Battery safety tests are defined by several international standards in different ways and with heterogenous termination and failure criteria. In this work, lithium-ion cells were examined regarding their behavior in the event of overcharging and also in the event of an external short circuit with varied parameters specified by standards. The voltage, current, and temperature curves were evaluated. In addition, the changes in the cells were analyzed using electrochemical impedance spectroscopy (EIS). It is shown that the cells exhibit reproducible behavior in a clamped state. Further, it could be determined that the position of the cell opening during an overcharge has an influence on the further behavior of the cell. EIS data showed that the cells have a significantly higher internal resistance after an overcharge. The short-circuit tests at different ambient temperatures indicated that the internal resistance of the cell decreases with increasing temperature. However, no reproducible effects in impedance spectra were present after the short-circuit test. This work illustrates that the choice of test parameters and termination criteria undoubtedly influence the test results and thus may change the classification of cells as either safe or unsafe. Thus, cells may be classified as safe regarding a certain standard but unsafe regarding another.

Second‐life batteries play a crucial role in advancing the principles of the circular economy and promoting sustainability in the energy sector. This study explores the impact of prior degradation referring to the extent and nature of aging experienced during a battery's first‐life application on the performance and lifetime of second‐life Li‐ion batteries (LIBs). Factors such as environmental sustainability and cost‐effectiveness are key drivers for the utilization of second‐life LIBs, with advancements in battery management systems, diagnostics, and refurbishment techniques enabling stakeholders to make informed decisions. This study explores various dimensions of first‐life degradation, including cycling degradation, capacity fade, lifespan reduction, and electrolyte decomposition, emphasizing the importance of understanding these processes to assess their impact on second‐life battery performance, optimize repurposing strategies, and ensure operational safety. Despite the progress made, there is still a need for further research to fully understand the cause and effect of the aging on the use case for second‐life batteries. In the end, this understanding will maximize their potential for use in sustainable energy infrastructure.

Spark ignition by low-energetic electrical discharges in combustible fuel/air mixtures is a significant safety risk in various industries. In the present paper, OH-LIF measurements and numerical simulations of the ignition and early flame propagation of hydrogen/air, propane/air and ethene/air mixtures are reported. The experiments, carried out at four energy levels close to the respective minimum ignition energy (MIE), show that higher energy input leads to a wider flame radius, which is in agreement with one-dimensional numerical simulations. Further, the evaluation of the radial OH distribution reveals the highly stochastic nature of this process if the introduced energy is near the respective MIE. By utilizing the combined methodical approach of experiments and simulations, the key factors impairing the experimental repeatability are identified. The numerical results indicate at lower energies a longer time delay between source time and ignition, during which loss processes and perturbations may lead to extinction. One important influencing factor is the three-dimensional flow induced by the discharge, effectively increasing the experimental scatter. The presented work facilitates a detailed view on the complex physiochemical mechanisms dominating ignitions of explosive gas mixtures by low-energetic electrical discharges.

The ignition of combustible/air mixtures by electrical discharges includes several physical and chemical processes. In process safety often the total available electrical energy is taken as a risk measure. However, to get a more detailed insight in the ignition process, also energy losses to the surrounding have to be considered. Additionally, for specific discharges not only the dissipation leading to thermal heating is of importance. Especially in the case of non-equilibrium plasma, a specific fractional amount of the discharge energy is used for electron impact dissociation, excitation, and ionization reactions, producing active radicals and ions during the discharge phase. While the electrical energy can be measured easily, it is difficult to determine energy losses. In this paper three different electrical discharges are examined experimentally and numerically to yield a better understanding of the ignition by electrical discharges.