The longevity of lithium-ion batteries (LIBs) is greatly affected by ageing. Therefore, models are required to accurately describe their degradation behaviour. Given the complex processes involved in battery ageing [1], identifying suitable parameters is a significant challenge in model development [2]. This study focuses on the loss of cyclable lithium due to the binding of lithium ions in the solid electrolyte interphase (SEI), which is one of the main ageing effects in LIBs [3]. This work validates the SEI model and parameterization approach proposed by Schomburg et al. [2] through the application of Differential Voltage Analysis (DVA).

The experiments were carried out with experimental NMC622 | Gr cells. We parameterized the SEI model using the anode potential of three-electrode-cells [3] and validated them by performing storage tests with coin cells at elevated temperatures and variation in SOC. The parameters were identified by performing DVA with the anode potential of the formation to identify the SEI growth. The model was fitted based on this experimentally determined growth. For validation, a pseudo-OCV curve was recorded every four weeks at 0.05 C for the coin cells to measure the current capacity by Coulomb Counting and to perform DVA with the full cell voltage. The anode potential was assumed to be constant over the storage time. The model achieves a high level of agreement for high SOCs during storage but significantly underestimates ageing at low SOCs. This indicates that the methodology is applicable for the parameterization of the SEI model, although the causes for these deviations need to be addressed.

To conclude, the presented methods address the parameterization of SEI models with minimum time expenditure and allow predictions to be made about the ageing of the LIBs. The SEI-growth-induced ageing can be investigated without storage tests, thereby reducing the required resources. Future work will investigate multiple ageing mechanisms and their interplay by using dynamic ageing studies, where SEI growth and lithium plating are triggered in consecutive sequences.

[1] J. Keil and A. Jossen, Electrochemical Modeling of Linear and Nonlinear Aging of Lithium-Ion Cells, Electrochem. Soc. 2020, 167, 110535, DOI: 10.1149/1945-7111/aba44f
[2] F. Schomburg et al., Characterization of the Solid–Electrolyte Interphase Growth During Cell Formation Based on Differential Voltage Analysis, Energy Technol. 2023, 11, 2200688,
DOI: 10.1002/ente.202200688
[3] J. S. Edge et al., Lithium ion battery degradation: what you need to know, Phys. Chem. Chem. Phys. 2021, 23, 8200, DOI: 10.1039/D1CP00359C