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Focus:

  • Floater hardware development
  • Research of float current analysis on battery cells
  • Development of ideal measurement routines
  • Automation for accelerated application
  • Modeling of aging

Summary:

The young research group I-BasE has set itself the goal of developing new industry-relevant test strategies for lithium-ion cells in an interdisciplinary and international team, which consider reversible capacity effects and additional effects due to the acceleration of aging tests.

For this purpose, quasi-static self-discharge currents - called float currents - are investigated, which show a strong correlation to the capacity loss of the cells. Particularly attractive is the fast and direct measurement of aging, which, among other things, leads to a rapid characterization. By integrating electrochemical impedance spectroscopy (EIS), additionally resistances can be measured at low noise.

This will increase the prediction quality and at the same time shorten the testing time for domestic enterprises. Due to the inexpensive, comprehensive and fast characterization of the cells, they can be selected more precisely to save costs and accelerate innovation cycles.

The project has a total volume of 2.2 million euros and includes 4-5 research assistants over 5 years.

Relevant literature:

Publications float currents

  • I. Kiran, M. Azzam, C. Endisch, N. Z. Butt, M. Lewerenz, Evaluation of Calendar Aging in Cells with Graphite: Silicon Anode Using Float Current Analysis Under the Influence of Voltage Hysteresis, Journal of Electrochemical Society, Volume 172, Number 10 (2025). doi: 10.1149/1945-7111/ae0fe8.
  • M. Azzam, D.-U. Sauer, C. Endisch, M. Lewerenz, Comprehensive Analysis of Float Current Behavior and Calendar Aging Mechanisms in Lithium-Ion Batteries, Batteries & Supercaps (2025), e202500349. https://doi.org/10.1002/batt.202500349.
  • M. Azzam, A. Aydin, C. Endisch, D.-U. Sauer, M. Lewerenz, Float Current Analysis for Lithium-Ion Battery Aging: Insights into SEI Growth and Cathode Lithiation with EIS and ICP OES, Journal of The Electrochemical Society, Volume 172, Number 7 (2025). doi: 10.1149/1945-7111/adef85.
  • Q. Yu, I. Kiran, M. Ehrensberger, L. Streck, T. Roth, A. Jossen, C. Endisch, M. Lewerenz, Assigning Calendar Aging during Open Circuit and Float Current Analysis to Anode and Cathode Aging Using Three-Electrode Cells, Journal of The Electrochemical Society, Volume 172, Number 6 (2025). doi: 10.1149/1945-7111/ade295.
  • M. Azzam, M. Ehrensberger, C. Endisch, D.-U. Sauer, M. Lewerenz, Comparison of dU/dQ, Voltage Decay, and Float Currents via Temperature Ramps and Steps in Li-ion Batteries, Batteries & Supercaps (2024), e202400627. https://doi.org/10.1002/batt.202400627.
  • M. Azzam, M. Ehrensberger, C. Endisch, M. Lewerenz, Accelerating float current measurement with temperature ramps revealing entropy insights, Journal of Energy Storage, Volume 102, Part B (2024). https://doi.org/10.1016/j.est.2024.114142.
  • M. Azzam, C. Endisch, M. Lewerenz, Evaluating the Aging-Induced Voltage Slippery as Cause for Float Currents of Lithium-ion Cells, Batteries 10(1) (2024) 3. https://doi.org/10.3390/batteries10010003.
  • M. Azzam, M. Ehrensberger, R. Scheuer, C. Endisch, M. Lewerenz, Long-Term Self-Discharge Measurements and Modelling for Various Cell Types and Cell Potentials, Energies 16(9) (2023) 3889. https://doi.org/10.3390/en16093889.
  • M. Theiler, C. Endisch and M. Lewerenz, Float Current Analysis for Fast Calendar Aging Assessment of 18650 Li(NiCoAl)O2/Graphite Cells, Batteries 7 (2021) 22. https://doi.org/10.3390/batteries7020022.
  • M. Lewerenz, J. Münnix, J. Schmalstieg, S. Käbitz, M. Knips, A. Warnecke, D.U. Sauer, New method evaluating currents keeping the voltage constant for fast and high resolved measurement of Arrhenius relation and capacity fade, J. Power Sources 353 (2017) 144–151. https://doi:10.1016/j.jpowsour.2017.03.136.

Publications homogeneity

  • M. Lewerenz, P. Dechent, D.U. Sauer, Investigation of capacity recovery during rest period at different states-of-charge after cycle life test for prismatic Li(Ni1/3Mn1/3Co1/3)O2-graphite cells, Journal of Energy Storage 21 (2019) 680–690. https://doi.org/10.1016/j.est.2019.01.004.
  • M. Lewerenz, D.U. Sauer, Evaluation of cyclic aging tests of prismatic automotive LiNiMnCoO2-Graphite cells considering influence of homogeneity and anode overhang, Journal of Energy Storage 18 (2018) 421–434. https://doi.org/10.1016/j.est.2018.06.003.
  • M. Lewerenz, G. Fuchs, L. Becker, D.U. Sauer, Irreversible calendar aging and quantification of the reversible capacity loss caused by anode overhang, Journal of Energy Storage 18 (2018) 149–159. https://doi.org/10.1016/j.est.2018.04.029.
  • M. Lewerenz, A. Marongiu, A. Warnecke, D.U. Sauer, Differential voltage analysis as a tool for analyzing inhomogeneous aging: a case study for LiFePO4|Graphite cylindrical cells, J. Power Sources 368 (2017) 57–67. https://doi:10.1016/j.jpowsour.2017.09.059.
  • M. Lewerenz, A. Warnecke, D.U. Sauer, Introduction of capacity difference analysis (CDA) for analyzing lateral lithium-ion flow to determine the state of covering layer evolution, J. Power Sources 354 (2017) 157–166. https://doi.org/10.1016/j.jpowsour.2017.04.043.

Publications overhang effect

  • M. Lewerenz, J. Münnix, J. Schmalstieg, S. Käbitz, M. Knips, D.U. Sauer, Systematic aging of commercial LiFePO4jGraphite cylindrical cells including a theory explaining rise of capacity during aging, J. Power Sources 345 (2017) 254–263. https://doi:10.1016/j.jpowsour.2017.01.133.
  • M. Lewerenz, G. Fuchs, L. Becker, D.U. Sauer, Irreversible calendar aging and quantification of the reversible capacity loss caused by anode overhang, Journal of Energy Storage 18 (2018) 149–159. https://doi.org/10.1016/j.est.2018.04.029.
  • M. Lewerenz, P. Dechent, D.U. Sauer, Investigation of capacity recovery during rest period at different states-of-charge after cycle life test for prismatic Li(Ni1/3Mn1/3Co1/3)O2-graphite cells, Journal of Energy Storage 21 (2019) 680–690. https://doi.org/10.1016/j.est.2019.01.004.

Contact

Funding

This project is funded by the German Federal Ministry of Education and Research within the framework of the announcement "BattFutur" (grant number 03XP0442).

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