The safety of lithium-ion batteries has to be guaranteed over the complete lifetime considering geometry changes caused by reversible and irreversible swellings and degradation mechanisms. An understanding of the pressure distribution and gradients is necessary to optimize battery modules and avoid local degradation bearing the risk of safety-relevant battery changes. In this study, the pressure distribution of two fresh lithium-ion pouch cells was measured with an initial preload force of 300 or 4000 $\mathrm{N}$. Four identical cells were electrochemically aged with a 300 or 4000 $\mathrm{N}$ preload force. The irreversible thickness change was measured during aging. After aging, the reversible swelling behavior was investigated to draw conclusions on how the pressure distribution affected the aging behavior. A novel test setup was developed to measure the local cell thickness without contact and with high precision. The results suggested that the applied preload force affected the pressure distribution and pressure gradients on the cell surface. The pressure gradients were found to affect the locality of the irreversible swelling. Positions suffering from large pressure variations and gradients increased strongly in thickness and were affected in terms of their reversible swelling behavior. In particular, the edges of the investigated cells showed a strong thickness increase caused by pressure peaks.

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.

A set of five fire tests involving battery electric vehicles and conventional cars was performed in a tunnel. This data article provides the dataset of some of the determined parameters: air temperature, air velocity and heat release rate. The air temperature was measured at several locations and at different heights, distributed in the cross section of the tunnel. The velocity of the incoming air was also measured. The third parameter, the heat release rate (HRR), was calculated based on the enthalpy flow before and after the fire location. This parameter is important for characterizing the size of a vehicle fire. The data provide a reference for the evaluation of BEV fires and could be taken as reference for further fire studies. They might be also of interest to research groups dealing with simulation applications, like three-dimensional CFD simulations.

The safety of lithium-ion batteries within electrified vehicles plays an important role. Hazards can arise from contaminated batteries resulting from non-obvious damages or insufficient production processes. A systematic examination requires experimental methods to provoke a defined contamination. Two prerequisites were required: First, the extent and type of contamination should be determinable to exclude randomness. Second, specimens should work properly before the contamination, enabling realistic behavior. In this study, two experimental methods were developed to allow for the first time a controlled and reproducible application of water or oxygen into 11 single-layer full cells (Li₄Ti₅O₁₂/LiCoO₂) used as specimens during electrical cycling. Electrochemical impedance spectroscopy was used to continuously monitor the specimens and to fit the parameters of an equivalent circuit model (ECM). For the first time, these parameters were used to calibrate a machine-learning algorithm which was able to predict the contamination state. A decision tree was calibrated with the ECM parameters of eight specimens (training data) and was validated by predicting the contamination state of the three remaining specimens (test data). The prediction quality proved the usability of classification algorithms to monitor for contaminations or non-obvious battery damage after manufacturing and during use. It can be an integral part of battery management systems that increases vehicle safety.

Tunnel portals and tunnel lay-bys are hazardous spots for road users. Different infrastructure safety measures are in use, but the protection level is not known. In this study the following safety measures for reducing the injury risk are investigated: angular positioned 4 m and 8 m concrete barrier, crash cushion Alpina F1-50 and Alpina crash cushion. A passenger car equipped with a data acquisition unit is accelerated to 100 km/h and impacts the safety measure. The assessment of the latter is based on the EN 1317 criteria, specifically the Acceleration Severity Index (ASI), Theoretical Head Impact Velocity (THIV). Further assessment criteria are related to intrusions into the passenger compartment and post-crash motion. The best result in terms of ASI and THIV was achieved by the 8 m (ASI: 1.6, THIV: 30 km/h) concrete barrier. The crash cushion Alpina showed good results for the ASI (1.8) but the THIV (57 km/h) was less satisfactory, while the angular positioned 4 m concrete barrier (ASI: 2.9, THIV: 53 km/h) and the crash cushion Alpina F1-50 (ASI: 3.3, THIV: 74 km/h) performed worst. Even though some of the measures showed good results, no protection measure tested currently complies with all the assessment criteria used.

The electrode tabs of pouch cells are rigidly joined to the bus bar in a battery module to achieve an electric connection. The effect of abusive mechanical loads arising from crash-related deformation or the possible movement of battery cells caused by operation-dependent thickness variations has so far never been investigated. Three quasi-static abuse tests for the anode and cathode electrode tabs were conducted with pouch cells at 100% SOC. Tensile tests on the anode, cathode and pouch foil were performed in order to explain differences between the anode and cathode in the abuse tests. The experiments revealed different failure mechanisms for the anode and cathode electrode tabs. The cathode failed at an average maximum load of 940.3 N through an external rupture of the electrode tab. The anode failed at an average maximum load of 868.9 N through a rupture of the single electrode sheets and the opening of the pouch foil. No thermal runaway occurred for either cathode or anode. The results of this study reveal a more critical failure behavior for the anode electrode tab, which can be addressed in the future by adding a predetermined breaking point and adapting the geometry of the anode electrode tab.