ELECTROCHEMISTRY AND ELECTROCHEMICAL ´723,&$/352%...

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

http://www.college-de-france.fr/default/EN/all/college/








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


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



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


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



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


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



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


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



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


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



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


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%


Charged sample (O1)

Rp = 7.7%


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


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)


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


Acknowledgments








ELECTROCHEMISTRY AND ELECTROCHEMICAL ´723,&$/352%...

Documents

Transcript of ELECTROCHEMISTRY AND ELECTROCHEMICAL ´723,&$/352%...