electrode - electrolyte interface studies in lithium batteries
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1/29
Nicolas Dupré, Dominique Guyomard
Institut des Matériaux Jean Rouxel ‐ Université de Nantes, France
Kouta Suzuki, Masaaki Hirayama, Ryoji Kanno
Tokyo Institute of Technology, Japan
Electrode/Electrolyte Interface Studies in Lithium Batteries
Marine Cuisinier
University of Waterloo, Canada
2/33
10 100 1000
Po
we
r (W
/ k
g)
Energy (Wh/kg)
10
100
1000
Pb-acid
HEV
EV
PHEV, power tools Li-ion
Energy (Wh/kg, Wh/l)
Power (W/kg, W/l)
Life
Safety
Cost
Toxicity
Reactivity at interfaces
btw. electrodes & electrolyte
Safety
Long term cyclability
Energy Autonomy Power Rate, acceleration
Li-ion & related challenges
Ni-MH
3/33
Aging mechanisms of cathode materials
dissolution
re-precipitation of new phases
surface layer formation
electrolyte decomposition
migration of soluble species
gas evolution
Adapted from J. Vetter et al., J. Power Sources 147 (2005) 269
O O
O
O O
OLi
EC DMC
PFF F
F
F
F
LiF
ROCO2Li LixPOyFz
OPF2(RO)nF
4/29
Table of contents
CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE
CHARACTERIZATION METHODS 1
Review of interface characterization methods
MAS NMR applied to surface species analysis
Intrinsic interphasial behavior
Surface aging upon storage: characterization and control towards improved electrochemical performance
GENERAL CONCLUSION & PERSPECTIVES
3
4
EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE
Aging upon storage in LiPF6 electrolyte
Aging upon cycling in LiPF6 and LiBOB modified electrolyte
2
5/33
Classical interface characterization methods
NMR
From Reuters, Web of Knowledge
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0
10
20
30
40
50
Pu
blish
ed
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year
Publication year
FTIR
XPS
MAS NMR
A strategy for R&D of Li and Li-ion batteries.
Study of Electrodes Li, Li-C anodes and LixMOy cathodes.
Surface Chemistry
in situ & ex situ FTIR, XPS,
EDAX, EQCM
Morphology
in situ AFM (SEM)
Interfacial properties
EIS, B.E.T. (surface area)
Structural analysis
in situ & ex situ XRD (SEM)
Electroanalytical behavior of Li
insertion compounds
PITT, EIS, SSCV
Solution studies
Electrochemical windows, thermal
stability, redox processes:
CV, in situ FTIR, EQCM, EIS, DTA
Correlation
Optimization of electrolyte
solutions
Performance
Fast tests for cycling efficiency
(GCPL)
Testing in practical cells
(coin cells and AA cells)
6/33
Review of interface studies by NMR
< 20 studies in the literature on « passivation layer on LiB materials »
Suitable for: 1H, 7Li, 13C, 19F and 31P in the interphase… or 23Na !
7/33
3
0 1..
4 rDµH ijeen
7Li NMR: Li-electron dipolar interaction
Distance between Li and paramagnetic center
Li (nuclear spin)
O B0
Mn4+ t2g
r Through space
(unpaired electron spin)
Coupling between nuclear spin and electronic spin (paramagnetic ions)
q
8/33
t0
Free Induction Decay π/2 pulse
T2para
Bulk Surface
acquisition
If r ↓ Hen ↑ then T2 ↓
Using 7Li MAS NMR to selectively DETECT the interphase
DEAD TIME (5-50 s) before acquisition of data
REMOVE Li-bulk SIGNAL
Distance between Li and paramagnetic center
Time
Mn
Li
Li
Longer T2
Short T2
T2 para
x
y B0
Surface species = diamagnetic (Li2CO3, LiF, LixOyPFz etc…)
3
0 1..
4 rDµH ijeen
9/33
-2000-10000100020003000
(ppm)
c
b
a
7Li, 500MHz, 14kHz
Li2CO3 powder
LiNi0.5Mn0.5O2 with surface Li2CO3
Surface
Li2CO3
Bulk
Dead time
No dead time
Dipolar
interaction 0 ppm
Diamagnetic
surface species
DIPOLAR INTERACTION
THICKNESS / INTIMACY of the interphase with the bulk
Ménétrier, M. et al. Electrochem. And Solid State Lett., 2004, 7(6), A140.
Dupré, N. et al. J. Mat. Chem., 2008, 18, 4266
Using 7Li MAS NMR to study electrode/interphase interactions
If r ↓ Hen ↑ then T2 ↓
If µe ↑ Hen ↑ then T2 ↓
-40-2002040
2 V4.5 V
7Li / ppmm
Dipolar
interaction
2
1
TFWHM
10/33
7Li, 19F and 31P NMR spectra calibration curves
From known amounts of diamagnetic nuclei (LiF, LiPF6)
Works for interphases grown on
≠ electrode materials: LiMn0.5Ni0.5O2 , LiFePO4 , Si
Absolute quantification
of interphasial [Li], [F], [P]
in mmol.g-1 or mmol.m-²
Using MAS NMR to QUANTIFY the interphase
0 25 50 75 100
inte
gra
ted
in
ten
sit
y /
NS
/ R
G (
a.
u.)
diamagnetic Li (µmol)
y = 4.26 10-1x
LiF / LiPF6 calibration
LiFePO4
LiMn1.5
Ni0.5
O4
Si
0
10
20
30
40
50
0 25 50 75 100
0
1
2
3
4
5
y = 2.80 10-2 x
LiPF6 calibration
inte
gra
ted
in
ten
sit
y / N
S / R
G
y = 6.38 10-2 x
LiF calibration
diamagnetic F (µmol)
LiMn1.5
Ni0.5
O4
LiFePO4
Si
19F NMR
7Li NMR
11/33
Interpretation of quantitative NMR results
OX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Charge statedia
mag
neti
c L
i o
r F
(m
mo
l.g
-1)
7Li
19F / PF
19F / LiF
7Li, 19F NMR
Total Li (7Li NMR)
Fluorophosphates (19F NMR)
Li in organic ~ Total Li (7Li) – LiF (19F) ?
POF3/PO2F2-/ PO3F2-
O OR
O
Li+
OO
OLi Li
(Li-alkylcarbonates)
(Li2CO3)
PO
R
O
F
F
LiF (19F NMR)
nO O
O OO
O
PO
O
F
FLior
Non lithiated organic species remain invisible to our NMR experiments
12/33
Need for COMPLEMENTARY analytical tools
5 0 n m
LiPFLiPF66 electrolyteelectrolyte
decompositiondecomposition
LiMnLiMn0.50.5NiNi0.50.5OO22
interphaseinterphase
formationformation
5 0 n m
LiPFLiPF66 electrolyteelectrolyte
decompositiondecomposition
LiMnLiMn0.50.5NiNi0.50.5OO22
interphaseinterphase
formationformation
Electrode active Electrode active materialmaterialElectrode active Electrode active materialmaterial
DiamagneticDiamagnetic interphasesinterphases
Electrode active Electrode active materialmaterial
NMR XPS
Electrode active Electrode active materialmaterialElectrode active Electrode active materialmaterial
DiamagneticDiamagnetic interphasesinterphases
Electrode active Electrode active materialmaterial
NMR XPS
Electrode active Electrode active materialmaterialElectrode active Electrode active materialmaterial
DiamagneticDiamagnetic interphasesinterphases
Electrode active Electrode active materialmaterial
NMR XPS
Electrode active Electrode active materialmaterialElectrode active Electrode active materialmaterial
DiamagneticDiamagnetic interphasesinterphases
Electrode active Electrode active materialmaterial
NMR XPS
TEM/EELS
Brookhaven Nat. Lab. Z’/Ω
Z’’/Ω
-50
-25
50 100 0 25 75
Rel
Nyquist plot Rinterfacial
In situ EIS
13/29
Table of contents
CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE
CHARACTERIZATION METHODS 1
Review of interface characterization methods
MAS NMR applied to surface species analysis
Intrinsic interphasial behavior
Surface aging upon storage: characterization and control towards improved electrochemical performance
GENERAL CONCLUSION & PERSPECTIVES
3
4
EXAMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE
Aging upon storage in LiPF6 electrolyte
Aging upon cycling in LiPF6 and LiBOB modified electrolyte
2
14/33
Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (SEM)
1000 500 0 -500 -1000 200 0 -200 -400
no
rmali
zed
/ N
S /
RG
/m
7Li / ppm
30 sec.
3 days
2 weeks
1 hour
5 min.
1 min.
0 ppm
no
rmali
zed
/ N
S /
RG
/m
19F / ppm
LiF
-205 ppm
1 µm
1 µm
(a) (b) (c)
1 µm
19F NMR 7Li NMR
Soaking at RT in LiPF6 1M, EC:DMC (1:1)
Surface “film” observation by SEM
19F: LiF only
Pristine
3 days
1 month
15/33
0 10 20 30 40 50 600.0
0.1
0.2
0.3
0.4
300 400 500 600 700
One month
7Li NMR
19F NMR
mm
ol (L
i o
r F
) / g
LM
N
Contact time (min) Contact time (h)
Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (NMR vs XPS)
19F: LiF only
XPS: LiF screening by Li-containing organic species
7Li, 19F NMR
Li in organic = Total Li (7Li)
– LiF (19F)
LiF
LixPFy
LixPOyFz
XPS F1s
1 month
1 hour
5 min. 37%
33% 26%
XPS C1s
CO2
CO
CC/CH
13%
16%
26% 1 month
1 hour
5 min.
CO3
16/33
Example 1: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon storage (EELS)
LMN½
PF5 + LiF
LiPF6
Salt decomposition Solvents decomposition
Contact time
O OR
O
Li+
O O
O
Ni-L2,3
Mn-L2,3
500 600 700 800 900
8
7
6
5
4
O-K
F-K
Energy Loss (eV)
3
8
5
8 7 6 5 4 30
20
40
60
80
100
% Mn
% F
% Oato
mic
%
spot number
EELS
Interphase growth scenario:
17/33
Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (1)
0 5 10 15 20
100
120
140
160
180
200
220
0 5 10 15 20
25
50
75
100
125
Q charge
Q discharge
Cap
acit
y (m
A.h
.g-1
)
Cycle number
50
60
70
80
90
100
Coulombic efficiency
Co
ulo
mb
ic e
ffic
ien
cy
(%
)
Rct 4.5 V
Rct 2 V
Ch
arg
e t
ran
sfe
r re
sis
tan
ce
(
)
Cycle number
LiPF6 0.9M + LiBOB 0.1MLiPF
6 1M
0 5 10 15 20 25 30
0
5
10
15
20
25
30
Z' / .mg-2
20th
ox
5th
ox
Z"
/
.mg
-2
1st ox
0 5 10 15 20 25 30
0
5
10
15
20
25
30
Z' / .mg-2
20th
ox
5th
ox
Z"
/
.mg
-2
1st ox
0 5 10 15 20
100
120
140
160
180
200
220
Q charge
Q discharge
Cap
acit
y (m
A.h
.g-1
)
Cycle number0 5 10 15 20
100
120
140
160
180
200
220
Cap
acit
y (m
A.h
.g-1
)
Cycle number
Q charge
Q discharge
0 5 10 15 20
100
120
140
160
180
200
220
0 5 10 15 20
25
50
75
100
125
Q charge
Q discharge
Cap
acit
y (m
A.h
.g-1
)
Cycle number
50
60
70
80
90
100
Coulombic efficiency
Co
ulo
mb
ic e
ffic
ien
cy
(%
)
Rct 4.5 V
Rct 2 V
Ch
arg
e t
ran
sfe
r re
sis
tan
ce
(
)
Cycle number
1st charge: parasitic electrochemical process
Impedance ↑ : only Rct ↑
18/33
PRISTINEOX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dia
ma
gn
eti
c L
i/F
(m
mo
l/g
)
Charge state
19
F / LiF
19
F / PF
7Li
0.0
0.1
0.2
0.3
0.4
0.5
0.6
T2(L
i) (
ms
)
PRISTINEOX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dia
ma
gn
eti
c L
i/F
(m
mo
l/g
)
Charge state
19
F / LiF
19
F / PF
7Li
0.0
0.1
0.2
0.3
0.4
0.5
0.6
T2(L
i) (
ms
)
Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (2)
O OR
O
Li+
PO
O
F
FLi
0 5 10 15 20
100
120
140
160
180
200
220
0 5 10 15 20
25
50
75
100
125
Q charge
Q discharge
Cap
acit
y (m
A.h
.g-1
)Cycle number
50
60
70
80
90
100
Coulombic efficiency
Co
ulo
mb
ic e
ffic
ien
cy
(%
)
Rct 4.5 V
Rct 2 V
Ch
arg
e t
ran
sfe
r re
sis
tan
ce
(
)
Cycle number
0 5 10 15 20
100
120
140
160
180
200
220
0 5 10 15 20
25
50
75
100
125
Q charge
Q discharge
Cap
acit
y (m
A.h
.g-1
)
Cycle number
50
60
70
80
90
100
Coulombic efficiency
Co
ulo
mb
ic e
ffic
ien
cy
(%
)
Rct 4.5 V
Rct 2 V
Ch
arg
e t
ran
sfe
r re
sis
tan
ce
(
)
Cycle number
Appearance of fluorophosphates
Electrochemical formation of the interphase?
200 0 -200 -400
no
rma
lize
d / N
S / R
G /m
19
F / ppm
OX 1
RED 1
19F NMR
Indirect electrochemical oxidation: oxygen transfer from the oxide surface to the solvent molecules
S.-W. Song et al., JES, 151, A1162 (2004)
LMN½ LMN½
Fluorophosphates
Organic species
LiF nO O
O OO
O
PO
R
O
F
F
Li-free organic
19/33
Example 2: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (3)
PRISTINEOX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dia
ma
gn
eti
c L
i/F
(m
mo
l/g
)
Charge state
19
F / LiF
19
F / PF
7Li
0.0
0.1
0.2
0.3
0.4
0.5
0.6
T2(L
i) (
ms
)
Li-poor interphase:
LiF + non-lithiated species
T2(Li): No evolution of the AM /interphase intimacy
Stable (resistive) LiF-based interphase + growing non-lithiated (PEO type + phosphates)
M. Cuisinier et al. Solid State Nucl. Magn. Reson. 42, 51 (2011)
20/33
PRISTINE OX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dia
mag
neti
c F
(m
mo
l/g
)
dia
mag
neti
c F
(m
mo
l/g
)
dia
mag
neti
c L
i (m
mo
l/g
)
Charge state
19F / LiF
19F / PF
7Li
PRISTINE OX1 RED1 OX5 RED5 OX20 RED20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dia
mag
neti
c L
i (m
mo
l/g
)
Charge state
19F / LiF
19F / PF
7Li
Cathode protecting agent
Mn-containing insoluble surface layer [*]
LiBOB
Composition of interphase is different: Presence of Li in org. species / fluorophosphates
[*] Chen, Z. et al., Electrochim. Acta 51 (2006) 3322.
« good » interphase ↑ electrochemical performance
0
5
10
15
20
25
30
0 5 10 15 20 25 30
BOB-1oxBOB-5oxBOB-20ox
Z'' /
Oh
m
Z' / Ohm
0
50
100
150
200
0 50 100 150 200
PF6-1oxPF6-5oxPF6-20ox
Z'' /
Oh
m
Z' / Ohm
Example 3: aging of the LiNi1/2Mn1/2O2 / LiPF6 interphase upon cycling (effect of LiBOB additive)
No LiBOB
Less resistive interphase
21/29
Table of contents
CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE
CHARACTERIZATION METHODS 1
Review of interface characterization methods
MAS NMR applied to surface species analysis
Interphase dynamics upon voltage variations
Interphase modeling using ideal 2D films
Interphase evolution upon extended cycling
GENERAL CONCLUSION & PERSPECTIVES
3
4
EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE
Aging upon storage in LiPF6 electrolyte
Aging upon cycling in LiPF6 and LiBOB modified electrolyte
2
22/33
4V 4.5V 2.7V 2V 2.7V 4.5V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Charge state
dia
mag
neti
c L
i o
r F
(m
mo
l.g
-1)
7Li
19
F/PF
19
F/LiF
Evolution of the LiFePO4 interface with voltage
7Li/19F: clarify XPS stable inorganic interphase
+ fluctuating organic species
FePO4
Oxidized state
LiFePO4
Reduced state
Fluorophosphates
Li-organic species
LiF
4.5 V 4.5 V 2.7 V 2.7 V 2.0 V 4.0 V
Interphase model:
Solid Polymer Layer
F. Croce et aL., J. Power Sources, 43 (1993) 9
23/33
Modeling the interphase architecture (1)
-20 0 20 40 60 80 100
20
40
60
80
100
500 550 600 650 700 750 800
% O
% F
% Fe
Ele
me
nta
l p
erc
en
tag
e (
%)
Distance from the surface (nm)
F-KO-K
#12: 14 nm
#11: 19 nm
#10: 18 nm
Energy loss (eV)
#6: AMFe L
2,3
EELS: Any multi-layered model is abusive ! (at least on powder samples)
EELS
24/33
Model surface: a- oriented LiFePO4 thin films
Pulsed Laser Deposition: 20-80nm thick LiFePO4 epitaxial film on SrTiO3 (010)
TEM-EELS
Pristine film: structurally homogeneous Possibility to monitor fine surface structure changes upon Li (de)intercalation
a- oriented LiFePO4 thin films
520 525 530 535 540 545 550 555
energy loss (eV)
690 700 710 720 730 740
energy loss (eV)
Fe-L2,3O-K
Ideal 2D surface
= model interphase
Subjected to storage in LiPF6 electrolyte and cycling
Validate the interphase model?
Pulsed Laser Deposition: 20-80nm thick LiFePO4 epitaxial film on SrTiO3 (010)
TEM-EELS
Pristine film: structurally homogeneous Possibility to monitor fine surface structure changes upon Li (de)intercalation
a- oriented LiFePO4 thin films
520 525 530 535 540 545 550 555
energy loss (eV)
690 700 710 720 730 740
energy loss (eV)
Fe-L2,3O-K
1.080.551.06Roughness
t / nm
-20.361.33Thickness
l / nm
5.123.622.11Density
d / g·cm-3
SrTiO3
LiFePO4
Surface
layer
1.080.551.06Roughness
t / nm
-20.361.33Thickness
l / nm
5.123.622.11Density
d / g·cm-3
SrTiO3
LiFePO4
Surface
layer
SrTiO3 substrate
LiFePO4
glue
SrTiO3 substrate
LiFePO4
glue
(a)
(b)
(c)
(d)
Pulsed Laser Deposition: 20-80nm thick LiFePO4 epitaxial film on SrTiO3 (010)
TEM-EELS
Pristine film: structurally homogeneous Possibility to monitor fine surface structure changes upon Li (de)intercalation
a- oriented LiFePO4 thin films
520 525 530 535 540 545 550 555
energy loss (eV)
690 700 710 720 730 740
energy loss (eV)
Fe-L2,3O-K
1.080.551.06Roughness
t / nm
-20.361.33Thickness
l / nm
5.123.622.11Density
d / g·cm-3
SrTiO3
LiFePO4
Surface
layer
1.080.551.06Roughness
t / nm
-20.361.33Thickness
l / nm
5.123.622.11Density
d / g·cm-3
SrTiO3
LiFePO4
Surface
layer
SrTiO3 substrate
LiFePO4
glue
SrTiO3 substrate
LiFePO4
glue
(a)
(b)
(c)
(d)
Hirayama et al., Electrochemistry (Tokyo), 5 (2010) 413
25/33
Modeling the interphase architecture (2)
3λ
Electron detector
X-ray
3λ. s
in(θ
)
Bulk Surface
θθ
3λ.c
os(θ)
Modeling the interphase architecture
3λ
Electron detector
X-ray
3λ. s
in(θ
)
Bulk Surface
XPS
Penetration depth = 3λ.sin(θ) with λ~27Å
θ varied from 0° to 60°I(θ)= Iinf . exp(-d/λ.cosθ)
d, the interphase thickness
3
3.5
4
4.5
5
1 1.2 1.4 1.6 1.8 2
air contact4.5V 1st charge2.5V 1st discharge
1/cos(q)
LN
(P-O
)
1.2 nm1.7 nm0.8 nm
2.5V4.5Vpristine
1.2 nm1.7 nm0.8 nm
2.5V4.5Vpristine
-0.2
0
0.2
0.4
0.6
0.8
1
PO Fe LiF PF CO CO2
4.5V 1st charge2.5V 1st discharge
LN
(su
rfa
ce
/bu
lk)
Interphase depth profile:
bulk
surface
Confirms NMR and EELS results:Inner LiF, covered by fluorophosphates
and a dynamic Solid Polymer Layer (SPL)
Penetration depth = 3λ.cos(θ)
with λ ~ 22 Å
1.0 1.2 1.4 1.6 1.8 2.0
0.4
0.6
0.8
1.0
1.2
1.4
1.6
dried
4.5 V
2.5 V
ln C
(Fe 2
p1/2)
1/cosq -1
d (nm)
Pristine 0.44
1st ox. 4.5 V 1.4
1st red 2.5 V 0.25
Average λ (inelastic mean free path) is inaccurate !
XPS
Voltage dependance of the interphase thickness
% 6
- d
26/33
690 688 686 684 682 PO Fe LiF PF CO2 CO ---0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
F 1s
LixPO
yF
z
LiF
C.P
.S
Binding energy (eV)
q = 60°
q = 55°
q = 48°
q = 37°
q = 0°
1st Red
2.5 V
1st Ox
4.5 V
FePO4
LiF
OPF2OMe, OPF2(OCH2CH2)nF
CH2CO2Li, ROCO2Li
LiFePO4
LiF
OPF2OMe, OPF2(OCH2CH2)nF
CH2CO2Li, ROCO2Li
Modeling the interphase architecture (3)
3λ
Electron detector
X-ray
3λ. s
in(θ
)
Bulk Surface
θθ
3λ.c
os(θ)
690 688 686 684 682 PO Fe LiF PF CO2 CO-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2F 1s
LixPO
yF
z
LiF
C.P
.S
Binding energy (eV)
q = 60°q = 55°
q = 48°
q = 37°
q = 0°
1st Red - 2.5 V
kA 1st Ox - 4.5 VXPS
Inner interphase: stable / inorganic
Outer interphase : dynamic / polymeric
)0%(
)60%(
C
C
27/33
0 20 40 60 80 100
0
20
40
60
80
100
0 20 40 60 80 100
0
20
40
60
80
100
250 Hz
1 ox 4.5 V
5 ox 4.5 V
20 ox 4.5 V
-Z'' /
Z' /
6 kHz
-Z'' /
Z' /
1 red 2V
5 red 2V
20 red 2V
5 kHz
100 Hz
1 20
5 1
20
5
Pristine - 4.5 V Pristine - 2 V
OX1 RED1 OX5 RED5 OX20 RED20
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
0.5
Charge state
dia
mag
neti
c L
i o
r F
(m
mo
l.g
-1)
7Li
19F / PF
19F / LiF
7Li, 19F NMR
0 20 40 60 80 100
80
100
120
140
160
180
Dis
ch
arg
e c
ap
ac
ity (
mA
.h.g
-1)
cycle number
Stable impedance, no resistive film
Accumulation of interphase species
Stable performance vs Li No resistive film
Lots of Li outside LiF, in LixPOyFz (?),
in Li-organic (1H NMR, XPS)
Interphase data upon cycling for bare LFP
O OR
O
Li+P
O
O
F
FLi
Charge transfer
1 ox 5 ox 20 ox 1 red 5 red 20 red
28/33
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
Inte
rph
asia
l 7L
i (m
mo
l.g
-1)
T2(L
i) (
ms)
20 ox 20 red5 red5 ox1 red1 ox
Interphase growth scenario for bare LFP
7Li NMR
T2(Li): decreasing intimacy
Signal integration: accumulation of surface Li
Non blocking interphase,
But no passivation:
Interphase growth by stacking
Stable performance vs Li No resistive film
Li-rich porous interphase
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
Interphasial 7Li (mmol.g
-1)
T2(Li)
(ms)
20 o
x20 re
d5 re
d5 o
x1 re
d1 o
x
FePO4
Oxidized state
LiFePO4
Reduced state
Li+ Li+
Fluorophosphates
Li-organic species
LiF
M. Cuisinier et al. J. Power Sources, 224, 50 (2013)
LMN½ LMN½
Fluorophosphates
Organic species
LiF nO O
O OO
O
PO
R
O
F
F
Li-free organic
29/33
STABLE REVERSIBLE “BREATHING”
STABLE PERFORMANCE
STABLE REVERSIBLE “BREATHING”
STABLE PERFORMANCE
Stable performance require a Li-rich organic interphase
How to stop Li consumption in it?
Poor performance of our LMN material might be assigned to a “bad” interphase: no Li mobility, growing Li-free matrix on LiF-rich inner interphase
The case of LiFePO4: summary vs. LiMn1/2Ni1/2O2
LFP FP
M. Cuisinier et al. Solid State Nucl. Magn. Reson. 42, 51 (2011)
M. Cuisinier et al. J. Power Sources, 224, 50 (2013)
30/29
Table of contents
CASE OF THE LIFEPO4/ELECTROLYTE INTERPHASE
CHARACTERIZATION METHODS 1
Review of interface characterization methods
MAS NMR applied to surface species analysis
Intrinsic interphasial behavior
Surface aging upon storage: characterization and control towards improved electrochemical performance
GENERAL CONCLUSION & PERSPECTIVES
3
4
EXEMPLES: LINI0.5MN0.5O2/ELECTROLYTE INTERPHASE
Aging upon storage in LiPF6 electrolyte
Aging upon cycling in LiPF6 and LiBOB modified electrolyte
2
31/33
Need for powerful analytical tools Validation of NMR for interphase studies (perspectives)
Use for full cells and negatives: Si or intermetallics Use for the exploration of Na interphasial chemistry
(NaClO4 NaTFSI?) even more critical at the negative
T1/T2(Li) mapping = principle of MRI ! use to localize liquid/confined/solid state Li in the battery
Battery performance is driven by surface chemistry
GENERAL CONCLUSION & PERSPECTIVES
32/33
Interphase evolves upon voltage variations, depending on the AM
No general formation mechanism Complex architecture/composition conducting properties
Good interphase = SEI-like
Li-O-rich to be conducting Dense to passivate the AM surface Thin to limit Li consumption Not straightforward tailor with additives or new electrolytes NMR for the diagnostic evaluation of detrimental phenomena
Cross-talk between the negative and positive interphases
Need for parallel studies on both electrodes
Battery performance is driven by surface chemistry
GENERAL CONCLUSION & PERSPECTIVES
33/33
Nicolas Dupré, Dominique Guyomard but also L. Lajaunie, J.-F.
Martin, P. Moreau, Z.-L. Wang (co-workers)
R. Kanno, M. Hirayama, K. Suzuki, S. Taminato (Tokyo Tech collab.)
K. Edström (Uppsala), T. Épicier (INSA Lyon), L. Croguennec,
M. Ménétrier & A. Wattiaux (ICMCB), J.-M. Tarascon (LRCS),
J. Cabana (LBNL) for fruitful discussions and experimental
contributions
MESR, METSA (funding)
marine.cuisinier@gmail.com
nicolas.dupre@cnrs-imn.fr
Acknowledgments
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