Modeling the self-discharge by voltage decay of a NMC/graphite lithium-ion cell

Deutschen, Thomas; Gasser, Sophie; Schaller, Manuel; Siehr, Jochen

doi:10.1016/j.est.2018.07.003

Cited by 25 publications

(20 citation statements)

References 9 publications

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“…Based on the OCV from the previous intermediate characterization x − 1, an SoC value is assigned to each voltage value according to Equation (2). The approach is comparable to the long-time model equations for self-discharge presented by Deutschen et al [35].…”

Section: Self-discharge During Storagementioning

confidence: 99%

“…The resulting voltage drift is equivalent to a changing SoC during storage. The exponential decay model approach by Deutschen et al is suitable to describe the voltage course for short-and long-time storage periods [35]. Similarly, Redondo et al described the selfdischarge with an exponential decay model for the cell leakage current during storage over time [27].…”

Section: Introductionmentioning

confidence: 99%

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Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation

2021

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The lifetime of the battery significantly influences the acceptance of electric vehicles. Calendar aging contributes to the limited operating lifetime of lithium-ion batteries. Therefore, its consideration in addition to cyclical aging is essential to understand battery degradation. This study consequently examines the same graphite/NCA pouch cell that was the subject of previously published cyclic aging tests. The cells were aged at different temperatures and states of charge. The self-discharge was continuously monitored, and after each storage period, the remaining capacity and the impedance were measured. The focus of this publication is on the correlation of the measurements. An aging correlation is obtained that is valid for a wide range of temperatures and states of charge. The results show an accelerated capacity fade and impedance rise with increasing temperature, following the law of Arrhenius. However, the obtained data do also indicate that there is no path dependency, i.e., earlier periods at different temperature levels do not affect the present degradation rate. A large impact of the storage state of charge at 100% is evident, whereas the influence is small below 80%. Instead of the commonly applied square root of the time function, our results are in excellent agreement with an exponential function.

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Section: Self-discharge During Storagementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation

2021

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“…According to the time samples of the network frequency, we consider its value of 1440 per day. In our simulation of NMC cell degradation, we determined to calculate with 0.15% self-discharging per 24 h due to the acknowledgements and methods from the study of the self-discharge principles of NMC Li-ion cells by Thomas Deutschen et al [43].…”

Section: Pdb P Of P Gc P Etmentioning

confidence: 99%

Second Life Batteries Used in Energy Storage for Frequency Containment Reserve Service

Janota¹,

Králík²,

Knápek³

2020

Energies

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The new Li-ion battery systems used in electric vehicles have an average capacity of 50 kWh and are expected to be discarded when they reach approximately 80% of their initial capacity, because they are considered to no longer be sufficient for traction purposes. Based on the official national future development scenarios and subsequent mathematical modeling of the number of electric vehicles (EVs), up to 400 GWh of storage capacity in discharged batteries will be available on the EU market by 2035. Therefore, since the batteries still have a considerable capacity after the end of their first life, they could be used in many stationary applications during their second life, such as support for renewables, flexibility, energy arbitrage, peak shaving, etc. Due to the high output power achieved in a short time, one of the most promising applications of these batteries are ancillary services. The study assesses the economic efficiency of the used batteries and presents several main scenarios depending on the likely future development of the interconnected EU regulatory energy market. The final results indicate that the best results of second-life batteries utilization lie in the provision of Frequency Containment Reserve Service, both from a technical and economic point of view. The internal rate of return fluctuates from 8% to 21% in the realistic scenario, and it supports the idea that such systems might be able to be in operation without any direct financial subsidies.

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“…Theoretically, the overpotential during the potentiostatic float current measurement could trigger a reaction and is not existing during open circuit storage. For SOC of about 75% at 25 • C and about 90% at 60 • C, Deutschen et al [26] showed self-discharge losses during open circuit storage that stabilize after long measurement. The equivalent float current calculated from the constant loss by self-discharge neglecting the transient part is in the order of 0.5%/100 days and 5.0%/100 days and fits to results reported in the literature [3] for comparable chemistries excluding anode overhang effect.…”

Section: Introductionmentioning

confidence: 99%

Float Current Analysis for Fast Calendar Aging Assessment of 18650 Li(NiCoAl)O2/Graphite Cells

2021

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Float currents are steady-state self-discharge currents after a transient phase—caused by anode overhang, polarization, etc.—is accomplished. The float current is measured in this study with a standard test bench for five 18650 cells (Samsung 25R) at potentiostatic conditions while the temperature is changed in 5 K steps from 5 °C to 60 °C. The entire test is performed in about 100 days resulting in 12 measurement points per cell potential for an Arrhenius representation. The float current follows the Arrhenius law with an activation energy of about 60 kJ/mol. The capacity loss measured at reference condition shows a high correlation to the results of float currents analysis. In contrast to classical calendar aging tests, the performed float current analysis enables determining the aging rate with high precision down to at least 10 °C. Returning from higher temperatures to 30 °C reference temperature shows reducing float currents at 30 °C for increasing temperature steps that may originate from an hysteresis effect that has to be investigated in future publications.

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Modeling the self-discharge by voltage decay of a NMC/graphite lithium-ion cell

Cited by 25 publications

References 9 publications

Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation

Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation

Second Life Batteries Used in Energy Storage for Frequency Containment Reserve Service

Float Current Analysis for Fast Calendar Aging Assessment of 18650 Li(NiCoAl)O2/Graphite Cells

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