18650 vs. 21700 Li-ion cells – A direct comparison of electrochemical, thermal, and geometrical properties

Waldmann, Thomas; Scurtu, Rares-George; Richter, Karsten; Wohlfahrt‐Mehrens, Margret

doi:10.1016/j.jpowsour.2020.228614

Cited by 98 publications

(74 citation statements)

References 35 publications

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“…In the formation (left hand side of Figure 3b), both tab designs show similar areal discharge capacities (except for one outlier). For higher C-rates differences become visible (compare Figure 3a), which is consistent with our previous direct comparisons with the same electrodes, electrolytes, and separators of pilot-line built 18,650 and 21,700 cells [5] as well as PHEV1, pouch, and 21,700 cells [14].…”

Section: Resultssupporting

confidence: 91%

“…Such inhomogeneities can lead to deformations of the jellyroll after long-term cycling, especially at increased C-rates [2,3]. This should be different if the tabs were constructed from the current collecting foils themselves (Figure 1d), since they lead to less disturbed and therefore more homogeneous jellyrolls, which are closer to the mathematically ideal shape of an Archimedean spiral [5].…”

Section: Introductionmentioning

confidence: 98%

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Increase of Cycling Stability in Pilot-Scale 21700 Format Li-Ion Cells by Foil Tab Design

et al. 2021

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Li-ion cells of the industrially-relevant 21700 format were built on pilot-scale with tabs made from (a) the electrodes’ current collecting foils (Al and Cu, “foil tabs”) in comparison with (b) conventional tabs (Al and Ni) welded to the electrodes’ current collecting foils (“welded tabs”). Both cell types use the same anode (graphite), cathode (NMC622), separator, electrolyte, as well as the same tab positions. This allows a direct comparison of welded tabs and foil tabs regarding formation, C-rate capability, cell electrical resistance, and long-term cycling stability tests. Our data reproducibly shows 14.4% longer cycling stability and 11.2% increased total charge throughput in the case of the cells with foil tabs until 80% SOH, which is likely due to less inhomogeneities in the case of the foil tab design.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 98%

Increase of Cycling Stability in Pilot-Scale 21700 Format Li-Ion Cells by Foil Tab Design

et al. 2021

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“…This enabled cell level degradation processes to be attributed to one (or both) electrodes. Various cylindrical cells from 1.5 A h 18650 to 5.0 A h 21700 cells have been compared in two studies [21,22]. The energy density depended on the areal capacities of the electrodes but not the cell size.…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Lithium-Ion Cell Performance across Three Different Cell Formats

et al. 2021

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To investigate the influence of cell formats during a cell development programme, lithium-ion cells have been prepared in three different formats. Coin cells, single layer pouch cells, and stacked pouch cells gave a range of scales of almost three orders of magnitude. The cells used the same electrode coatings, electrolyte and separator. The performance of the different formats was compared in long term cycling tests and in measurements of resistance and discharge capacities at different rates. Some test results were common to all three formats. However, the stacked pouch cells had higher discharge capacities at higher rates. During cycling tests, there were indications of differences in the predominant degradation mechanism between the stacked cells and the other two cell formats. The stacked cells showed faster resistance increases, whereas the coin cells showed faster capacity loss. The difference in degradation mechanism can be linked to the different thermal and mechanical environments in the three cell formats. The correlation in the electrochemical performance between coin cells, single layer pouch cells, and stacked pouch cells shows that developments within a single cell format are likely to lead to improvements across all cell formats.

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“…showed by simulations with and without a coupled thermal model (i.e., with and without heating due to the charging current) that the anode potential is shifted to higher values. [ 103 ] Therefore, larger cells, which usually show a stronger heating due to current flow, [ 166,182 ] are likely to show a lower tendency to lithium metal deposition compared to smaller cells.…”

Section: Anodementioning

confidence: 99%

Fast Charging of Lithium‐Ion Batteries: A Review of Materials Aspects

Weiß

Rueß

Kasnatscheew

et al. 2021

Advanced Energy Materials

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Fast charging is considered to be a key requirement for widespread economic success of electric vehicles. Current lithium‐ion batteries (LIBs) offer high energy density enabling sufficient driving range, but take considerably longer to recharge than traditional vehicles. Multiple properties of the applied anode, cathode, and electrolyte materials influence the fast‐charging ability of a battery cell. In this review, the physicochemical basics of different material combinations are considered in detail, identifying the transport of lithium inside the electrodes as the crucial rate‐limiting steps for fast‐charging. Lithium diffusion within the active materials inherently slows down the charging process and causes high overpotentials. In addition, concentration polarization by slow lithium‐ion transport within the electrolyte phase in the porous electrodes also limits the charging rate. Both kinetic effects are responsible for lithium plating observed on graphite anodes. Conclusions drawn from potential and concentration profiles within LIB cells are complemented by extensive literature surveys on anode, cathode, and electrolyte materials—including solid‐state batteries. The advantages and disadvantages of typical LIB materials are analyzed, resulting in suggestions for optimum properties on the material and electrode level for fast‐charging applications. Finally, limitations on the cell level are discussed briefly as well.

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18650 vs. 21700 Li-ion cells – A direct comparison of electrochemical, thermal, and geometrical properties

Cited by 98 publications

References 35 publications

Increase of Cycling Stability in Pilot-Scale 21700 Format Li-Ion Cells by Foil Tab Design

Increase of Cycling Stability in Pilot-Scale 21700 Format Li-Ion Cells by Foil Tab Design

A Comparison of Lithium-Ion Cell Performance across Three Different Cell Formats

Fast Charging of Lithium‐Ion Batteries: A Review of Materials Aspects

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