIBs) are commonly used in today’s electric vehicles. Studying their behaviour under mechanical loading, including short circuits, is vital for vehicle safety. This paper covers three major topics, (1) a general literature review for the state-of-the-art of LIBs, (2) physical cell tests for model validation are performed, wherein the occurrence of short circuits is detected and (3) creating a finite element model (FEM) of an 18650 cylindrical LIB using the most recent testing and simulation techniques. A variety of short-circuit criteria based on stresses, strains and geometric parameters have been implemented in the simulation and compared to the test results. It will be demonstrated that a combination of two geometric criteria, in the radial and axial directions of the cell, is best suited for virtual short-circuit detection in the simulation. Finally, the short-circuit criteria are implemented in a post-processing tool that allows fast short-circuit analysis of cells of different loadings. In the future, this method of short-circuit detection will be used to analyse an assembly of several battery cells such as, for instance, an automotive or maritime battery pack. Furthermore, the developed method enables mechanical integration with respect to crash safety in vehicles.

The Horizon 2020 LC-BAT-10-2020 project LIBERTY (" Lightweight Battery System for Extended Range at Improved Safety") focusses on the areas of battery lifetime, increased range, safety and environmental sustainability. The project aims to develop a battery pack that will have the same useful lifetime as those of current combustion engines, i.e. up to 20 years or 300,000 km. At present, the lifetime of a battery is typically lower, with guarantees of up to 10 years or around 150,000 km. LIBERTY targets a range increase of up to 20% compared to the benchmark vehicle, thus allowing driving up to 500 km on a single charge. Then, an ultra-fast-charging below 18 minutes is targeted, less than half the time realized by contemporary technologies. Improved and standardized battery safety and environmental life-cycle sustainability performance will serve other important aspects addressed by this project. To reach these goals the project is currently researching and developing the LIBERTY innovations described in more detail in the following sections.