Evaluation Study for Large Prismatic Lithium-Ion Cell ... - NREL

Evaluation Study for Large Prismatic
Lithium-Ion Cell Designs Using
Multi-Scale Multi-Dimensional Battery Model
Gi-Heon Kim and Kandler Smith
National Renewable Energy Laboratory
Golden, Colorado
NREL/PR-540-46076
This research activity is funded by the U.S. Department of Energy
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.

Batteries for Electrified Vehicles
Electrified drive-train vehicles such as PHEVs and EVs with rangeextenders
are believed to be near-term technologies that are
• displacing significant petroleum use in the transportation sector
• diversifying energy sources for mobility
Advances in batteries are critical to realize green mobility technologies
DOE’s Energy Storage System Performance Targets for PHEVs
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Batteries for Electrified Vehicles
Electrified drive-train vehicles such as PHEVs and EVs with rangeextenders
are believed to be near-term technologies that are
• displacing significant petroleum use in the transportation sector
• diversifying energy sources for mobility
Advances in batteries are critical to realize green mobility technologies
DOE’s Energy Storage System Performance Targets for PHEVs
Performance
Life
Cost
Safety
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Multi-Scale Physics in Li-Ion Battery
Requirements & Resolutions
“Requirements” are usually defined
in a macroscale domain and terms
Performance
Life
Cost
Safety
• Wide range of length and time scale physics
• Design improvements required at different scales
• Need for better understanding of interaction among different scale physics
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Multi-Physics Interaction
electrochemical
current production
Comparison of two 40 Ah
flat cell designs
2 min 5C discharge
working potential working potential
temperature temperature
electrochemical
current production
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Multi-Physics Interaction
�Larger over-potential
promotes faster discharge
reaction
�Converging current
causes higher potential
drop along the collectors
electrochemical
current production
�High temperature
promotes faster
electrochemical reaction
�Higher localized reaction
causes more heat
generation
Comparison of two 40 Ah
flat cell designs
2 min 5C discharge
working potential working potential
temperature temperature
electrochemical
current production
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Multi-Physics Interaction
�Larger over-potential
promotes faster discharge
reaction
�Converging current
causes higher potential
drop along the collectors
electrochemical
current production
�High temperature
promotes faster
electrochemical reaction
�Higher localized reaction
causes more heat
generation
Comparison of two 40 Ah
flat cell designs
2 min 5C discharge
working potential working potential
soc
temperature temperature
This cell is cycled
more uniformly, can
therefore use less
active material ($)
and has longer life.
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soc
electrochemical
current production

Electrode-Scale Performance Model
Charge Transfer Kinetics at Reaction Sites
Species Conservation
Charge Conservation
( φ − ) −U
η = φ
s
e
• Pioneered by Newman group (Doyle, Fuller,
and Newman 1993)
• Captures lithium diffusion dynamics and charge
transfer kinetics
• Predicts current/voltage response of a battery
• Provides design guide for thermodynamics,
kinetics, and transport across electrodes
Energy Conservation • Difficult to resolve heat and electron current
∂T
ρc
p = ∇ ⋅(
k∇T
)
transport
+ q′
′
∂t
Li ⎛
∂U
eff
eff
eff
q′ ′
⎞
= j ⎜φs
−φ
e −U
+ T ⎟ + σ ∇φs
⋅∇φ
s + κ ∇φe
⋅∇φ
e + κ D ∇lnc
e ⋅∇φ
e
⎝
∂T
⎠
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r

Integrated Model Resolving Different Scale Physics
To expand knowledge of the impacts of designs in different scales,
usages, and management on performance, life, and safety of battery
systems
Li Transport &
Charge Transfer Kinetics
Electron Transport &
Heat Transport
Simply Work?
Extend model domain size up to cell scale to capture macroscopic design
features, while maintaining model resolution to capture Li diffusion dynamics
in electrode level scale ??? � huge computational complexity and cost
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Approach
Multi-Scale Multi-Dimensional (MSMD) Model
Simulation
Domain
= Macro Grid + Micro Grid
(Grid for Sub-grid Model)
• Captures macroscopic electron/heat transports, electrode scale Li
diffusion dynamics/charge transfer kinetics in separate domains
• Physically couple the solution variables defined in each domain using
multi-scale modeling schemes
• Runs in tolerable calculation time, practical for battery and system
engineering design
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X
R
Current Collector (Cu)
Negative
Electrode
x
Separator
Positive
Electrode
Current Collector (Al)

Present Study
“Poorly designed electron and heat transport paths can cause excessive
spatial non-uniformity in battery physics, and then deteriorate the
performance and shorten the life of the battery.”
Fixed Microscopic Designs Macroscopic Features as Design Variables
Objectives
Demonstrate the impact of macroscopic design factors on battery …
• Performance : B2 abs# 252 (Kim & Smith) � This talk
• Life: B2 abs# 255 (Smith & Kim)
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Nominal Design – 10C discharge for 30 sec
� Stacked prismatic design
� 140 x 100 x 15 mm 3 form factor
� Tabs on a same side
� 20 Ah
� PHEV10 application
� 10C constant current discharge
� soc ini = 90%
� Surface and tab cooling
� h inf = 20 W/m 2 K
� T amb = 30 o C
� T ini = 30 o C
3.2
0 5 10 15
t (s)
20 25 30
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(V)
4
3.8
3.6
3.4
V(t)
OCV(t)
evaluated from volumetric
average of composition
15 mm

Electrical Response – 10C Discharge
Current density field at metal collector foils
after 30 sec discharge at mid-plane
Y(mm)
Y(mm)
100
80
60
40
20
0
0 20 40 60
X(mm)
80 100 120 140
100
80
60
40
20
Al foil
Cu foil
0
0 20 40 60
X(mm)
80 100 120 140
Working potential between electrode planes
after 30 sec discharge at mid-plane
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Electrical Response – 10C Discharge
Current density field at metal collector foils
after 30 sec discharge at mid-plane
Y(mm)
Y(mm)
100
80
60
40
20
0
0 20 40 60
X(mm)
80 100 120 140
100
80
60
40
20
Al foil
Cu foil
0
0 20 40 60
X(mm)
80 100 120 140
after 30 sec discharge at mid-plane
3.37
3.36
3.35
3.34
100
Working Potential [V] Working potential between electrode planes
50
Large Overpotential
Y(mm)
0
0
100
50
X(mm)
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… …
3.37
3.365
3.36
3.355
3.35
3.345
3.34

Temperature [ ° C]
36
34
32
30
100
T(t) [ ° C]
Thermal Response – 10C Discharge
Temperature Evolution at Mid-Plane
50
Y(mm)
36
34
32
0
0
Temperature [ ° C]
36
34
32
30
100
100 50
50
X(mm) Y(mm)
0
0
Temperature [ ° C]
avarage temperature
36
34
32
30
100
100 50
50
X(mm) Y(mm)
maximum temperature
minimum temperature
0
0
Temperature [ ° C]
36
34
32
30
100
100 50
50
X(mm) Y(mm)
30
0 5 10 15
t [s]
20 25 30
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0
0
Temperature [ ° C]
36
34
32
30
100
100 50
50
X(mm) Y(mm)
0
0
Temperature [ ° C]
36
34
32
30
100
100 50
50
X(mm) Y(mm)
5s 10s 15s 20s 25s 30s
0
0
100
50
X(mm)
36
34
32
30

35
34
Thermal Response – 10C Discharge
Temperatures after 30 sec discharge
35.9
35.5
34.5
33.6
� T ini =30.0 o C
� T avg=34.3 o C � ∆T=2.3 o C
Z(mm)
Z(mm)
Z(mm)
15
10
5
0
0 20 40
Y(mm)
60 80 100
15
10
5
0
0 20 40
Y(mm)
60 80 100
15
10
5
0
0 20 40
Y(mm)
60 80 100
Y(mm)
Y(mm)
100
80
60
40
20
0
0 20 40 60
X(mm)
80 100 120 140
100
80
60
40
20
mid-plane
surface
0
0 20 40 60
X(mm)
80 100 120 140
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i [A/m 2 ]
soc-soc avg (%)
285
280
275
270
100
0.4
0.2
Electrochemical Response – 10C discharge
50
Y(mm)
0
-0.2
-0.4
100
discharge current density
0
0
soc- soc avg
50
Y(mm)
soc(t) [%]
0 0
90
85
i [A/m 2 ]
100
50
X(mm)
285
280
275
270
100
50
Y(mm)
0
0
i [A/m 2 ]
100
50
X(mm)
285
280
275
270
100
50
Y(mm)
0
0
i [A/m 2 ]
100
50
X(mm)
285
5s 10s 15s 20s 25s 30s
soc-soc avg (%)
100
50
X(mm)
0.4
0.2
0
-0.2
-0.4
100
50
Y(mm)
0
0
soc-soc avg (%)
100
50
X(mm)
0.4
0.2
0
-0.2
-0.4
100
50
Y(mm)
0
0
soc-soc avg (%)
100
50
X(mm)
280
275
270
100
80
0 5 10 15
t [s]
20 25 30
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0.4
0.2
-0.2
-0.4
100
50
Y(mm)
0
50
Y(mm)
0
0
0
0
i [A/m 2 ]
100
50
X(mm)
soc-soc avg (%)
100
50
X(mm)
285
280
275
270
100
0.4
0.2
-0.2
-0.4
100
50
Y(mm)
0
50
Y(mm)
0
0
0
0
i [A/m 2 ]
100
50
X(mm)
soc-soc avg (%)
100
50
X(mm)
285
280
275
270
100
0.4
0.2
-0.2
-0.4
100
50
Y(mm)
0
50
Y(mm)
0
0
avarage soc
0
maximum soc
minimum soc
0
100
50
X(mm)
100
50
X(mm)

Virtual Design Evaluation
Virtual
Vehicle Design
Virtual
Battery Design
Feedback
Embedded
Battery Model
Vehicle Simulator
Multi-Scale
Multi-Dimensional
Li-ion Battery Model
Battery Responses
90
80
70
60
50
40
30
20
10
0
-10
Vehicle Speed
0 100 200 300 400 500 600
800
600
400
200
-200
-400
Time (s)
Vehicle Driving Profile
0
-600
0 10 20 30 40 50 60
Battery Power Profile
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Alternative Cell Designs
Nominal Design
• 140 x 100 x 15 mm 3
• Tabs on a same side
• 20 Ah
Small Capacity
Thin and Wide
Counter Tab
SC
TW
CT
• 3 x (140 x 100 x 5) mm 3
• Same tab design
• 3 x 6.67 Ah
• Same electrode area/stack layer
• 1/3 thickness
• ~ 3x surface area
• 200 x 140 x 7.5 mm 3
• Same tabs
• 20 Ah
• 2x electrode area/stack layer
• 1/2 thickness
• ~ 2x surface area
• 250 x 120 x 7 mm 3
• Wide-counter tab design
• 20 Ah
• ~2x electrode area/stack layer
• ~1/2 thickness
• ~2x surface area
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T(t) [ ° C]
60
55
50
45
40
35
Thermal Behavior Comparison
Battery Power Profile
mid-size sedan PHEV10 US06 drive
800
600
400
200
0
-200
-400
-600
0 10 20 30 40 50 60
3 x
30
0 5 10 15
t [min]
T(t) [ ° C]
60
55
50
45
40
35
30
0 5 10 15
t [min]
• 15-minute drive (CD + CS)
• soc ini = 90%
• Surface and tab cooling
• h inf = 20 W/m 2 K
• T amb = 30 o C
• T ini = 30 o C
SC TW CT
30
0 5 10 15
t [min]
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T(t) [ ° C]
60
55
50
45
40
35

Temperature Imbalance during CD Drive
T avg (t) [ ° C]
∆T(t) [ ° C]
55
50
45
40
35
30
25
0 5 10 15
t [min]
14
12
10
8
6
4
2
0
0 5 10 15
t [min]
Nominal
TW
CT
SC
54
52
50
48
46
44
42
100
80
60
40
20
140
120
100
0
0 20 40 60 80 100 120 140
80
60
40
20
@ t = 6 min
0
0 20 40 60 80 100 120 140 160 180 200
0
0 20 40 60 80 100 120 140
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SC
TW
100
80
60
40
20
250
200
150
100
50
Nominal
CT
0
0 20 40 60 80 100 120

Temperature Imbalance during CS drive
T avg (t) [ ° C]
∆T(t) [ ° C]
55
50
45
40
35
30
25
0 5 10 15
t [min]
14
12
10
8
6
4
2
0
0 5 10 15
t [min]
Nominal
TW
CT
SC
48
46
44
42
40
38
36
100
80
60
40
20
0
0 20 40 60 80 100 120 140
140
120
100
80
60
40
20
@ t=15 min
0
0 20 40 60 80 100 120 140 160 180 200
100
80
60
40
20
0
0 20 40 60 80 100 120 140
250
200
150
100
50
Nominal
0
0 20 40 60 80 100 120
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SC
TW
CT

Ah Throughput Imbalance TW vs CT
Ah/m 2
28
27.5
27
26.5
26
25.5
V ocv [V]
3.9
3.8
3.7
3.6
3.5
3.4
0 5 10 15
t [min]
Y(mm)
140
120
100
80
60
40
20
TW
CT
0
0 20 40 60 80 100
X(mm)
120 140 160 180 200
Y(mm)
250
200
150
100
50
0
0 20 40 60
X(mm)
80 100 120
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TW
CT

Summary
Nonuniform battery physics, which is more probable in large-format
cells, can cause unexpected performance and life degradations in
lithium-ion batteries.
A Multi-Scale Multi-Dimensional model was used for evaluating
large format prismatic automotive cell designs by integrating microscale
electrochemical process and macro-scale transports.
Thin form factor prismatic cell with wide counter tab design would
be preferable to manage cell internal heat and electron current
transport, and consequently to achieve uniform electrochemical
kinetics over a system.
Engineering questions to be addressed in further discussion include …
What is the optimum form-factor and size of a cell?
Where are good locations for tabs or current collectors?
How different are externally proved temperature and electric signals from nonmeasurable
cell internal values?
Where is the effective place for cooling? What should the heat-rejection rate be?
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Acknowledgments
Vehicle Technology Program at DOE
• Dave Howell
NREL Energy Storage Task
• Ahmad Pesaran
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