In the last years, there were a lot of new research articles and findings that question state-of-the-art accelerated aging tests and their meaning for the assessment of aging and the accuracy of lifetime prediction. Standard accelerated aging tests increase stress factors such as C-rate and reduce idle periods to zero compared to the dedicated long-life application.
Lewerenz et al. [1] found that capacity lost during cycling is to a high extent recoverable during a subsequent long rest phase. It is associated with a reduction of homogeneity of lithium distribution (HLD) on the anode side. It appears in a flattening and recovering of graphite features in the differential voltage analysis and in a rise and decay in the capacity difference analysis (CDA) [2]. This apparent aging was found in later publications for various cathode materials and as well for silicon graphite composites on the anode [1,3,4]. This questions the use of data from classical accelerated aging tests to predict the lifetime in a long-life application.
Other groups found lately a high impact of the electrolyte to the aging. Aiken et al. [5] and Bond et al. [6] demonstrated for different cells and experimental setups that during charge and discharge the electrolyte is pumped out of the jelly roll soaked back in. Solchenbach et al. [7] found that this continuous pumping effect accompanied with polarization of the electrolyte leads to an inhomogeneous distribution of the conductive salt making this electrode area prone to lithium plating. The so-called Electrolyte Motion by Salt Inhomogeneity-Effect (EMSI). Morales Torricos et al. [8] further assigned that the apparent aging is further linked to a change in volume in the anode and to a stiff housing or external compression.
In this lecture, the different findings regarding apparent aging, loss of HLD and EMSI-effect are linked into one mechanistic model including contributions e.g. to resistance (Shown in the provided figure). Additionally, new measurement results for 8 stiff compressed Lifun Pouch cell (NMC532/ graphite) anode cells at two offset pressures varying charge and discharge currents are presented. The influence of the magnitude of charge and discharge currents are discussed including the influence of resistive heat as a side effect of high C-rate cycling. We found a strong impact of temperature on the EMSI and the apparent aging effect and could enhance the understanding of our mechanistic model.
[1] 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 Ener-gy Storage 21 (2019) 680–690. https://doi.org/10.1016/j.est.2019.01.004.
[2] 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, Journal of Power Sources 354 (2017) 157–166. https://doi.org/10.1016/j.jpowsour.2017.04.043.
[3] M. Schreiber, Y. Lin, A. Sommer, N. Wassiliadis, P.M. Torricos, m. Rogge, M. Lewerenz, C. Grosu, C. Endisch, A. Jossen, M. Lienkamp, Apparent vs. true battery aging: Impact of various load characteristics on accelerated aging tests, Journal of Energy Storage 127 (2025) 116924. https://doi.org/10.1016/j.est.2025.116924
[4] P. Morales Torricos, C. Endisch, M. Lewerenz, Apparent Aging during Accelerated Cycling Aging Test of Cylindrical Silicon Containing Li-Ion Cells, Batteries 9 (4) (2023) 230. https://doi.org/10.3390/batteries9040230.
[5] C.P. Aiken, N. Kowalski, R.C. Fitzner, S. Trussler, J.E. Harlow, E.J. Butler, J.R. Dahn, Tracking Electrolyte Mo-tion in Cylindrical Li-ion Cells Using Moment of Inertia Measurements, J. Electrochem. Soc. 170 (2023) 40529. https://doi.org/10.1149/1945-7111/acce72.
[6] T. Bond, S. Gasilov, R. Dressler, R. Petibon, S. Hy, J.R. Dahn, Operando 3D Imaging of Electrolyte Motion in Cylindrical Li-Ion Cells, J. Electrochem. Soc. 172 (2025) 30512. https://doi.org/10.1149/1945-7111/adba8f.
[7] S. Solchenbach, C. Tacconis, J. Wandt, Electrolyte motion Induced Salt Inhomogeneity – A Novel Aging mechanism in large-Format Litihum-Ion Cells (2024). https://doi.org/10.26434/chemrxiv-2024-xdx2q.
[8] P. Morales Torricos, S. Berg, E. Figgemeier, C. Endisch, M. Lewerenz, The important role of lithiation-induced pressure change on apparent aging of lithium-ion batteries during accelerated cyclic aging tests, Journal of Energy Storage, Volume 131, Part A (2025). https://doi.org/10.1016/j.est.2025.117323.