TY - CONF A1 - Leonhardt, Robert T1 - Impedance-based characterization of the overstress-related degradationin alkali metal-ion cells N2 - The successful repurposing of degraded alkali metal-ion batteries in second-life applications is a vital step towards achieving a circular economy. While reusing aged cells is a promising way of mitigating their overall environmental footprint, it is crucial to anticipate their future safety and performance characteristics. Unfortunately, predicting these properties is a cumbersome task, essentially caused by limited knowledge of the interference of different degradation modes in the cells’ first life. To still enable estimating of these parameters from a current state, the present study systematically investigates the impact of abusive conditions in an early phase of the cells’ life on their subsequent degradation behavior. For this purpose, individual lithium-ion and sodium-ion cells are initially stressed by different measures such as deep-discharging, high-temperature conditions, and deliberate combinations of the aforementioned methods. Electrochemical performance indicators are monitored during subsequent cycling of the cells, which provides insights into the interdependencies of different degradation modes induced by specific stress conditions. In this manner, it is clarified whether or not the total degradation can be determined by a convolution or a superposition of individual deterioration effects and thus, be described as a multidimensional state function. This knowledge will finally contribute to a better understanding of the performance and safety behavior of degraded batteries which can help to successfully implement them into second-life applications. T2 - Doktorandenseminar der Technischen Universität Berlin CY - Berlin, Germany DA - 30.09.2025 KW - Alkali metal-ion batteries KW - Electrochemical performance indicators PY - 2025 AN - OPUS4-65068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leonhardt, Robert T1 - Characterization of overdischarge-related degradation in commercial sodium-ion cells N2 - Sodium-ion batteries (SIBs) have recently gained significant attention as a cost-effective and sustainable alternative to lithium-ion batteries for large-scale energy storage applications and battery-electric vehicles. With their ability to be fully discharged to 0 V, they allow much safer handling and transport. The reversibility of such a complete discharge is, however, debated as the solid electrolyte interphase (SEI) formed by commonly used electrolytes in SIBs becomes unstable at low full-cell voltages. In the present study, the effects of overdischarging SIBs and the implications on their long-term impedance degradation are investigated for commercial SIB-cells, comprising sodium nickel manganese iron oxide (NaNi0.33Mn0.33Fe0.33O2) as cathode active material. During the study, extensive characterization measurements (e.g., electrochemical impedance spectroscopy, open-circuit voltage analysis, etc.) were performed at various stages of degradation. This allows the monitoring of the electrochemical characteristics of the tested SIBs. Notably, the long-term degradation behavior of the cells was significantly affected, indicating lasting changes in the passivating properties of the altered SEI. Finally, the results show that overdischarging can indeed cause irreversible changes in sodium-ion batteries, emphasizing the need to enhance their stability at low full-cell voltages to make the best possible use of their potential safety features. T2 - SBS6 – International Sodium Battery Symposium CY - Dresden, Germany DA - 03.09.2025 KW - Overdischarge of sodium ion batteries KW - Solid electrolyte interphase KW - Impedance spectroscopy KW - Battery degradation and aging PY - 2025 AN - OPUS4-65066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leonhardt, Robert T1 - Deconvoluting the impact of early-life abuse conditions on the degradation of lithium-ion cells N2 - The successful repurposing of degraded lithium-ion (Li-ion) batteries in second-life applications is a vital step towards achieving a circular economy. While reusing aged Li-cells is a promising way of mitigating their overall environmental footprint, it is crucial to anticipate their future safety and performance characteristics . Unfortunately, predicting these properties is a cumbersome task, essentially caused by limited knowledge of the interference of different degradation modes in the cells’ first life. To still enable estimating of these parameters from a current state, the present study systematically investigates the impacts of abusive conditions in an early phase of the cells’ life on their subsequent degradation behavior. For this purpose, individual Li-cells are initially stressed by different measures such as overcharging, deep-discharging, plating, and deliberate combinations of the aforementioned methods. Electrochemical performance indicators are monitored during subsequent cycling of the cells which provides insights into the interdependencies of different degradation modes induced by specific stress conditions. In this manner, it is clarified whether or not the total degradation can be determined by a convolution or a superposition of individual deterioration effects and, thus, be described as a multidimensional state function. This knowledge will finally contribute to a better understanding of the performance and safety behavior of degraded Li-ion batteries which can help to successfully implement them into second-life applications. T2 - ECS Gothenburg CY - Gothenburg, Sweden DA - 08.10.2023 KW - Li-ion batteries KW - Early-life overstress KW - Ageing PY - 2023 AN - OPUS4-59221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -