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Transcript of CESE November 13, 2009 Jai Prakash Center for Electrochemical Science and Engineering Department of...
CESE November 13, 2009November 13, 2009
Jai Prakash
Center for Electrochemical Science and EngineeringCenter for Electrochemical Science and Engineering
Department of Chemical and Biological EngineeringDepartment of Chemical and Biological EngineeringIllinois Institute of TechnologyIllinois Institute of Technology
Electrochemical and thermal Electrochemical and thermal characterization of Li-ion batteriescharacterization of Li-ion batteries
CESE November 13, 2009November 13, 2009
Li-ion cell reactionsLi-ion cell reactions
2 m
MCMB
2 m
MCMB
Oxide
1 m
Metal oxide cathodeMetal oxide cathodeLiMOLiMO22
Graphite anodeGraphite anode
LiP
F6
/EC
,DM
C
High volumetric energy/power densitiesHigh volumetric energy/power densities
CESE November 13, 2009November 13, 2009
Limitations of Li-ion cellsLimitations of Li-ion cells
High power performance High power performance Cell impedance)Cell impedance)
Cycle life Cycle life Cell impedanceCell impedance
Thermal safety Thermal safety Structural stability of delithiated oxideStructural stability of delithiated oxide Cell impedance produces heatCell impedance produces heat
CostCost
CESE November 13, 2009November 13, 2009
Typical Changes in Li-ion Cell EIS with TimeTypical Changes in Li-ion Cell EIS with Time
Impedance rise is associated with interfacial arcImpedance rise is associated with interfacial arc
Most of the impedance is attributed to the positive electrodeMost of the impedance is attributed to the positive electrode
EIS for G2.60C55.A215.33.28.26.G.T.
0
0.005
0.01
0.015
0.02
0.025
0.03
0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04
Zreal, ohms
-Zim
ag,
oh
ms
Characterization t = 0
RPT #1 t = 4 weeks
RPT #2 t = 8 weeks
RPT #3 t = 12 weeks
RPT #4 t = 16 weeks
RPT #5 t = 20 weeks
RPT #6 t = 24 weeks
RPT #7 t = 28 weeks
RPT #8 t = 32 weeks
RPT #9 t = 36 weeks
mid-freq min
high freq min
EIS for G2.60C55.A215.33.28.26.G.T.
0
0.005
0.01
0.015
0.02
0.025
0.03
0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04
Zreal, ohms
-Zim
ag,
oh
ms
Characterization t = 0
RPT #1 t = 4 weeks
RPT #2 t = 8 weeks
RPT #3 t = 12 weeks
RPT #4 t = 16 weeks
RPT #5 t = 20 weeks
RPT #6 t = 24 weeks
RPT #7 t = 28 weeks
RPT #8 t = 32 weeks
RPT #9 t = 36 weeks
mid-freq min
high freq min
CESE November 13, 2009November 13, 2009
(003) reflections are weak or absent (003) reflections are weak or absent in oxide surface layersin oxide surface layers
5 nm Surface Film
~ 5-10 nm
HR-TEM of cycled oxide particlesHR-TEM of cycled oxide particles
LiNiO2-typeLixNi1-xO-type
CESE November 13, 2009November 13, 2009
Electrochemical Model ApproachElectrochemical Model Approach
Porous electrode model
Solid electrolyte interface (SEI) and interfacial oxide film included in the model
Diffusion through the electrolyte, SEI film, interfacial oxide, and bulk oxide considered
Butler-Volmer relation used for electrochemical reaction
AC impedance model constructed for Li-ion cell
CESE November 13, 2009November 13, 2009
Governing equations for the AC impedance modelGoverning equations for the AC impedance model
Linear perturbation Linear perturbation
complex analysiscomplex analysis
0 0 0 )' ( R Ij t j tjc c c c c e c c c e
00
c cc c
dDD D c
dc
1 tanh tanh-
tanh tanh
sbbs ibs
si sisbsbs
si sbs ib
si sisb
D j jdU KK D D DdcZ
z F D j D j jK
D D D
Numerical solution of a set of coupled differential equationsNumerical solution of a set of coupled differential equations
Kinetic impedance and lithium diffusion in active particlesKinetic impedance and lithium diffusion in active particles
2 2
2 2( ) ( )( )m
o a a
m
o oa a a am
nk
c
k FcRT j
F Fk k c
RT RT
Z
CESE November 13, 2009November 13, 2009
Simulation and prediction for the positive electrode Simulation and prediction for the positive electrode
0
5
10
15
20
25
0 5 10 15 20 25
Z' (Real) ohm.cm2
Z"
(Im
) o
hm
.cm
2 simulation
Experimental
0123456
0 4 8 12Z' (Real) ohm.cm2
-Z" (
Im)
oh
m.c
m2
4.00 m1.55 m0.37 m
0123456
0 4 8 12Z' (Real) ohm.cm2
-Z" (
Im)
oh
m.c
m2
4.00 m1.55 m0.37 m
0123456
0 5 10 15
-Z"
(Im
) o
hm
.cm
2
DLi Cathode
3.510-9 cm2/s1.710-9 cm2/s
0123456
0 5 10 15
-Z"
(Im
) o
hm
.cm
2
DLi Cathode
3.510-9 cm2/s1.710-9 cm2/s
0
10
20
30
0 5 10 15 20
-Z"
(Im
) O
hm
.cm2
20 nm oxide layer
10 nm oxide layer
0
10
20
30
0 5 10 15 20
-Z"
(Im
) O
hm
.cm2
20 nm oxide layer
10 nm oxide layer
Oxide layerLi diffusion
Particle size Electrolyte conductivity
CESE November 13, 2009November 13, 2009
Safety Concerns of Li-ion BatteriesSafety Concerns of Li-ion Batteries
• Large-scale batteries for electric and hybrid vehicles
• Thermal runaway
-High power discharge
-Overcharge
-Abusive and cell-shorting conditions
• Heat and pressure build-up within the cell
• Cell fire caused by the flammable electrolyte
CESE November 13, 2009November 13, 2009
Thermal runaway produces fire in Li-ion cellsThermal runaway produces fire in Li-ion cells
Peter Roth (Sandia National Lab)Peter Roth (Sandia National Lab)
18650 Li-ion cell18650 Li-ion cell
CESE November 13, 2009November 13, 2009
Understanding Thermal Runaway in Li-ion Cells: Understanding Thermal Runaway in Li-ion Cells: A Fire TriangleA Fire Triangle
CESE November 13, 2009November 13, 2009
In-situIn-situ studies of thermal effects in Li-ion cells studies of thermal effects in Li-ion cells during normal cycling using IMCduring normal cycling using IMC
Current C/20 C/10 C/5 C/1
Qanode
mJ.cm-2
61 54 27 -74
Qcathode
mJ.cm-2
-84 -93 -110 -214
-30
-20
-10
0
10
20
30
40
50
60
70
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x in LixNi0.8Co0.15Al0.05O2
Hea
t Rat
e,
uW.c
m-2
-30
-20
-10
0
10
20
30
40
50
60
70
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x in LixNi0.8Co0.15Al0.05O2
Hea
t Rat
e,
uW.c
m-2
Charge
Discharge
CESE November 13, 2009November 13, 2009
DSC features of Mag-10 anode at various SOCDSC features of Mag-10 anode at various SOC
-17
-15
-13
-11
-9
-7
-5
-3
-1
1
60 110 160 210 260 310 360
Temperature, oC
No
rma
lize
d H
ea
t R
ate
, W
/g
Li0C6
Li0.18C6
Li0.37C6
Li0.57C6
Li0.7C6
Li0.9C6
SEI dec
ompo
sitio
n
SEI dec
ompo
sitio
n
CESE November 13, 2009November 13, 2009
Enthalpy vs. the amount of intercalated lithium in Enthalpy vs. the amount of intercalated lithium in the secondary SEI film formationthe secondary SEI film formation
-3000
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
x in LixC6
de
lta
_H
, J
/g
1600 J/g for Mag-101600 J/g for Mag-10
The formation of a secondary The formation of a secondary SEI film consumes about 0.37 LiSEI film consumes about 0.37 Li
CESE November 13, 2009November 13, 2009
DSC and XRD of DSC and XRD of LiNi0.8Co0.15Al0.5O2 cathode at various SOC
0
1
2
3
4
5
6
7
8
9
50 100 150 200 250 300 350
Temperature, oC
No
rmal
ize
d H
eat
Flo
w (
exo
up
), W
/g
100%
50%
20%
70%
0%
Peak shift
- 941 J/g
- 730 J/g
- 709 J/g
- 352 J/g
- 150 J/g
H (J/g)
0
1000
2000
3000
4000
5000
55 60 65 70 75Angle, 2
Inte
nsit
y, c
ou
nts
25oC
250oC
225oC
200oC
175oC
150oC
100oC
10
7
01
8
11
0
11
3
CESE November 13, 2009November 13, 2009
Thermal studies of LiThermal studies of Li0.360.36NiNi0.80.8CoCo0.150.15AlAl0.050.05OO22 (CDL) With and (CDL) With and
Without Electrolyte using ARCWithout Electrolyte using ARC
Flash point of EC: 150oC
SHR dramatically increased from 150oC is due to the combustion of the electolyte with released O2 from delithiated cathode
0
50
100
150
200
250
300
0 500 1000 1500 2000 2500 3000
Time, min
Tem
per
atu
re,
oC
Electrolyte
CDL w/o electrolyte
CDL w/electrolyte
CDL w/all components
CESE November 13, 2009November 13, 2009
A conceptual road map for the thermal runaway A conceptual road map for the thermal runaway in Li-ion cellsin Li-ion cells
Need nonflammableNeed nonflammableelectrolyteselectrolytes
Cathode SEI/Elect. Cathode SEI/Elect.
O2 Evolution
T> 85oC
Solvent/Salt H = 200 J/g H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
T > 200oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
T> 85oC
Solvent/Salt H = 200 J/g
T > 140oCT > 140oC H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
Need stable cathodeNeed stable cathode
Need nonflammableNeed nonflammableelectrolyteselectrolytes
Cathode SEI/Elect. Cathode SEI/Elect.
O2 Evolution
T> 85oC
Solvent/Salt H = 200 J/g H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
T > 200oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
T> 85oC
Solvent/Salt H = 200 J/g
T > 140oCT > 140oC H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
T> 85oC
Solvent/Salt H = 200 J/g H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
T > 200oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
T> 85oC
Solvent/Salt H = 200 J/g
T > 140oCT > 140oCT > 140oCT > 140oC H = 300 J/g
LiNi0.8Co0.2O2 /Elect. H = 500 J/g
T > 180oC
oC
T > 660oC
LixC6 /PVDF/O2 /Elect.H = 1500 J/g Fire
Aluminum MeltdownH = -395J/g
High Rate Abusive Conditions Internal Shorts
Anode SEI/Elect.H = 350 J/g
Need stable cathodeNeed stable cathode
Stable SEI filmsStable SEI films
CESE November 13, 2009November 13, 2009
Approaches to improve thermal safety of Li-ion cells Approaches to improve thermal safety of Li-ion cells
Use of additives to form stable SEI film » Stable SEI film decomposes at higher temperature
» Avoids the secondary SEI formation
» Delay the initiation of thermal runaway
Thermally stable cathodes» Stable spinel oxides
» Core-shell cathodes (Hanyang university)
Nonflammable electrolytes» Flame retardant additives
» Nonflammable solvents
CESE November 13, 2009November 13, 2009
Effects of VC, VEC and LiBOB additives on the Effects of VC, VEC and LiBOB additives on the thermal behavior of anode thermal behavior of anode
-5
-4
-3
-2
-1
0
60 110 160 210 260 310 360
Temperature (oC)
Hea
t ra
te,
Exo
up
(W
/g)
2wt % VEC
2 wt % VC
2wt % LiBOB
No additive
-2
-1
0
60 80 100 120 140 160 180 200Temperature (oC)
Hea
t ra
te,
Exo
up
(W
/g) 2wt % VEC
2 wt % VC
2wt % LiBOB
No additive
CESE November 13, 2009November 13, 2009
Electrolyte modification: FR additivesElectrolyte modification: FR additives
Cathode
0
0.8
1.6
2.4
3.2
4
50 100 150 200 250 300Temperature, oC
Hea
t F
low
, W/g
EX
O U
P
Without HMTPWith 1.5 wt% of HMTP
216 oC
241 oC
0
0.5
1
1.5
2
50 100 150 200 250 300
Temperature, oC
Hea
t F
low
, W/g
EX
O U
P
Without HMTPWith 1.5 wt% of HMTP
235 oC
243 oC
120 oC131 oC
Anode
N
PN
P
NP
OCH3
OCH3H3CO
H3CO
OCH3H3CO
Hexa-methoxy-cyclo-tri-phosphazene(HMTP)
N
PN
P
NP
OCH3
OCH3H3CO
H3CO
OCH3H3CO
Hexa-methoxy-cyclo-tri-phosphazene(HMTP)
CESE November 13, 2009November 13, 2009
Core-Shell approach to improve thermal safetyCore-Shell approach to improve thermal safety
50 100 150 200 250 300-25
0
25
50
75
100
125
150
175
200
225
Temperature (oC)
Delayed Reaction
Thermal Runaway Start
Core Shell cellCore cell
Sel
f H
eat
Rate
(oC
/min
) Temperature (oC)50 100 150 200 250 300-25
0
25
50
75
100
125
150
175
200
225
Temperature (oC)
Delayed Reaction
Thermal Runaway Start
Core Shell cellCore cell
Sel
f H
eat
Rate
(oC
/min
) Temperature (oC) 50 100 150 200 250 300 3501E-3
0.01
0.1
1
10
100
1000
Thermal runaway delayed by ~50oC delay
Reaction start (Cathode + Electrolyte)
Anode reaction (Decomposition of SEI)
Core ShellCore
Self
He
at
Rate
(o C
/min
)
Temperature (oC)
5050ooC delayC delay ARCARC
0
10
20
30
40
50 100 150 200 250 300 350 400
Temperature (oC)
Core-Shell charged to 4.3V
SOA cathode Charged to 4.3V
0
10
20
30
40
50 100 150 200 250 300 350 400
Heat
Flo
w (W
/g)
Core-Shell charged to 4.3V
SOA cathode Charged to 4.3V
5050ooC delayC delay
DSCDSC
Shell
Core
Shell
Core
Li[NiLi[Ni0.50.5MnMn0.50.5]O]O22
LiNiLiNi0.80.8CoCo0.10.1MnMn0.10.1OO22
CESE November 13, 2009November 13, 2009
AcknowledgmentsAcknowledgments
Dr. Evren Gunen Dr. H. Bang Dr. Hui Yang Dr. C. Lee
Dr. D. Dess (ANL) Dr. K. Amine (ANL) Prof. Y. K. Sun (Hanyang U., S.
Korea