Mikrostruktursimulation der mechanischen Deformation von ...
Jelly Roll Deformation as a Thermo-Mechanical Ageing ... · high rate cycling showing no jelly roll...
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Jelly Roll Deformation as a Thermo-Mechanical Ageing Mechanism in Lithium- Ion-Batteries Kontakt: [email protected] Motivation Experimental S. Gorse 1 , T. Waldmann 2 , T. Samtleben 1,3 , G. Schneider 1 , M. Wohlfahrt-Mehrens 2 , V. Knoblauch 1 Results 1 Hochschule Aalen 2 ZSW Ulm 3 Matworks GmbH Conclusions Acknowledgements To gain a better understanding of the mechanisms that determine the lifetime of Li-ion-cells, macro- and microstructural information is needed. X-ray computed tomography (CT) is an excellent non- destructive method to monitor the interior of 18650 type cells. In the present study, commercially available cells have been subjected to different aging procedures while the jelly roll deformation was monitored and investigated post mortem by SEM-analysis. Additionally, the influence of a centre pin was analysed by comparing three different types of cells without centre pin and one cell with centre pin. Information: www.htw-aalen.de/materialforschung www.zsw-bw.de CT measurements show strong buckling of the inner part of the jelly rolls for the all 18650 cells without centre pin after cycling at discharge rates in the range of 3.6- 16.6C. Most likely, the buckling is induced by thermo-mechanical stresses that arise during high-rate cycling. The jelly roll buckling can be significantly reduced by reducing the C-rates down to 1C. Cycling tests with cells including a centre pin indicate that the deformation may be suppressed by the centre pin that fills the hole of the jelly roll in cylindrical cells. We would like to thank Robert Bosch GmbH for providing the cells within the common research project. This work, based on the project “ReLion”, was funded by the federal ministry of education and research under grant number 03X4619B. The responsibility for the contents of this publication lies with the authors. Type A Type B Type C Activmaterial cathode LiMn 2 O 4 Li(Mn 0,3 Ni 0,5 Co 0,2 )O 2 Li(Mn 0,33 Ni 0,33 Co 0,33 )O 2 / LiMn 2 O 4 Typical capacity 1,2 Ah 2,2 Ah 1,5 Ah float storage U=4.0V, T=70°C U=4.0V, T=70°C U=4.0V, T=70°C low rate cycling 0.9C charge, 1C discharge, T=70°C 1C charge, 1C discharge, T=25°C 1C charge, 1C discharge, T=60°C high-rate cycling 0.9C charge, 3.6C discharge, T=25°C 4.33C charge, 16C discharge, T=50°C 1C charge, 1C discharge, T=60°C Aging conditions a) Axial CT scan of a type C cell without centre pin at mid-height of the 18650 cylinders; b), c) and d) SEM images of the cross sections shows contact loss in the anode and cathode active material. Type A Type B Type C float storage low-rate cycling high-rate cycling Axial (a) and tangential (b) CT scans of a type C cell with a centre pin after high rate cycling showing no jelly roll deformation Comparison: Axial CT scans of cell type A, B and C without centre pin at different aging conditions. Especially during high-rate cycling, all cell types show jelly roll deformation. In-operando temperature measurement of an un-aged cell type C during CC discharge of 16C (after CC charge to 4.2V). It shows a significant temperature difference between the cell surface and inside the jelly roll. Sensor positions Cell types
Transcript of Jelly Roll Deformation as a Thermo-Mechanical Ageing ... · high rate cycling showing no jelly roll...
Jelly Roll Deformation as a Thermo-Mechanical Ageing Mechanism in Lithium-Ion-Batteries
Kontakt: [email protected]
Motivation Experimental
S. Gorse1, T. Waldmann2, T. Samtleben1,3, G. Schneider1, M. Wohlfahrt-Mehrens2, V. Knoblauch1
Results
1 Hochschule Aalen 2 ZSW Ulm 3 Matworks GmbH
Conclusions Acknowledgements
To gain a better understanding of themechanisms that determine the lifetime ofLi-ion-cells, macro- and microstructuralinformation is needed. X-ray computedtomography (CT) is an excellent non-destructive method to monitor the interiorof 18650 type cells. In the present study,commercially available cells have beensubjected to different aging procedureswhile the jelly roll deformation wasmonitored and investigated post mortem bySEM-analysis. Additionally, the influence ofa centre pin was analysed by comparingthree different types of cells without centrepin and one cell with centre pin.
Information: www.htw-aalen.de/materialforschung www.zsw-bw.de
CT measurements show strong buckling of the inner part of the jelly rolls for the all18650 cells without centre pin after cycling at discharge rates in the range of 3.6-16.6C. Most likely, the buckling is induced by thermo-mechanical stresses that ariseduring high-rate cycling. The jelly roll buckling can be significantly reduced byreducing the C-rates down to 1C. Cycling tests with cells including a centre pinindicate that the deformation may be suppressed by the centre pin that fills the holeof the jelly roll in cylindrical cells.
We would like to thank Robert Bosch GmbHfor providing the cells within the common research project.
This work, based on the project “ReLion”, was funded by the federal ministry of education and research under grant number 03X4619B. The responsibility for the contents of this publication lies with the authors.
Type A Type B Type C
Activmaterialcathode LiMn2O4 Li(Mn0,3Ni0,5Co0,2)O2
Li(Mn0,33Ni0,33Co0,33)O2/LiMn2O4
Typical capacity 1,2 Ah 2,2 Ah 1,5 Ah
float storage U=4.0V,
T=70°C
U=4.0V,
T=70°C
U=4.0V, T=70°C
low rate cycling 0.9C charge, 1C discharge,
T=70°C
1C charge, 1C discharge,
T=25°C
1C charge, 1C discharge,
T=60°C
high-rate cycling 0.9C charge, 3.6C discharge,
T=25°C
4.33C charge, 16C discharge,
T=50°C
1C charge, 1C discharge,
T=60°CAg
ing
co
nd
itio
ns
a) Axial CT scan of a type C cell without centre pin at mid-height of the 18650cylinders; b), c) and d) SEM images of the cross sections shows contact loss inthe anode and cathode active material.
Type A
Type B
Type C
float storage low-rate cycling high-rate cycling
Axial (a) and tangential (b) CT scans of a type C cell with a centre pin afterhigh rate cycling showing no jelly roll deformation
Comparison: Axial CT scans of cell type A, B and C without centre pin atdifferent aging conditions. Especially during high-rate cycling, all celltypes show jelly roll deformation.
In-operando temperature measurement of an un-aged cell type C during CCdischarge of 16C (after CC charge to 4.2V). It shows a significant temperaturedifference between the cell surface and inside the jelly roll.
Sensor positions
Cel
l typ
es
