electrochemistry and electrochemical ´723,&$/352%...
TRANSCRIPT
The anionic redox activity:
From fundamental understanding to
practical challenges
1st International Conference of Young Scientists
“TOPICAL PROBLEMS OF MODERN
ELECTROCHEMISTRY AND ELECTROCHEMICAL
MATERIALS SCIENCE”
September 17th, 2017
J.M. Tarascon
http://www.college-de-france.fr/site/en-college/index.htm
Contents
General remarks on insertion compounds ► Setting up the problem
Conclusions and perspectives
► Emergence of the anionic redox prcess
The science underlying the anionic redox process
Widening the spectrum of oxides showing anionic redox
Practicality of Li-rich oxides: a mixed blessing
The Chemistry and Physics of Insertion Reactions
[Ti+4S2] + Li+ + e- [LiTi+3S2]
e -
e -
e -
e - e -
e -
e - -e -
e -
[H] + x A n++ xn e- [AxH][H] + x A n++ xn e- [A
xH]n+ x ne-
e-
Matériauhôte
EspèceInvité
Oxy + e- Red
Red Oxy + e-
The crystallographic structure
1D
3D
Open structures (tunnels, layers, ...)
Cristallographic structure
2D
e- Li+
e-
e-
Li+
Li+
e-
e-
e-
e-e-
e-
e-
e-
e-Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+e- Li+
e-
e-
Li+
Li+
e-
e-
e-
e-e-
e-
e-
e-
e-Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
se
si
Duality ions/electrons
The electronic band structure
N (E)
E (eV)
s, p
t2g
p
s
Ef
e- from MO*
x in LiCoO2
Li
M
O
Cationic
framework
Anionic
framework
LIB has relied on cationic redox reactions This is no longer true since 2013
The anionic redox activity: a transformational change
150 mAh/g 280 mAh/g
NATURE MATERIALS, 2013, 12, 827-835 . NATURE MATERIALS | VOL 14 | FEBRUARY 2015, SCIENCE, 2015, 305 (6267)
(2D Layered oxide) (2D Li-rich layered oxide)
Ligand-hole chemistry in chalcogenides Rouxel (1991)
Oxygen activity in LiCoO2 proposed / theory confirmed it
Tarascon / Ceder (1999)
Synthesis of Li-rich Li2MnO3-based cathodes
Dahn / Thackrey (2002-2007)
The Emergence of Anionic Redox
Oxygen redox in Li2RuO3 and Li2IrO3 – Direct proofs
Tarascon (2013-2016)
Oxygen redox in Li-rich cathodes – Theory
Ceder / Doublet (2016)
vs.
Oxygen redox in Li-rich NMC – Direct proofs
Bruce (2016)
Oxygen activity in LiCoO2 - Experiments
Yoon / Dedryvère (2002-2008)
Suspecting oxygen redox in Li-rich NMC
Delmas (2012)
Anionic redox : It’s emergence
6
Pyrite FeS2 Layered TiS2 Metal electronegativity
2 S-- (S2)
2- + 2e-
Mm+ M(m-1)+ - e-
Creation of ligand
holes and S22- pairs
Rouxel, Chem. Eur. J., 2, 1996
Anionic redox in chalcogenides: Rouxel’s pioneering work in the 1990’s
Ti4+ (S2-) (S2)
Li2.2Ti4+0.8Ti+3
0.2 S3
LixTiS3
x= 0
x= 1
x= 1.8
x= 2.2
Li1Ti4+ (S2-)2 (S2)0.5
Li1.8Ti4+ (S2-)2.8 (S2)2-
0.1
M.H. Lindic et al Solid State Ionics, 176 (2005) 1529 – 1537
Dimère
S22-
Anion
S2-
2-
2-
Experimental evidence of the S participation to the redox process by XPS
5.5
5.0
4.5
4
3.5
3.0
2.50.0 0.2 0.4 0.6 0.8 1.0
x in LixCoO2
Pote
ntie
l (V
vs.
Li+
/Li
)
Existence of CoO2 ? No longer a mystery
Chemical oxidation
(Br2, NO2BF4)
Electrochemical oxidation
G.G. Amatucci, J.M. Tarascon, et al. , J. Electrochem. Soc., Vol. 143, N°3, March 1996 J.M. Tarascon et al. Jr. of Solid State Chemistry 1999
LiCoO2 CoO2 Li1-x (CdI2 Structure)
d
EF
Chemical/electrochemical approaches
DOS sp
En
erg
ie
N() DOS
spE
ne
rgy
N()
Co4-x(O2-)2-2x (O22-)x
CoO2
A few intriguing results which were overlooked
J. Dahn et al. Journal of The Electrochemical Society, 2002
3.0 – 4.4V
2.0 – 4.8V
240 mAh/g
Li(Li0.16Ni0.25Mn0.58)O2
► Extra-capacity triggers by oxygen deficiency
P. Kalyani et al, Journal of power source (1999)
Li2MnO3
► Removal of O2- plus exchange of Li+ by H+
O 1s core peaks in delithiated LixCoO2 compounds
CoO2
LiCoO2
R. Debryvére, et al. Chem. Mater. 2008
Deintercalation from LiCoO2 to CoO2 investigated by XPS
LiCoO2 has been the “stellar” material for numerous years
0.0 0.5 0.6 0.7 0.9 1.03.0
3.5
4.0
4.5
5.0150 120 90 60 30 0
0.0 0.2 0.4 0.6 0.8 1.03.0
3.5
4.0
4.5
5.0250 200 150 100 50 0
≈
≈
Vo
ltage
(V
vs.
Li+
/Li0
)
Capacité (mAh/g)
x in Li1-x CoO2
150 mAh/g
x in LixCoO2
Li0.5CoO2
Dahn et al. , Chemistry of materials 15, (2003),3214-3220
Improvements via chemical substitutions:
Li[Co]O2
[150 mAh/g]
Replace partiallyCo by
Mn et Ni
Li[NiMnCo]O2
[180 mAh/g]
NMC phases
The LixCO2 system and its evolution
T.Ohzuku, Y. Makimura; Chem Lett. 642 (2001)
New Li-rich high-capacity layered oxides
M Thackeray. J/ Mat. Chem 15, 2257 (2005)
Li[LiCoNiMn]O2
Co Ni
Mn
Li-excess
Capacity mAh /g
High capacity (> 280 mAh/g)
?
Vol
tage
(V
olts
vs.
Li+/L
i)
Li1[Li0.2Ni0.15Mn0.48Co0.17]O2
Solid Solution(1-z) [Li1/3Mn1/3]O2 – (z)Li[Mn0.5-yNi0.5-yCo2y]O2
Composites (1-z) [Li1/3Mn1/3]O2 – (z)Li[Mn0.5-yNi0.5-yCo2y]O2
(Dahn:3M)
Dahn et al. , Chemistry of materials 15, (2003),3214-3220
300 200 100 0 Capacité en mAh/g
Pote
ntiel (V
olts v
s. Li+
/Li
)
0.0 0.2 0.4 0.6 0.8 1.0
2.0
2.5
3.0
3.5
4.0
4.5
050100150200250
4.0
4.5
3.5
3.0
2.5
5.0
Capacité en mAh/g
Pote
ntiel (V
olts v
s. Li+
/Li)
y in
Voltage fade
? Double fundamental problem Origin of capacity
Origin of drop in voltage
Li[Li0.2Mn0.53Co0.14Ni0.13 ]O2 [3 redox centers]
M. Sathiya et al. , Nature Materials, 12, 827 (2013)
How to simplify this problem ??? a new chemical approach ..
3rd périod
Li2[Ru1-xSnx]O3 [redox center]
4th périod
Layeredstructurepreserved
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
2.0
2.5
3.0
3.5
4.0
4.5
Volt
age
(V v
s. L
i+/
Li0
)
x in LixRu
0.75Sn
0.25O
3
Capacité identique250 mAh/g
Pote
ntie
l (V
olts
vs.
Li+
/Li
)
300 240 180 120 0
Capacité en mAh/g280 210 140 70 0
Capacity in mAh/g
Identical capacity> 260 mAh/g
0.8 1.0 1.2 1.4 1.6
2.0
2.5
3.0
3.5
4.0
4.5
Vol
tage
(V
vs.
Li+ /L
i0 )
x in LixRu
0.5Sn
0.5O
3
2.0 2.5 3.0 3.5 4.0 4.5-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
100th
25th
10th
dx/d
V
Voltage (V vs. Li+/Li
0)
1st
50th
100th
cycles
50th
cycles
10th
cycles
1st
cycle
x in LixRu
0.75Sn
0.25O
3
Chute de potentieltrès limité
200 150 100 50 0
Capacité en mAh/g
Pot
entie
l (V
olts
vs.
Li+ /
Li
)
e
Capacity in mAh/g
Potential fadingNearly canceledn
M. Sathiya, et al. Nature Materials 14, 230–238 (2015)
Origin of the redox activity in Li2Ru0.75Sn0.25O3
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
2.0
2.5
3.0
3.5
4.0
4.5
280 210 140 70
0 Capacity in mAh/g
Cel
l Vol
tage
(V
)
Ru4+Ru5+
(O2)n-
2O--
X-ray photoemission spectroscopy (XPS)
Energiede liaison (eV)
538 536 534 532 530 528 526
XPS Signal(O2)
2
(O2)
X-ray photoemission spectroscopy
Binding energy (eV)
(fully charged sample)
(H2O)
(H2O2)
n-
M. Sathiya et al. , World patent -12197509.8-1359 M. Sathiya et al. , Nature Materials, 12, 827 (2013)
Electron paramagnetic resonance
310 320 330 340 350 360 370
4.6 V
d''/d
B
Champs magnétique [mT]
Signal(O2)
n
RPE
Magnetic field in [mT]
(fully charged sample)
Electron paramagnetic Resonance (EPR)
First direct evidence for an anionic redox process (2O-- (O2)
n-)in Li-rich lamellar compounds
Monitoring redox processes in Li2Ru0.75Sn0.25O2 by operando Electron Paramagnetic Resonance (EPR)
300 320 340 360 380
A
300 320 340 360 380
A
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
300 320 340 360 380
A
d’/d
B
Magnetic field strength
(mT)
d’/dB
Magnetic field strength
(mT)
V V
s. L
i+/L
i0
x in LixRu0.75Sn0.25O3
Ru4+ + O2-
(O2)n- + Ru4+
Ru5+ + O2-
Ru5+
(O2)n-
(O2)n-
Ru5+
4 V
4.6 V
Charge Discharge
M. Sathya, et al. (Nature communications , Février 2015)
5 mm
The exacerbated capacity of Li-rich layered materials is nested in the cumulative cationic and anioinic redox species. Ru4+/5+ (2O-- (O2)
n-)
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s.
Li+/L
i0
a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s. L
i+/L
i0
a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s. L
i+/L
i0 a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
Li foil + plating
Ru+5
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s.
Li+/L
i0
a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
Ru+5 + (O2)n-
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s.
Li+/L
i0
a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
(O2)n-
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
0
-1
-2
1 2-1-2 3
-3
-4
54
-5
3
-2
12
0
-4-3
-1Metallic lithium
Separator
54-5 3-2 1 20-4 -3 -1mm
mm
Al Current collector
Cu Current collector
Li2Ru0.75Sn0.25O3+C
0.4 0.8 1.2 1.6 2.02.0
2.5
3.0
3.5
4.0
4.5
x in LixRu0.75Sn0.25O3
V v
s.
Li+/L
i0
a
d
cb
(a)
(c)(d)
(b)1
0.5
0
1
0.5
0
mm mm
mm
mm
mm mm
mm
mm
O- - + Ru+4
Li foil
M. Sathya, J.B. Leriche, E. Salader, D. Gourrier, H. Vezin and J.M. Tarascon (Nature communications, Fevrier 2015)
Localisation of the cationic/anionic redox species by insitu EPR Imaging: A first
EPR imaging: Key tool for monitoring electrode homogenity and kinetics
What’s going at the atomic scale ? . Can we visualize the O-O dimers ..
Pristine Li2Ru0.75Sn0.25O31 nm
Li
Ru/Sn
Li
Li
Ru/Sn
1 nmOcta.
Cha
rged
til
l 4.6
V
A massive cationic migration
1st Discharge
1 nm
Ru/Sn
Ru/Sn
which is reversible
Visualize the material at the microscopic scale (HAADF-STEM)
M. Sathiya, et al. Nature Materials 14, 230–238 (2015) Collaboration avec A. M. Abakumov et G. Van Tendeloo.
E. McCalla, A. Abrakusov, .. and J.M. Tarascon Science , Décembre 2015
Explore ≠ members of the Li2MnO3 family (M=Ir)
How to prevent this cationic migration ? Play with chemistry
[001]
Z2 Z1/3
(O2)n- c a
b
Pot
entia
l (V
)
x in Li2-xIrO3 O3-type
O1-type
O
Li
Ir
First visualization of (O -O) dimers in Li-rich layered oxide electrodes-
Can we directly measure the (O-O) dimer lengths ?
Use of the D1B Neutron line at ILL (O-O) dimers
2.45 Å
E. McCalla, A. Abakumov, G. Rousse, M.L. Doublet and J.M. Tarascon , Science ; December 2015
Direct evidence for shorter (O-O) bonds in Li-rich layered oxides electrodes
2.4( A°
Rp = 7.7%
Pristine sample (O3)
Charged sample (O1)
Rp = 7.7%
Pristine sample (O3)
Charged sample (O1)
Rp = 7.7%
Pristine sample (O3)
Charged sample (O1) (O-O)
2.84 Å
(O-O) 2.45 Å
Ir
Li
O
LiRhO2
Recent evidence of (O-O) dimers in Li-rich layered oxides: LiRhO2
LiyRh3O6
2.26Å
Pristine LiRhO2
2.82Å
Shortening of the bonds between O belonging to
two ≠ octahedras
D. ikhailova, 0.M. Karakuina, D. Batuk, A. Abrakusov, et al; Inorganic chemistry, July 2016
What abput the origin of
the voltage fade ?
From Sn (4d 10) to Ti(3d0) substitute
Li2CO3+ 0.75RuO2 + 0.25TiO2 Li2Ru0.75Ti0.25O3
800° C
Ball mill + 24 hours at 800°C
Studying the Li2Ru0.75Ti0.25O3 system
0.5 1.0 1.5 2.0
2.0
2.5
3.0
3.5
4.0
4.5
Volt
age (
V v
s. L
i+/L
i0)
x in LixRu0.75Ti0.25O3
Cap
acit
y(m
Ah
/g)
Cycle number0 20 40 60 80
0
50
100
150
200
Ti+4, seems to be the worst substitute ..
Capacity/cycling
0.4 0.6 0.8 1.0 1.2 1.41.5
2.0
2.5
3.0
3.5
4.0
4.5
Vo
ltag
e (
V v
s. L
i+/L
i0)
x in LixRu
0.75Ti
0.25O
3
80 1
x in LixRu0.75Ti0.25O3
Vo
ltag
e (V
vs.
Li+
/Li0
)
0.7 V
Voltage fade
M. Sathya, A.M. Abakumov, K. Ramesha, D. Foix, G. Rousse, and J.M. Tarascon, Nature Materials (2015)
Li2Ru0.75Sn0.25O3
100 Cycles
Octa
Octa
100 Cycles
Suppression of the potential fade upon cycling by Tin: Why ?
50 Cycles
Octa
Li2Ru0.75Ti0.25O3
Cations trapped in tetrahedral sites
2
tetra
tetra
M. Sathya, A.M. Abakumov, K. Ramesha, D. Foix, G. Rousse, and J.M. Tarascon, Nature Materials 1er Décembre 2014
Provide chemical clues to enable the development of Li-rich NMC for the next generation of Li-ion batteries
Voltage fade upon cycling is linked to the capturing of
small cations ions in tetrahedral sites <
0.6 Å 0.69 Å
Ti4+ Sn4+
From modem materials to
Li-rich NMC
surface
deposits
On–
O 1s
O2–
O 1s
surface
deposits
On–
O2–
O 1s
surface
deposits
On–
O2–
O 1s
surface
deposits
On–
O2–
1st
cycle
0 100 200 300
0
10
20
30
2nd
cycle
0 100 200 300
0
10
20
30
b
2nd c
ha
rge
1st d
isch
arg
e
a 1st cycle at 6.9 keV
1st c
ha
rge
3.25 V
3.60 V
4.10 V
4.46 V
Pristine
4.80 V
2.00 V
sat.
537 535 533 531 529 527
Binding energy (eV)
2nd
cycle at 6.9 keV
3.25 V
3.60 V
4.10 V
4.25 V
3.75 V
4.80 V
2.00 V
sat.
537 535 533 531 529 527
Binding energy (eV)
1.487 keV
6.9 keV
bu
lksu
rfa
ce
c 1st charged, 4.80 V
3.0 keV
34%
34%
537 535 533 531 529 527
33%sat.
Binding energy (eV)
d 1st discharged, 2.00 V
su
rfa
ce
bu
lk
1.487 keV
6.9 keV
3.0 keV
10%
9%
537 535 533 531 529 527
9%
2nd d
isch
arg
e
Binding energy (eV)
2.00 V 3.25 V
3.60 V
4.80 V
4.10 V
Pristine
3.0 keV disch. 6.9 keV disch. 3.0 keV charge 6.9 keV charge
% O
n– / (
On– +
O2–)
Capacity (mAh.g-1)
4.46 V
e f 3.0 keV disch. 6.9 keV disch. 3.0 keV charge 6.9 keV charge
Capacity (mAh.g-1)
% O
n– / (
On– +
O2–)
2.00 V3.25 V
3.60 V
4.10 V
4.80 V
4.25 V
3.75 V
surface
deposits
On–
O 1s
O2–
O 1s
surface
deposits
On–
O2–
O 1s
surface
deposits
On–
O2–
O 1s
surface
deposits
On–
O2–
1st
cycle
0 100 200 300
0
10
20
30
2nd
cycle
0 100 200 300
0
10
20
30
b
2nd c
ha
rge
1st d
isch
arg
ea 1
st cycle at 6.9 keV
1st c
ha
rge
3.25 V
3.60 V
4.10 V
4.46 V
Pristine
4.80 V
2.00 V
sat.
537 535 533 531 529 527
Binding energy (eV)
2nd
cycle at 6.9 keV
3.25 V
3.60 V
4.10 V
4.25 V
3.75 V
4.80 V
2.00 V
sat.
537 535 533 531 529 527
Binding energy (eV)
1.487 keV
6.9 keV
bu
lksu
rfa
ce
c 1st charged, 4.80 V
3.0 keV
34%
34%
537 535 533 531 529 527
33%sat.
Binding energy (eV)
d 1st discharged, 2.00 V
su
rfa
ce
bu
lk
1.487 keV
6.9 keV
3.0 keV
10%
9%
537 535 533 531 529 527
9%
2nd d
isch
arg
e
Binding energy (eV)
2.00 V 3.25 V
3.60 V
4.80 V
4.10 V
Pristine
3.0 keV disch. 6.9 keV disch. 3.0 keV charge 6.9 keV charge
% O
n– / (
On– +
O2–)
Capacity (mAh.g-1)
4.46 V
e f 3.0 keV disch. 6.9 keV disch. 3.0 keV charge 6.9 keV charge
Capacity (mAh.g-1)
% O
n– / (
On– +
O2–)
2.00 V3.25 V
3.60 V
4.10 V
4.80 V
4.25 V
3.75 V
Li-rich NMC
What are the cationic / anionic redox potentials ?
Direct evidence of bulk anionic redox
Anionic redox in Li-rich NMC –via bulk-sensitive hard-XPS
From model compounds to Li-Rich Li1.2Ni0.14Mn0.54Co0.13O2 : What’s the story?
A.S Gaurav et al; (Submitted 2017)
The science underlying the
anionic redox process
The source of controversial debates (need to go back to basics)
Some basic recalls ….
MO6
Metal (M) Ligand (O)
s
4p
4s
3d
eg
a1g
eg
a1g*
t1U
*
t1U*
*
pt2g
t2g*
Metal (M) Ligand (O)
From Molecular Orbitals to the Band Structure
O
M S2/D
S2/D
D
MO*
MO
M
O
MO*
MO
M
O
D
S2/D
S2/D
Ionic bond Covalent bond
Increasing O
character
Increasing M
character≈ 100% O character
≈ 100% M character
Energy difference MO/MO* given by D + 2S2/D
The iono-covalence: Its influence on band positions
Y. Xie, M. Saubanère, M.-L. Doublet, Energy Environ. Sci. 10 (2017)
How this can happen ? What is the underpinning science …
O
𝐸
(M-O)
(M-O)*
O(2𝑝)
non
bonding
O(2𝑠)
D
U
𝐿𝑖𝑀𝑂2 𝐿𝑖2𝑀𝑂3 , Li(Li1/3Mn2/3)O2
O2
O2
𝐸
(M-O)
(M-O)*
O(2𝑠)
Classical situation: 1 Redox band An illicit situation: 2 Redox bands
D.-H. Seo, G. Ceder et al. Nature Chemistry (2016).
Anionic redox depends upon the competition between U and D
30
Pearce, Tarascon et al, Nature Mater. (2017)
U
v M
O
E
MO*
MO
Cationic redox (One band)
D
e–
D ∼ U/2 D << U U << D
U
E
D
e– + e-
Anionic redox (two bands) Extra capacity
Octahedral distorsion
Short O-O bonds
Pristine Charged
(O2)n-
Saubanère, Tarascon et al, EES 9 (2016)
U
D
E
e–
Anionic redox (One band but irreversible)
O2– O22–
release
P. Bruce, Nature chemistry (2016)
Li2MO3
More Li ?
Increase the O/M ratio
To which extreme can we push the capacity using the anionic redox concept?
A. Perez et al. Submitted
New Li3IrO4
phase
Ir + 1.5 Li2CO3
Li3IrO4
950°C, 24h
Air
DisorderedLi2Ir planes
Pure Li planes
DisorderedLi2Ir planes
Li3IrO4
New phase:
Li3IrO4 or Li(Li1/2Ir1/2)O2
5 10 15 20 25 30 35 40
2 (°, = 0.414 Å)
10 30 50 70 90 110
2 (°, = 1.544 Å)
O2
O2
Li3MO4
0 1 2 3 4 5
1
2
3
4
5
V v
s L
i+/L
i
x in LixIrO4
Limit the
charge at x = 1
A. Perez et al. submitted
x in LixIrO4
Electrochemical performance of Li3IrO4 vs. Li+/Li while monitoring pressure
Pressure sensor
Cell
Mass Spect.
O2-/(O2)n-
3.5 e- are exchanged by transition metal ….
(340 mAh/g) Li1IrO4 Li4.5IrO4
Increasing the O/M ratio: a trade-off would have to be found between extra-capacity and structural stability
Highest value ever reported for insertion cathode materials in Li-ion batteries
𝑛𝑑-shell : M-O covalence is to stabilize the network
Network stability w.r.t O2 release
𝐿𝑖𝑥𝑀𝑂3 → 𝐿𝑖𝑥𝑀𝑂3−𝛿 + 𝛿 2 𝑂2
Xie et al. Energy & Environ. Sci. Asap 2016
Positive enthalpy => formation of O2 vacancies is not favorable
(O2)n- stability against recombination into O2 :
a DFT approach
Ti V Cr Mn Fe Co Ni
Zr Nb Mo Tc Ru Rh Pd
Hf Ta W Re Os Ir Pt
Rea
cti
on
en
tha
lpy
(eV
/FU
)
configuration in
zone
3d
4d
5d
Exploit such findings to design Li2MM O3 phases stable against (O2)n- recombination
,
Li-content : all 𝑀(3𝑑)-based materials are unstable w.r.t. O2 release
once the first Li is removed
! … Bad news for applications
Therefore 5d metals with n> 3 are stable in agreement with the use of Ir
The Li3MO4 family: a rich crystal chemistry
34
Li3NbySb1-yO4
Creation of a platform for identifying key indicators to manipulate anionic redox
J. Quentin et al. Chemistry of materials 2017 Yabuuchi et al, PNAS 112 (2015)
Li3RuO4
Li3NbO4 Li3SbO4
Li3MO4 phases
Effect of dimensionality: is anionic
redox limited to 2D compounds ?
Effect of modifying the crystal structure on the anionic redox reactivity
Layered rocksalt structures as a funstion of increasing Li/M ratio. NaCl structure
F m -3 m
dense ABCABC oxygen
stacking
Li3NbO4
I -4 3 m
Nb
Li
Li4MoO5
P -1
Mo
Li
LiMO2
R -3 m
M
Li
M
Li
M
Li2MO3
C 2/m
LiM2
LiM2
LiM2
Li
Li
3D 2D Increases disorder
Disordered
phases
x in Li1.3-xNb0.3Mn0.4O2 x in Li1.2-xTi0.4Mn0.4O2
Yabuchi et al; PNAS, 2016
Is the anionic redox process only limited to 2D layered compounds ?:
IrO2 + Li2CO3 (10% excess) < 950°C (24h) α-Li2IrO3 2D structure
IrO2 + Li2CO3 (10% excess) β-Li2IrO3 > 1050°C ( > 90h)
LiIr2
Li3
Li2Ir
Li2Ir
3D structure
100 µm
1st cycle
2ndcycle
3rd cycle
1st cycle
2ndcycle
5th cycle
10th cycle
Electrochemical performance of the 3D Li-rich polymorph
All Li can be removed "IrO3"
Neutron Powder diffraction + ABF-STEM
4 V - charged -LiIrO3
<Ir-O> = 1.972 ÅO-O distortion D (x104)= 25.2
X-ray photoemissionAnionic + cationic
(~ 2 e- per Ir)
Anionic redox activity is not solely limited to 2D systems: its implementation to 3D
oxides opens wide the research field for high capacity electrodes
P. Pearce et al. Nature materials February 2017
Anionic redox – A transformational approach to design high energy cathodes
500
Wh kg–1
Classical Layered OxidesLiMO2
cationic redox only
Li-rich Layered Oxides
Li1+yM1–yO2
combined cationic
+ anionic redox
1000
Wh kg–1
Can we use Li-rich cathodes in real-world
batteries… Any practical roadblocks ???
Poor kinetics
Hysteresis
Voltage decay
2.0 2.5 3.0 3.5 4.0
dQ
/ d
V
Voltage (V)
Cationic redox
Anionic redox
Summation
Deconvolution via operando XAS
2.0 2.5 3.0 3.5 4.0 4.5
C/10
C/2.5
C/5
dQ
/ d
V
Voltage (V)
Ru4+/5+peak O2–/On– peak
G. Assat, J-M. Tarascon et al., J. Electrochem. Soc., (2016).
Poor kinetics of Li-rich NMC: (Li2Ru0.75Sn0.25O3)
Anionic redox shows sluggish
kinetics and triggers hysteresis
Consequences of poor kinetics/large polarisation: Energy efficiency ….
Poor round-trip energy efficiency in LR-NMC:_Role of anionic redox
G. Assat, J-M. Tarascon et al., J. Electrochem. Soc., (2016).
Are these practical issues surmountable ?
Sathya, Tarascon et al. , Nature Materials 2015 ,vol. 14, no. 2, pp. 230–8
A promising direction being pursued
Design of materials within which cationic and anionic redox occur at the same
potential
Practical roadblocks in Li-rich cathodes and their consequences 300 200 100 0
Capacité en mAh/g
Pote
ntie
l (V
olts
vs.
Li+
/Li
)
0.0 0.2 0.4 0.6 0.8 1.0
2.0
2.5
3.0
3.5
4.0
4.5
050100150200250
4.0
4.5
3.5
3.0
2.5
5.0
Capacité en mAh/g
Pote
ntie
l (V
olts
vs.
Li+
/Li)
y in
y in
Voltagefade
Exacerbatedcapacity
(> 280 mAh/g)
1st
100th
Capacity in mAh/g
Voltage decay
2.0 2.5 3.0 3.5 4.0 4.5
C/5
dQ
/ d
V
Voltage (V)
Ru4+/5+peak O2–/On– peak
Poor kinetics
Voltage (V)
dQ/d
V
2.0 2.5 3.0 3.5 4.0 4.5
C/10
C/2.5
C/5
dQ
/ d
V
Voltage (V)
G. Assat, J-M. Tarascon et al., J. Electrochem. Soc., (2016).
Importance of substituent
(chemical elements with large ionic radii)
Td
M. Freire et al. Nature materials Novembre 2015
Importancy of anionic redox beyond electrode materials
N. Yabuushi et al. PNAS May 2015 A. Grimaud, ,,, Tarascon Nature materials 15 (2016)
New perovskites with
tailored O-O bonds
44
http://www.college-de-france.fr/site/en-college/index.htm
Acknowledgments