Lithium heterogeneities in cylinder-type Li-ion batteries – fatigue induced by cycling

Petz, Dominik; Mühlbauer, Martin; Baran, Volodymyr; Frost, Matthew; Schökel, Alexander; Paulmann, Carsten; Chen, Yan; Garcés, Diana; Senyshyn, Anatoliy

doi:10.1016/j.jpowsour.2019.227466

Cited by 28 publications

(34 citation statements)

References 55 publications

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“…Similar regions occur at the beginning and the end of each electrode stripe due to missing electrode coatings. [32] (II) cells with electrode connections according to Scheme 1 and 2 display the most uniform lithium distributioncharacterized by a clearly defined 2D plateau behavior; (III) lithium non-uniformities at the center of the electrode stripes are observed for cells with electrode connection of Scheme 2 and 3, where the area of the observed nonuniformities was quite different. Observation (III) is to a large extent affected by the spatial resolution of the experimental setup.…”

Section: Resultsmentioning

confidence: 96%

“…In Ref. [32], several statistical parameters were proposed to characterize the observed 2D distribution, namely the mean value and its standard deviation describing the average lithium concentration < x Li > , the median of the distribution and the plateau value x p . As recently shown, these statistic indicators perform well for a set of variously aged cells belonging to a common cell type and the same batch.…”

Section: Resultsmentioning

confidence: 99%

“…[17] Such kind of in situ neutron diffraction studies are performed on Li-ion cells of different designs, either laboratory [18][19][20][21] or commercial [22][23][24] type. In recent years a number of neutron diffraction studies dedicated to the lithiation of either positive or negative electrode materials, [25][26][27][28][29][30][31] aging behavior [32,33] and effects of temperature. [34,35] The majority of the above-mentioned reports focuses on the structure evolution obtained by integration over a large cell volume, assuming the studied cells to be uniform.…”

Section: Introductionmentioning

confidence: 99%

“…A method for probing the 2D lithium distribution in the graphite anode using monochromatic neutron diffraction (alternative to time-of-flight neutron diffraction) was proposed in literature. [38] The method was successfully applied to monitor the lithium distribution in four 18650-type cells adopting different configurations of current tabs [14] and to probe the lithium distribution in variously fatigued high energy lithium cobalt oxide LCO j C [39] and high performance lithium nickel cobalt aluminum Oxide NCA j C [32] cells. Recently, an attempt to localize and quantify the electrolyte in frozen state was made by a similar experimental approach at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Heterogeneity of Graphite Lithiation in State‐of‐the‐Art Cylinder‐Type Li‐Ion Cells

Petz

Mühlbauer

Schökel

et al. 2021

Batteries & Supercaps

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The two-dimensional lithium distribution in the graphite anode was non-destructively probed by spatially resolved neutron diffraction for a batch consisting of 34 different cylinder-type (18650) Li-ion batteries in fully charged state. The uniformity of the lithium distribution was quantified and correlated to the cell specifications/electrochemistry and to intrinsic cell parameters like electrode thickness, position of current collectors, etc. which were obtained by X-ray micro-computed tomography. Non-uniformities in the lithiation state of the anode from a constant plateau have been observed for the majority of the studied cells. Their location corresponds to the positions of current tabs connecting the electrode stripes and areas of incomplete electrode coating at the beginning and the end of the electrode stripes. Four commonly used schemes of current lid connection were identified. Each of them displays its own effect on the uniformity of the lithiation at the anode and, therefore, variation of the intrinsic state-of-charge distribution and, most probably, the ageing behavior of the electrodes.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Heterogeneity of Graphite Lithiation in State‐of‐the‐Art Cylinder‐Type Li‐Ion Cells

Petz

Mühlbauer

Schökel

et al. 2021

Batteries & Supercaps

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“…This rule out any electrode-wide source for the second stage. A possible explanation is that it might still happen locally because of inhomogeneities in the electrode degradation [61]. The origin of the apparent RDF increase is still unclear.…”

Section: Discussionmentioning

confidence: 99%

Durability and Reliability of EV Batteries Under Electric Utility Grid Operations: Impact of Frequency Regulation Usage on Cell Degradation

2020

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The usage of electric vehicle batteries to assist the main electric grid for the storage of energy provided by intermittent sources should become an essential tool to increase the penetration of green energies. However, this service induces additional usage on the cells and, therefore, could degrade them further. Since degradation is path-dependent, it is of paramount importance to test the impact of all the different grid applications on the batteries. In this work, we tested the additional usage induced by using electric vehicle batteries for frequency regulation at moderate rates during rest or charge and found no detrimental effect after around 2000 cycles on the cells. The main takeaway from our study was that some frequency regulation V2G usage at moderate rates (from C/5 to C/3 as a maximum current) did not accelerate the cell degradation despite close to 15% additional usage. In addition, there was no noticeable difference between performing this ancillary service during rest or charge or at maximum current fluctuations up to C/3 during rest and C/4 during charge. These results are extremely positive for the possible application of V2G/G2V strategies. However, it must be noted that our results hold for these specific cells and the duty cycle tested. More research is necessary to generalize the results. We already verified the results on another batch of commercial cells based on graphite//Nickel Cobalt Aluminum oxide. Due to the lack of differences in the degradation between duty cycles, the benefits of modulating the charge to eliminate the additional usage on the cells could not be verified. Experiments on other chemistries with more aggressive usage will be launched to test the hypothesis further. As for the diagnosis for the degradation, a new approach of coupling IC and DV analysis yielded four indicators for automatic diagnosis. This methodology will allow faster diagnosis and bolsters the value of the FOI approach for BMS implementation. However, our study also showed that under some conditions, in our case the apparent kinetic limitations, some of the FOI may become ineffective with time. Therefore, proper validation using full fits and sensibility analysis to check for the range of efficacy of chosen FOI is still essential. Finally, some cells showcased the 2nd stage of aging and we were not able to predict it from the voltage variations. This suggested that it was not induced by a widespread degradation of the electrodes but was more likely because of localized effects. The cells that did not perform any frequency regulation seemed to be the most affected, but those results need to be moderated by the fact that the differences were probably within what to expect between cells performing the same duty cycles.

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Aging‐Driven Composition and Distribution Changes of Electrolyte and Graphite Anode in 18650‐Type Li‐Ion Batteries

Petz

Baran

Peschel

et al. 2022

Advanced Energy Materials

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A series of low‐temperature studies on LiNi0.80Co0.15Al0.05O2 18650‐type batteries of high‐energy type with different stabilized states of fatigue is carried out using spatially resolved neutron powder diffraction, infrared/thermal imaging, and quasi‐adiabatic calorimetry. In‐plane distribution of lithium in the graphite anode and frozen electrolyte in fully charged state is determined non‐destructively with neutron diffraction and correlated to the introduced state of fatigue. An independent electrolyte characterization is performed via calorimetry studies on variously aged 18650‐type lithium‐ion batteries, where the shape of the thermodynamic signal is evolving with the state of fatigue of the cells. Analyzing the liquid electrolyte extracted/harvested from the studied cells reveals the decomposition of conducting salt to be the main driving factor for fatigue in the electrolyte degradation.

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Lithium heterogeneities in cylinder-type Li-ion batteries – fatigue induced by cycling

Cited by 28 publications

References 55 publications

Heterogeneity of Graphite Lithiation in State‐of‐the‐Art Cylinder‐Type Li‐Ion Cells

Heterogeneity of Graphite Lithiation in State‐of‐the‐Art Cylinder‐Type Li‐Ion Cells

Durability and Reliability of EV Batteries Under Electric Utility Grid Operations: Impact of Frequency Regulation Usage on Cell Degradation

Aging‐Driven Composition and Distribution Changes of Electrolyte and Graphite Anode in 18650‐Type Li‐Ion Batteries

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