NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. A Three-Dimensional Thermal-Electrochemical Coupled Model for Spirally Wound Large-Format Lithium-Ion Batteries Kyu-Jin Lee*, Kandler Smith, Gi-Heon Kim NREL/PR-5400-51151 Space Power Workshop April 18, 2011 Los Angeles, CA This research activity is funded by the US Department of Energy (Dave Howell)
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A Three-Dimensional Thermal-Electrochemical Coupled Model ... · Porous Electrode Model of Li -ion Battery • Pioneered by Newman group (Doyle, Fuller, and Newman 1993) • Captures
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NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
A Three-Dimensional Thermal-Electrochemical Coupled Model for Spirally Wound Large-Format
• Introduces separate computational domains for corresponding length scale physics
• Decouples geometry between the domains• Has independent coordinate systems for each domain• Uses two-way coupling of solution variables using multi-scale model
Large Cell Design can Lead to Large Temperature Difference
• Anisotropic thermal conductivity of electrodes coated on current collectors
Negative current collector
Positive current collector
SeparatorAnode electrode
Cathode electrode
Kin-plane 10-100W/mK
Kthrough-plane ~1W/mK
Prismatic cell Cylindrical cell
• Stacked electrodes • Thin and wide shape helps thermal
uniformity
Kthrough-plane
Kin-plane
Kthrough-plane
Kin-plane
Kin-plane
• Wound electrodes • Center region of cell heats up easily
due to the poor radial thermal conductivity
Innovation for Our Energy Future9
Prismatic cell Cylindrical cell
• Large number of small metal current collectors
• Electric current flows through small distance
• A pair of long continuous metal current collectors
• Electric current flows through long distance.• Tab design can critically impact on cell
performance
Example:Prismatic cell: 200 mm x 150 mm x 7 mmCylindrical cell: radius: 25.85 mm height: 100 mm Thickness of an electrode pair: 300 µm Length of current collectors: ~ 7 m
tab
Cell volume: 0.21 mL
Current
Large Cell Design can Lead to Large Electric Potential Difference
Unit structure: Double-paired electrodes on single-paired current collectors
Negative current collector
Positive current collectorSeparator
Winding: Alternating radial placement of double-paired electrodes
Two electrode pairs are formed when the unit structure is wound
Double-sided anode electrode
Double-sided cathode electrode
Spirally Wound Cell Model
Outer electrode
pair
Inner electrode
pair
Outer electrode
pair
Two points with a distance of a winding cycle of outer electrode pair are matched in the wound structure
Innovation for Our Energy Future15
Spiral Cell Structures: Alternatively layered jelly roll
Positive current collector
Negative current collector
Anode electrodeSeparatorCathode electrode
Outer electrode pairInner electrode pair
A current collector has two electrode pairs in both sides
Innovation for Our Energy Future16
Spiral Cell Structures:
φ-i
φ-i+1
φ-i-1
φ+i
φ+i+1jLi,i
out
i+i+
i-i-
i-
Non-uniform potential along the current collectors occurs from electric current in the winding direction
Non-uniform electrical potential along current collectorsNon-uniform charge transfer reaction across electrodes
Electrical potential fieldsand charge transfer reaction
Innovation for Our Energy Future17
Modeling Case Diameter 40 mm, inner diameter 8 mm, height 100 mm form factor Positive tabs on the top side, negative tabs on the bottom side 10-Ah capacity
5C constant current dischargeSOCini = 90%Natural convection:
5 tabs in each current collector 5C discharge for 5 min
Inner electrode pair
Outer electrode pair
Positive current collector
Negative current collector
0 2 4 6 83
3.2
3.4
3.6
3.8
Time [min]
V out [V
]
Topview
Bottomview
Current mainly flows in the winding direction
High generation rate of transfer current near tabs
Innovation for Our Energy Future
0 2 4 6 825
30
35
40
45
50
Time [min]
Tem
pera
ture
[o C]
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
0.3
0.3
19
State of Charge
TemperatureX [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80
0.05
0.1
0.32
0.34
Modeling ResultsInner electrode pair
Outer electrode pair
Radial heat transfer from tabs Temperature difference is relatively
small
More usage of electrode near tabs
Innovation for Our Energy Future20
Modeling Results: Parametric Study
SOCini = 90%
2 tabs
10 tabs
continuous tab
5 tabs
Different tab numbers (2, 5, 10 and continuous tab) on cell performance 10-Ah capacity, 5C discharge
Output voltage
10 tabs5 tabs2 tabs
2-D modelContinuous
tab
Innovation for Our Energy Future21
Modeling Results:
Temperature 2 tabs5 tabs
10 tabs
2-D model
Continuous tab
Natural convection:hinf = 5 W/m2K
Tamb = 25°C Tini = 25°C
Temperature
Parametric Study
Innovation for Our Energy Future22
Generated Heat
2 tabs5 tabs
10 tabs
2-D mode
Continuous tab
Natural convection:hinf = 5 W/m2K
Tamb = 25°C Tini = 25°C
Modeling Results: Parametric Study
Innovation for Our Energy Future23
High rate of discharge with a moderate heat transfer condition Heat generation dominates temperature distribution in the system
2 tabs5 tabs
10 tabsContinuous
tab
Rejected Heat
Modeling Results: Parametric Study
Innovation for Our Energy Future24
Electrochemical reaction rate comparison
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
i” [A/m2]
2 tabs
5 tabs
Continuous tab
10 tabs
in the inner electrode pair at 5 min
03
56
89
30
120
130
122
121
124
129
128
127
126
125
123
Δi”/ i”avga
32.2%
6.6%
2.2%
0.2%
Modeling Results: Parametric Study
Innovation for Our Energy Future
-0.4
-0.3
-0.2
-0.1
00.1
0.20.3
0.4
25
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1
X [m]
Y [m
]
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.05
0.1T-Tavg [°C]
Temperature deviation comparison
0.19°C
0.37°C
0.78°C
3.25°C
2 tabs
5 tabs
Continuous tab
10 tabs
ΔTat 5 min
-0.4
0.1
-0.3
-0.2
0
-0.1
0.2
0.3
0.4
Modeling Results: Parametric Study
Innovation for Our Energy Future
Conclusions
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• Used Multi-Scale Multi-Dimensional model to evaluate large-format cell designs by integrating micro-scale electrochemical processes and macro-scale heat and electrical current transport.
• Spatial non-uniformity of battery physics, which becomes significant in large batteries, requires 3 dimensional model.
• Developed macro-scale domain model resolved spirally wound structures of lithium-ion batteries.
• Modeled effects of tab configurations and the double-sided electrode structure.
• Increasing the number of tabs in spiral-wound cells would be preferable to manage internal heat and electron current transport, and to achieve uniform electrochemical kinetics.
• The spiral-wound cell model provides quantitative information regarding optimization of cell design including tab location and number.
Innovation for Our Energy Future
US. Department of Energy, Vehicle Technology ProgramDave Howell, Hybrid Electric Systems Team LeaderBrian Cunningham, CAEBAT Coordinator
National Renewable Energy LaboratoryAhmad Pesaran, Energy Storage Team Leader