Long-Term Self-Discharge Measurements and Modelling for Various Cell Types and Cell Potentials

Mohamed Azzam (), Moritz Ehrensberger, Reinhard Scheuer, Christian Endisch and Meinert Lewerenz ()
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Mohamed Azzam: Research Group Electromobility and Learning Systems, Technische Hochschule Ingolstadt, D-85049 Ingolstadt, Germany
Moritz Ehrensberger: Research Group Electromobility and Learning Systems, Technische Hochschule Ingolstadt, D-85049 Ingolstadt, Germany
Reinhard Scheuer: Research Group Electromobility and Learning Systems, Technische Hochschule Ingolstadt, D-85049 Ingolstadt, Germany
Christian Endisch: Research Group Electromobility and Learning Systems, Technische Hochschule Ingolstadt, D-85049 Ingolstadt, Germany
Meinert Lewerenz: Research Group Electromobility and Learning Systems, Technische Hochschule Ingolstadt, D-85049 Ingolstadt, Germany

Energies, 2023, vol. 16, issue 9, 1-19

Abstract: Self-discharge of lithium-ion cells leads to voltage decay over time. In this work, the self-discharge was measured at 30 ∘ C for three cell types at various voltage levels for about 150 days in a constant voltage mode determining the current at a high precision (float current). All cells exhibit a transient part leading to a steady-state, which is no longer influenced by reversible effects. To study the effect of the check-ups on the steady-state float current, the cells, interrupted and not interrupted by check-ups, were compared. The results indicate that both the transient processes and steady-state currents are highly reproducible. In the first period of the float current, the polarization dominates the measured current, followed by the anode overhang effect dominating the process for a period of 5–30 days. After the decline of both processes, a mostly constant steady-state in the order of μ A is observed. The check-up interruption generally shows no apparent effect on the reached steady-state and results only in an extended settling time. A model to simulate the transient process and steady-state of float currents was developed. The model shows a high accuracy in reproducing the results and identifying the time needed to reach the steady-state.

Keywords: 18650; NCA; NMC; LFP; graphite; float current analysis; potentiostatic hold; self-discharge rate; modelling; filtering; anode overhang (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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