@article{AzzamAydinEndischetal.2025, author = {Azzam, Mohamed and Aydin, Atakhan and Endisch, Christian and Sauer, Dirk Uwe and Lewerenz, Meinert}, title = {Float Current Analysis for Lithium-Ion Battery Aging: Insights into SEI Growth and Cathode Lithiation with EIS and ICP OES}, volume = {172}, pages = {070529}, journal = {Journal of The Electrochemical Society}, number = {7}, publisher = {IOP Publishing}, address = {Bristol}, issn = {1945-7111}, doi = {https://doi.org/10.1149/1945-7111/adef85}, year = {2025}, abstract = {This study investigates calendar-aging mechanisms in lithium-ion batteries, focusing on cathode lithiation due to decomposition of conductive salt and SEI growth, by correlating quantified float currents, capacity loss rates, and pulse resistances with changes in electrochemical impedance spectroscopy (EIS) spectra. Seven SamSung 25 R cells are aged at different float voltages with periodic EIS measurements at 30 °C. Using a pre-characterization cell, the internal processes via EIS are allocated across various states of charge and temperatures and GITT measurements are performed to derive scaling factors. GITT, float currents and capacity loss rate measurements at 30 °C enables the separation of SEI growth ISEI growth and cathode lithiation current ICL based on float current behavior across a temperature range of 5 °C to 50 °C. The distribution of relaxation times (DRT) method is employed to deconvolute overlapping electrochemical processes. EIS and DRT analyses showed significant changes in cathode charge transfer resistance and diffusion, confirming that cathode lithiation correlates substantially to elevated internal resistance at high cell voltages. The theory of ISEI growth and ICL is further supported using inductively coupled plasma atomic emission spectroscopy by quantifying elemental inventory changes and linking phosphorus release and lithium consumption to degradation mechanisms.}, language = {en} } @article{AzzamEhrensbergerEndischetal.2024, author = {Azzam, Mohamed and Ehrensberger, Moritz and Endisch, Christian and Sauer, Dirk Uwe and Lewerenz, Meinert}, title = {Comparison of dU/dQ, Voltage Decay, and Float Currents via Temperature Ramps and Steps in Li-ion Batteries}, volume = {8}, pages = {e202400627}, journal = {Batteries \& Supercaps}, number = {1}, publisher = {Wiley}, address = {Weinheim}, issn = {2566-6223}, doi = {https://doi.org/10.1002/batt.202400627}, year = {2024}, language = {en} } @article{PaarmannSchreiberChahbazetal.2024, author = {Paarmann, Sabine and Schreiber, Markus and Chahbaz, Ahmed and Hildenbrand, Felix and Stahl, Gereon and Rogge, Marcel and Dechent, Philipp and Queisser, Oliver and Frankl, Sebastian Dominic and Morales Torricos, Pablo and Lu, Yao and Nikolov, Nikolay I. and Kateri, Maria and Sauer, Dirk Uwe and Danzer, Michael A. and Wetzel, Thomas and Endisch, Christian and Lienkamp, Markus and Jossen, Andreas and Lewerenz, Meinert}, title = {Short-Term Tests, Long-Term Predictions - Accelerating Ageing Characterisation of Lithium-Ion Batteries}, volume = {7}, pages = {e202300594}, journal = {Batteries \& Supercaps}, number = {11}, publisher = {Wiley}, address = {Weinheim}, issn = {2566-6223}, doi = {https://doi.org/10.1002/batt.202300594}, year = {2024}, abstract = {AbstractFor the battery industry, quick determination of the ageing behaviour of lithium-ion batteries is important both for the evaluation of existing designs as well as for R\&D on future technologies. However, the target battery lifetime is 8-10 years, which implies low ageing rates that lead to an unacceptably long ageing test duration under real operation conditions. Therefore, ageing characterisation tests need to be accelerated to obtain ageing patterns in a period ranging from a few weeks to a few months. Known strategies, such as increasing the severity of stress factors, for example, temperature, current, and taking measurements with particularly high precision, need care in application to achieve meaningful results. We observe that this challenge does not receive enough attention in typical ageing studies. Therefore, this review introduces the definition and challenge of accelerated ageing along existing methods to accelerate the characterisation of battery ageing and lifetime modelling. We systematically discuss approaches along the existing literature. In this context, several test conditions and feasible acceleration strategies are highlighted, and the underlying modelling and statistical perspective is provided. This makes the review valuable for all who set up ageing tests, interpret ageing data, or rely on ageing data to predict battery lifetime.}, language = {en} } @article{LewerenzRaheFuchsetal.2020, author = {Lewerenz, Meinert and Rahe, Christiane and Fuchs, Georg and Endisch, Christian and Sauer, Dirk Uwe}, title = {Evaluation of shallow cycling on two types of uncompressed automotive Li(Ni1/3Mn1/3Co1/3)O2-Graphite pouch cells}, volume = {2020}, pages = {101529}, journal = {Journal of Energy Storage}, number = {30}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2352-1538}, doi = {https://doi.org/10.1016/j.est.2020.101529}, year = {2020}, language = {en} } @article{AzzamSauerEndischetal.2025, author = {Azzam, Mohamed and Sauer, Dirk Uwe and Endisch, Christian and Lewerenz, Meinert}, title = {Comprehensive Analysis of Float Current Behavior and Calendar Aging Mechanisms in Lithium-Ion Batteries}, volume = {9}, pages = {e202500349}, journal = {Batteries \& Supercaps}, number = {1}, publisher = {Wiley}, address = {Weinheim}, issn = {2566-6223}, doi = {https://doi.org/10.1002/batt.202500349}, year = {2025}, abstract = {Aiming to quantify degradation currents from solid electrolyte interphase formation (ISEIgrowth) and gain of active lithium due to cathode lithiation (ICL), resulting from electrolyte decomposition, the float current behavior of lithium-ion batteries is investigated with different cathode materials. The float current, IFloat , represents the recharge current required to maintain the cell at a fixed potential during calendar aging. This current arises as lithium is irreversibly consumed at the anode or inserted into the cathode, shifting the electrode potentials. To account for the asymmetric response of the electrodes, a voltage-dependent scaling factor, SF, is introduced, derived from the slopes of the electrode-specific voltage curves. Using this factor in combination with measured float currents and capacity loss rates from check-up tests, ISEIgrowth and ICL is quantified at 30 °C across various float voltages. Although the SF and capacity data are limited to 30 °C, the model is extended to a range of 5-50 °C using only float current measurements. The results show that using capacity loss rates alone underestimate ISEIgrowth and that ICL, contributes significantly to the observed float current at elevated voltages, indicating that cathode lithiation plays an increasingly important role in high-voltage calendar aging.}, language = {en} }