Cycling capacity recovery effect: A coulombic efficiency and post-mortem study

Wilhelm, Jörn; Seidlmayer, Stefan; Keil, Peter; Schuster, Jörg; Kriele, Armin; Gilles, Ralph; Jossen, Andreas

doi:10.1016/j.jpowsour.2017.08.090

Cited by 67 publications

(57 citation statements)

References 45 publications

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“…Because cells charged to 4.1V spend increased lengths of time at high SoC than those charged to 4.2 V, the cyclable lithium content will thus be influenced by the anode overhang areas, which correspond to the perimeter portions of the anode active material that do not have a direct cathode counterpart (see Figure 4). 24 They act as a lithium sink or a lithium source, depending on the voltage / SoC at which the cell is held. 25 Li flow between active and passive anode areas (sometimes referred to as "passive electrode" effect) is slow and equilibration occurs on the time scale of weeks (see Figure 3).…”

Section: Resultsmentioning

confidence: 99%

Communication—Identifying and Managing Reversible Capacity Losses that Falsify Cycle Ageing Tests of Lithium-Ion Cells

Burrell

Zulke

Keil³

et al. 2020

J. Electrochem. Soc.

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We report on a cycle ageing study of commercial NCA/Gr+Si cells, in which reversible capacity fluctuations turn a central experimental finding upside down: an upper voltage limit of 4.1 V seems to cause faster degradation than going all the way to 4.2 V. The underlying effect is the reversible loss of lithium inventory into passive anode overhang areas. We demonstrate how the resulting artefact arises from a combination of slow transport processes and the related time periods spent in specific state-of-charge regions. We propose an alternative visualisation tool to identify and manage such artefacts, often neglected in typical ageing studies.

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Section: Resultsmentioning

confidence: 99%

Communication—Identifying and Managing Reversible Capacity Losses that Falsify Cycle Ageing Tests of Lithium-Ion Cells

Burrell

Zulke

Keil³

et al. 2020

J. Electrochem. Soc.

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“…Or it could decrease effectively over the cell's lifetime due to aging effects such as loss of active material. Note, that an electrode overhang area, as reported by Wilhelm et al, 41 is neglected in this investigation on cell level. Moreover, A elec,neg = A elec, pos = A elec is considered the same for both electrodes and therefore varying this parameter in the model will not change the balancing of the two electrodes to each other.…”

Section: Influencing Parameters On Inhomogeneity In Battery Modulesmentioning

confidence: 99%

Influence of Cell-to-Cell Variations on the Inhomogeneity of Lithium-Ion Battery Modules

Rumpf

Rheinfeld

Schindler

et al. 2018

J. Electrochem. Soc.

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Inhomogeneity within lithium-ion battery modules can occur due to variations in capacity and impedance of the connected cells as well as due to thermal gradients or cell connector design. We present a model for describing xSyP battery modules during operation, which is able to study these effects. The multidimensional multiphysics model includes a physicochemical model describing the electrochemical behavior of each cell. The electrical model accounts for the conservation of electric charge and energy between the cells to reach electrical consistency according to the respective module topology and cell interconnections. The model is capable of investigating the influence of defective and asymmetric cell connectors on the inhomogeneity of module operation. To evaluate this electrical influence, the observed inhomogeneities are compared to the influence of thermal gradients between the cells. The resulting inhomogeneous current distribution is presented for a module of two parallel connected lithium iron phosphate-graphite cells under constant current discharge operation for variations in cell capacity, cell impedance and ambient temperature at different module contact scenarios. From the observed impact of both, electrical and thermal variations between parallel connected cells, a matching strategy is derived and discussed which can enhance a module's performance during e.g. second life applications.

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“…However, the interpretation of the spectrum is difficult at times and the information content regarding lithium plating is low [11,17]. As a post-mortem analysis, destructive cell openings under inert atmosphere are used for the unambiguous identification of metallic lithium, which becomes visible through a metallic-silver deposit on the graphite surface [18,33].…”

Section: Lithium Plating As a Potential Aging Mechanism While Chargingmentioning

confidence: 99%

“…To determine the discharge capacity C Dis,CCCV in step 3, two CCCV cycles with C/3 and a cut-off current of C/25 in charge and discharge direction are applied. The averaged discharge capacity is used as check-up capacity in order to minimize the influence of the recovery effect [33,34,36,37]. Finally, the internal resistance R DC,10s is determined by a two-stage pulse test in step 4.…”

Section: Regular Check-up Testmentioning

confidence: 99%

Investigation of the Effects of Charging Processes on Lithium-Ion Cells with SiC Anodes at Low Temperatures

Bednorz

Gewald

2020

Batteries

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Lithium-ion cells with a silicon-graphite (SiC) anode and a nickel-rich cathode are potential candidates for use in electric vehicles (EVs) as this material combination offers high energy densities and low costs. Another desired cell specification that results from an intended short charging time for EVs is the robustness against high charge rates. However, high charge rates can lead to the critical aging mechanism of lithium plating, especially at low temperatures. Investigating this issue, this paper presents a test series on cyclic aging with varying charge rates from 0.2C to 1.5C at ambient temperatures of 0 °C and 10 °C applied to a nickel-rich SiC cell candidate. The resulting effects on cell aging are analyzed with a stripping method, whereby reversible lithium plating can be detected, and a differential voltage analysis (DVA), whereby the overall loss of capacity can be attributed to changes in individual characteristic capacities. The results indicate a degradation sensitivity of SiC anodes at elevated charge rates, evidenced by the loss in the silicon-related characteristic capacity, and question the aging robustness of this material combination.

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Cycling capacity recovery effect: A coulombic efficiency and post-mortem study

Cited by 67 publications

References 45 publications

Communication—Identifying and Managing Reversible Capacity Losses that Falsify Cycle Ageing Tests of Lithium-Ion Cells

Communication—Identifying and Managing Reversible Capacity Losses that Falsify Cycle Ageing Tests of Lithium-Ion Cells

Influence of Cell-to-Cell Variations on the Inhomogeneity of Lithium-Ion Battery Modules

Investigation of the Effects of Charging Processes on Lithium-Ion Cells with SiC Anodes at Low Temperatures

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