Challenges of high Quality and high Performance Cell...
Transcript of Challenges of high Quality and high Performance Cell...
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KIT – The Research University in the Helmholtz Association
wbk Institute of Production Science
www.wbk.kit.edu
Challenges of high Quality and high Performance Cell Stacking
Prof. Dr.-Ing. Jürgen Fleischer
Mainz, 2017/01/31
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Slide 22017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Process Chain for the Li-Ion Cell Production
Introduction
Mixing and Coating Calendering Stacking Contacting Diverters Filling and Sealing Formation
High processing speed to ensure economic efficiency
High accuracy to fulfill cell performance, lifetime and
safety requirements
Optimization of handling processes to reduce
unproductive idle times
Prevention of mechanical stresses to the sensitive
electrodes and separator
Objectives related to Stacking
Source: KIT
Especially stacking processes have long cycle-times
and are therefore cost drivers [1]
Today´s stacking processes are often sequential
and inefficient [2]
Handling of thin layers (electrode and separator)
is a highly challenging task [3]
Know-how about stacking processes is pre-dominantly
located in the Asian region [4]
Engineering Challenges related to Stacking
[1] Schröder, R.; Aydemir, M.; Glodde, A.; Seliger, G. (2016): Design and Verificationof an Innovative Handling System for Electrodesin Manufacturing Lithium-ion Battery Cells. In: ProcediaCIRP 50, S. 641–646.
[2] Glodde, A.; Aydemir, M.; Schröder, R.; Seliger, G. (2016): Produktivitätsgesteigerte Zellverbundherstellung*. Kontinuierliche Verfahrensführung zur Herstellung von z-gefalteten Lithium-Ionen-Batteriezellen. In: wt-online, S. 583–587.
[3] Kampker, A.; Kampker, Achim (2014): Elektromobilproduktion. Berlin: Springer Vieweg.[4] Schmitt, J.; Raatz, A.; Dietrich, F.; Dröder, K.; Hesselbach, J. (2014): Processand performance optimization by selective assembly of battery electrodes. In: CIRP Annals- Manufacturing Technology 63 (1), S. 9–12.
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Round Winding
State of the Art
Process (continuous)
Short processing times
No alignment of individual sheets
Continuous process allows single acceleration and
deceleration sequence
Suitable for high production volumes
Long-term production experience
Advantages
Mechanical stress due to small bending radii in the
cell’s center
Unsuitable for processing thick electrodes (bending
radii)
Disadvantages
Double-sided coated electrodes
and separator as input materials
Electrodes wound up together
with separator around mandrel
Round cell after
winding
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Prismatic Winding
State of the Art
Process (continuous)
Mechanical stress due to small bending radii on
compound sides
Mechanical stress due to compression
Unsuitable for processing thick electrodes (bending
radii)
Disadvantages
Short processing times
No alignment of individual sheets
Continuous process allows single acceleration and
deceleration sequence
Suitable for high volume production
Advantages
Electrodes wound up together
with separator around flat mandrel
After winding mandrel is extracted,
“Jelly Roll” is compressed Double-sided coated electrodes
and separator as input materials
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Slide 52017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Single Sheet Stacking
State of the Art
Process (discontinuous)
Long processing times, e.g. through the need for vision
systems and robots for stack formation
Alignment of individual sheets necessary
Cutting burrs propose risk for separator penetration
Particle contamination by laser or die-cutting requires
subsequent cleaning
Disadvantages
No mechanical stress due to bending radii
Suitable for the processing of thick electrodes
High volumetric energy density
Advantages
Electrodes separated via laser or die-cutting,
separator cut via laser or cutting-blade
Single sheets stacked
alternating
Double-sided coated electrodes
and separator as input materials
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Z-Folding (discontinuous)
State of the Art
Process (discontinuous)
Long processing times, e.g. through the need for vision
systems and robots for stack formation
Alignment of individual sheets necessary
Similar disadvantages with respect to contamination
and cutting burrs as for Single Sheet Stacking
Disadvantages
No mechanical stress due to bending radii
Suitable for the processing of thick electrodes
High volumetric energy density
Improved cell-performance due to larger surface area
(better cooling)
Advantages
Electrodes separated via
laser or die-cuttingSingle electrode sheets are
folded into continuous separator
Double-sided coated electrodes
and separator as input materials
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Slide 72017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Challenges
Cell Stacking
Reduction of the cycle time is needed
Minimization of individual steps
Increase of process speed
High process stability (Cp, Cpk)
Process Performance
High accuracy is needed
High cutting edge quality is required
To prevent contamination sub-sequent cleaning is most
likely needed
No cross-contamination between the anode and
cathode
No deformation or damage to electrodes and separator
Process Quality
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Addressing Challenges with current Technology
Cell Stacking
Process-
Performance
Process-
Quality
Cell cycle time [s]: ~ 120 [1] *
Cell cycle time [s]: ~ 81-83 [1] *
Cell cycle time [s]: ~ 30-36 [1] *
* Reference 50 Ah Pouch-Cell; ** Refers to the condition of the electrode
Small loose particles **(e.g. from separation process)
[1] Schröder, R.; Aydemir, M.; Glodde, A.; Seliger, G. (2016): Design and Verification of an Innovative Handling System for Electrodesin Manufacturing Lithium-ion Battery Cells. In: Procedia CIRP 50, S. 641–646.
[5] Schilling, A.; Schmitt, J.; Dietrich, F.; Dröder, K. (2016): Analyzing Bending Stresses on Lithium-Ion Battery Cathodesinduced by the Assembly Process. In: Energy Technol. 4 (12), S. 1502–1508.
Large loose particles ** (e.g. through delamination [10])
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Requirements
High cutting edge quality
with respect to electrodes
and separator
High positioning
accuracy
High production speed
(
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Cut & Place - Machine Assembly
Single Sheet Stacking
Cutting tool with integrated handling system
Fixation of the electrode’s orientation while cutting
Direct placement of the fixed electrode onto the
cell-stack
Approach Single Sheet Stacking Cutting die with integrated Gripper
Defined electrode position
The electrode’s position is defined by the
cutting die, thus no subsequent detection
through vision systems is needed
The electrode’s orientation is kept through
the integrated handling system, wherefore
no subsequent positioning is necessary
Very high accuracy due to only one degree of
freedom and direct placement on the cell stack
Main Advantages
Source: KIT
Guide barsDie cutter cylinder
Vacuum ejector
Electrode web
Vacuum gripper
Die cutting punch
Tool aperture
Source: PCO [8]
Source: Festo [9]
[7] Baumeister, M.; Fleischer, J. (2014): Integrated cut and place module for high productive manufacturing of lithium-ion cells. In: CIRP Annals - Manufacturing Technology 63 (1), S. 5-8.
[8] https://w ww.pco.de/sensitive-cameras/pcopixelf ly-usb/
[9] https://w ww.festo.com.cn/rep/de_de/assets/EXPT_9747mk_1_710px.jpg
Source: Baumeister [7]
Source: KIT
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Cut & Place - Video
Single Sheet Stacking
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Cut & Place - Meeting Target System Requirements
Single Sheet Stacking
Repeatability during positioning
Source: Baumeister [2]
[7] Baumeister, M.; Fleischer, J. (2014): Integrated cut and place module for high productive manufacturing of lithium-ion cells. In: CIRP Annals - Manufacturing Technology 63 (1), S. 5-8.
Requirements
High cutting edge quality with
respect to electrodes
and separator
High positioning
accuracy
The tool’s cutting gap measures
merely 3 µm, resulting in a high
cutting edge quality and no
observed particle accumulations
[2]
Deviation between gripper and
ideal position ≤ 8 µm for
electrode depositing [2]
High production speed
(
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Cut & Place - Conclusion
Single Sheet Stacking
Only one degree of freedom
Very high stacking-accuracy
Reduced risk for lithium-plating
High cutting edge quality
No subsequent cleaning
No particle accumulation
Contamination largely eliminated
Cross contamination between modules was not further
examined
No deformation /damages to electrodes has been
observed
Mechanical cutting
minimal heat input
Process Quality
High stacking speeds realizable
(not verified yet)
Fast and reliable separation of electrodes
No subsequent orientation
Unproductive idle times reduced
To make a statement about the adaptability and
scalability of the proposed concept further
assessments are necessary
Process Performance
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Slide 142017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Unsolved Challenges in Single Sheet Stacking
Outlook
Single Sheet Stacking is still comparatively slow
The space between modules (electrodes
and separator) leaves room for minimization
The ball-screw-drive is limiting the
demonstrator’s operational speed
Handling and cutting the separator is
difficult due to its limpness
The cell stack needs to be build up sheet-
per-sheet (sequentially)
Statistical coverage for the Cut & Place approach
needs to be performed
Relationships between process parameters have
not been sufficiently investigated yet
High speed stacking
Reduction of the space between modules
Using a faster type of drive between
modules, e.g. linear motor
High process stability
Handling new emerging materials
Electrodes of various thicknesses
Very thin separators
Cost reduction
Modularization
Flexibility
Present Vision
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Slide 152017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Helix - Approach
New Approaches
Continuous cell assembly for flat Lithium-Ion batteries
4 continuous material lines
2 x separator coil
1 x anode coil: intermitted double-sided coated
1 x cathode coil: intermitted single-sided coated
Zigzag folding in the intermittent gap
Approach aims at using advantages from continuous and
discontinuous manufacturing processes
Approach Continuous Material Feed
1
2
3
Source: KIT
No tight bending radii
No contamination through particles
Higher energy density compared to Z-folding
Main Advantages
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© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Helix - Meeting Target System Requirements
New Approaches
Requirements
No mechanical damage to
electrodes and separator
No cross-contamination
between electrodes
Material is folded in the intermittent gap,
wherefore a damage to the electrode’s
coating can be avoided
Anode is surrounded by the separator
during processing, wherefore no anode
material can contaminate the cathode
No foreign particles
between layers
High material
utilization
Reduced risk for foreign particles between
layers due to the absence of cutting
processes
No cutting waste since the cell stack is
created by folding the electrodes and
separator
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Slide 172017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Summary
Current technologies for battery manufacturing have been introduced
Main challenges with respect to quality and process performance were outlined
Based on these challenges, a Target System was defined to address current challenges
Two new approaches, which have been developed at the wbk – Institute for Production Science, were introduced and
their impact on current challenges with respect to quantity and performance was explained
Lastly, unsolved challenges which need to be addressed in future research were discussed
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Slide 182017/01/31
© wbk Institute of Production ScienceProf. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze
Thank you for listening!
Prof. Dr.-Ing. Jürgen Fleischer
Kaiserstr. 12, 76131 Karlsruhe
Tel.: +49 721 608 44009
www.wbk.kit.edu