Electric vehicle (EV) batteries, i.e., currently almost exclusively lithium-ion batteries, are removed from the vehicle once they no longer meet certain requirements. However, instead of being disposed of or recycled, the removed batteries can be used in another, less demanding application, giving them a “second life”. Research in the field of second-life batteries (SLBs) is still at an early stage and, to better understand the “second life” concept and the related challenges, potential second-life applications need to be identified first. Using a detailed study of the scientific literature and an interview with field experts, a list of potential second-life applications was drafted. Afterwards, a technical, economic, and legal evaluation was conducted to identify the most promising options. The findings of this research consisted of the identification of 65 different mobile, semi-stationary and stationary second-life applications; the applications selected as most promising are automated guided vehicles (AGVs) and industrial energy storage systems (ESSs) with renewable firming purposes. This research confirms the great potential of SLBs indicating that second-life applications are many and belong to a broad spectrum of different sectors. The applications identified as most promising are particularly attractive for the second-life use of batteries as they belong to fast-growing markets.

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.

Information derived from microscopic images of Li-ion cells is the base for research on the function, the safety, and the degradation of Li-ion batteries. This research was carried out to acquire information required to understand the mechanical properties of Li-ion cells. Parameters such as layer thicknesses, material compositions, and surface properties play important roles in the analysis and the further development of Li-ion batteries. In this work, relevant parameters were derived using microscopic imaging and analysis techniques. The quality and the usability of the measured data, however, are tightly connected to the sample generation, the preparation methods used, and the measurement device selected. Differences in specimen post-processing methods and measurement setups contribute to variability in the measured results. In this paper, the complete sample preparation procedure and analytical methodology are described, variations in the measured dataset are highlighted, and the study findings are discussed in detail. The presented results were obtained from an analysis conducted on a state-of-the-art Li-ion pouch cell applied in an electric vehicle that is currently commercially available.