14
Meng Xiao, [email protected] 1 Copying this presentation is strictly forbidden. Thermal Modeling and Analysis of a Pouch Type Li-Polymer Battery Meng Xiao, Auburn University
Meng Xiao, [email protected] 1 Copying this presentation is strictly forbidden.
Thermal Modeling and Analysis of a Pouch Type
Li-Polymer Battery
Meng Xiao, Auburn University
Meng Xiao, [email protected] 2 Copying this presentation is strictly forbidden.
Overview
• Literature review
• Heat sources analysis
• Heat generation measurement using infrared camera
• Heat generation measurement using calorimeter
• Simulation using electrochemical thermal model
Meng Xiao, [email protected] 3 Copying this presentation is strictly forbidden.
Literature review
• In 2003, K. Thomas and J. Newman proposed heat of mixing in Li-ion battery
electrodes. [1]
• In 2008, X. Zhang etc. in U of Michigan claim the heat of mixing is negligible
compare to other heat source terms. [2]
[1] K.Thomas, J. Newman, J. Power Sources, Vol. 119-121, 2003, pp. 844-849
[2] X. Zhang etc. J. Electrochemical Soc. Vol.155(7) , 2008, pp. A542-A552
* Data provided by 3M company, 2011
-4-2024
Heat generation test of a coin cell *
Curr
ent, A
3.6
3.8
Voltage, V
1000 2000 3000 4000 5000 6000 70000
0.2
Time, s
Heat flow
, m
W
• Researcher in 3M company
observed heat generation rate
decayed slowly after current
interruption, (lasts 1000s) in coin
cell.
Meng Xiao, [email protected] 4 Copying this presentation is strictly forbidden.
Heat source terms
• Reversible heat generation: Change of entropy
• Irreversible heat generation: Joule heating
in electrode
in electrolyte
by overpotential
in current collector
• Total sum of the heat generation: qg=qrev+qirr=qrev+qs+qe+qact+qcc
T
ETjq Li
rev
2
lq seff
s
Generate heat qrev
Generate heat qirr
Discharge
qrev Generate
heat qirr
Charge
Absorb heat
ll
c
lq eeeff
Deeff
e
ln2
Li
act jq 22
yxq cc
cccc
cccc
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Interpretation of the Heat of mixing
• Electrode with different
stoichiometry number has
large chemical potential
difference
• Lithium ions in electrodes
are not uniform distributed
at charging or discharging
• The process of lithium ion
moving from high potential
part to low potential part
result in heat of mixing
Concentration of Li ion in solid @ 5C discharge
00.5
1
0
0.5
1
0.4
0.6
0.8
r (radius)
15s
l (thickness)
Cs/C
s.m
ax
00.5
1
0
0.5
1
0.4
0.6
0.8
r (radius)
100s
l (thickness)
Cs/C
s.m
ax
00.5
1
0
0.5
1
0
0.5
1
r (radius)
200s
l (thickness)
Cs/C
s.m
ax
00.5
1
0
0.5
1
0
0.5
1
r (radius)
600s
l (thickness)
Cs/C
s.m
ax
0 0.2 0.4 0.6 0.8 1
Sep
arat
or
Curr
ent
coll
ecto
r (C
u)
Curr
ent
coll
ecto
r (A
l)
Positive
electrode
area
Negative
electrode
area
L
Electrode
particle
Ion flux
Different
chemical
potential
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Infrared camera approach
• Anti-glare spray on the battery surface
• FLIR SC655 infrared camera Frame rate: 50 Hz
Resolution: 640*480 pixels
Thermal sensitivity - <0.05°C @30°C/50mK
Focus distance – 24.6 mm
Object temperature range – -20°C to 150°C
• Multiple digital filters employed to reduce noise
• Differentiate temperature to calculate heat generation
Meng Xiao, [email protected] 7 Copying this presentation is strictly forbidden.
IR camera approach
0 50 100 150-20
0
20
40
60
80
100
Time, sec
He
at
Ge
ne
ratio
n R
ate
, W
att
simulation
experiment
heat generation comparison of 110A cycle test
7C charge
rest
7C discharge
rest
• Temperature differentiate method based on the temperature profile measured
from IR camera
• 7C cycle because of noises
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Design of Calorimeter
Thermal
couples
TEMs
Battery
TEM controller Tref
battery
temperature
Qestimate
Heat pump
estimator Load profile
• Battery
LiMn2O4/Carbon pouch type power cell
15.7Ah, 15cm*20cm*5mm
Voltage range 2.5V~4.15V
• Thermal-electric module (TEM) * 2
24V, 160W
• Labview implementation
Measurement of temperature at center and
terminals
PI controller
Overpotential heat generation estimation
Heat transfer from terminal tabs estimated
Goal: fast response and small error
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1 1.5 2 2.5 3 3.5 4
x 10-3
0
0.5
1
1.5
2
2.5
3
3.5x 10
-3 Battery EIS
Calorimeter calibration – AC current
1.9e-3 Ohm @ 1Hz
• Battery is pure resistive if applied 1Hz AC current.
• Joule heating dominants the overall heat generation at this frequency
• Impedance at certain frequency is independent to current amplitude
-100 -50 0 50 100
3.3
3.4
3.5
3.6
3.7
Battery current, A
Term
inal voltage, V
Battery response to 1Hz AC current
73.9A
54.4A
40.0A
23.3A
8.13A
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Calorimeter calibration – AC current
• PI controller
• Apply AC current to the battery
• Temperature control error < 0.02 ºC
• Heat transfer through terminal tab
0 500 1000 1500 2000 2500-150
-100
-50
0
50
100
150
Time, s
Battery
curr
ent, A
Battery IRMS
=68.5A, 1Hz (Ip-p
=193.7A)
0 500 1000 1500 2000 250022
22.2
22.4
22.6
22.8
23
Time, s
Battery
tem
pera
ture
, oC
Battery IRMS
=68.5A, 1Hz (Ip-p
=193.7A)
0 2 4 6 8 100
0.05
0.1
0.15
0.2
Battery heat generation, W
TE
M c
urr
ent, A
• The heat pump coefficient = 52.6W/A
• Heat transfer through each terminal tab = 0.315W/K
• The clear step of TEM current is observed
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5C discharge (consider TEM effect)
400 600 800 1000 1200 1400
0
20
40
60
80
Time, s
Heat genera
tion ,W
5.1C (80A) discharge
Measured Qg
Battery QOP
400 600 800 1000 1200 1400
0
20
40
60
80
Time, s
Heat genera
tion ,W
5.1C (80A) charge
Measured Qg
Battery QOP
•Heat generation rate is almost same amount as overpotential heating
with slightly phase delay
• In 5C charge and discharge at room temperature, heat generation after
current interrupt will quickly decay to zero within no more than 60s
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Model setup for pouch type cell
• Micro cell has current collector / separator / electrode layers
• Electrode is mixture of electrode particles and electrolyte
• Chemical reaction occur at surface of particles
• Lithium ion de-intercalate from one electrode, travel through electrolyte and intecalate
to the other electrode
• A pouch type cell is assumed to consist of microcells that have multiple layers in the L
direction, so that the microcell is simplified with one dimensinal model.
• ce
• Φe
• Φs
• ηSEI
• cs
• T
Sep
arat
or
LixC6 LiyMO2
Curr
ent
coll
ecto
r (C
u)
Curr
ent
coll
ecto
r (A
l)
Electrolyte
Positive
electrode
area
Negative
electrode
area
Electrode
particle
L
X
Y
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Dynamic modeling
Micro cell model Micro cell model
•Energy conservation
•Heat transfer
•Charge conservation
Temperature
distribution
Parameters:
•Battery geometry
•Maximum capacity
•Concentration
•Activity coefficient
•Diffusion
coefficient
•Change of enthalpy
•Conductivity
etc.
•Cell voltage
•Temp. distribution
•SOC
•Overpotentials
•Reaction rate
•Concentration
•Efficiency
•Butler-Volmer
Mass balance
•In electrolyte
•In solid
Reaction rate
Current
Overpotential
Concentration
Nernst
equ.
Standard
potential
Micro cell model
Initial conditions:
•Initial SOC
•Load profile
•Initial temperature
distribution
•Ambient
temperature
Single cell model
Potential
distribution
Heat source
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Simulation result
400 600 800 1000 1200 1400
0
20
40
60
80
Time, s
Heat genera
tion, W
80A discharge validation
simulation
experiment
400 600 800 1000 1200 1400
0
20
40
60
80
Time, s
Heat genera
tion, W
80A charge validation
simulation
experiment
Both simulation and experiment result show the heat generation after current
interrupt is very small and rapid decay to zero at the given LIPB cells.
