quantitative electron diffraction tomography for the structure solution of cathode materials for...

Quantitative electron diffraction tomography for

the structure solution of cathode materials for

Li-ion batteries Olesia Karakulina, Daria Mikhailova, Vasiliy Sumanov, Dmitry Batuk, Oleg Drozhzhin, Nellie Khasanova, Evgeny Antipov, Artem Abakumov, Joke Hadermann

http://www.slideshare.net/OlesyaKarakulina

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Outline

1. Li-ion batteries

2. Cathode materials

– Problems

– Structure determination methods

3. Li detection and content estimation

– LixMn0.5Fe0.5PO4

4. Structure solution of unknown oxide

having low symmetry

– LixRhO2

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1. Li batteries. Charge.

4

1. Li batteries. Discharge.

5

2. Cathode materials. Problems

Common problems

The charged phase is

more energy stable

than pristine.

The channels are

blocked by transition

metal atoms.

operation time decrease

capacity decay 1. pristine phase

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2. Cathode materials. Problems

Common problems

The charged phase is

more energy stable

than pristine.

The channels are

blocked by transition

metal atoms.

operation time decrease

capacity decay 1. pristine phase

2. charged phase

7

2. Cathode materials. Problems

Common problems

The charged phase is

more energy stable

than pristine.

The channels are

blocked by transition

metal atoms.

operation time decrease

capacity decay 1. pristine phase

2. charged phase

3. discharged phase

8

2. Cathode materials. Crystal structure determination

Powder

X-ray

diffraction

Bulk

- low sensitivity to Li

- poor quality of powder

diffraction pattern

Bulk

+ sensitive to Li

- necessary amount of

sample>1g

Powder

neutron

diffraction

Electron

diffraction

tomography

Single crystal

+ sensitive to Li

+ necessary amount of

sample <1 mg

- 1D projection of

3D reciprocal space

+ 3D reconstructions of

3D reciprocal space

Ab-initio structure

determination

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3. LixMn0.5Fe0.5PO4

LiMn0.5Fe0.5PO4 Mn0.5Fe0.5PO4 Li0.5Mn0.5Fe0.5PO4

-0.5Li+ -0.5Li+

+2 +2 +2 +3 +3 +3

O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

Fe+2 Fe+3

Mn+2 Mn+3

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3. LixMn0.5Fe0.5PO4

O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

In-situ XRD in an electrochemical test cell

Fe+2 Fe+3

Mn+2 Mn+3

LiMn0.5Fe0.5PO4 Mn0.5Fe0.5PO4 Li0.5Mn0.5Fe0.5PO4

-0.5Li+ -0.5Li+

+2 +2 +2 +3 +3 +3

211 020

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3. LixMn0.5Fe0.5PO4

O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

TEM Pristine LiMn0.5Fe0.5PO4

Space group: Pnma

Half-charged Li0.5Mn0.5Fe0.5PO4

Extinction symbol: Pna

Fully-charged Mn0.5Fe0.5PO4

Extinction symbol: Pna

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3. LixMn0.5Fe0.5PO4

Object: 1 crystal

Process: tilting and taking electron diffraction patterns with 1

degree step

Electron diffraction tomography

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3. LixMn0.5Fe0.5PO4

O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

STEP 1. Structure solution without prior knowledge

1. Fe, P and O atoms were detected by charge flipping algorithm

2. Li was located using difference Fourier maps

RF=0.198

STEP 2. Refinement

• Refined model is in agreement with experimental data • EDT results are close to XRD ones

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O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

Difference Fourier map (Fobs-Fcalc) ‘Mn0.5Fe0.5PO4’ model

LiMn0.5Fe0.5PO4

Mn0.5Fe0.5PO4

3. LixMn0.5Fe0.5PO4

Li detection

• Fourier maps show electrostatic potential in the cell

Experimental Fourier map

Calculated Fourier map

Difference Fourier map

Li, Mn, Fe, P, O Mn, Fe, P, O Li = -

Li

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3. LixMn0.5Fe0.5PO4

O.A. Drozhzhin, et al. Electrochimica Acta, 191, 149–157 (2016).

• Li occupancy was refined • Values correspond to those

calculated from electrochemical curves

Theory: MO6 should has Jahn-Teller distortion

due to Mn+2 Mn+3

Practice: MO6 is slightly distorted

Jahn-Teller distortion • is not cooperative • results in local structure distortion

c

Mn0.5Fe0.5PO4 +3 +3

LiMn0.5Fe0.5PO4 +2 +2

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4. LiXRhO2

In-situ synchrotron powder diffraction in electrochemical test cells

LiRhO2 Li0.55RhO2 LixRhO2

charge

-0.45 Li+

charge 4.1 V 3.85 V

D. Mikhailova, et al. Inorg. Chem., 55 (14), 7079–7089, (2016)

-~0.45 Li+

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4. LiXRhO2

In-situ synchrotron powder diffraction in electrochemical test cells

LiRhO2 Li0.55RhO2 LixRhO2

charge

-0.45 Li+

charge

-~0.45 Li+

4.1 V 3.85 V

D. Mikhailova, et al. Inorg. Chem., 55 (14), 7079–7089, (2016)

NEW PHASE

?

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4. LiXRhO2

Applied techniques: • SAED and electron diffraction

tomography • Monte Carlo method for

optimization of Li positions

C2/m Rf = 0.268 a=14.188(2) Å b=3.0740(2) Å c=4.5050(7) Å β=92.087(8)o

D. Mikhailova, et al. Inorg. Chem., 55 (14), 7079–7089, (2016)

Structure solution: 3D structure with 2 channel types

ramsdellite 2x1 channel

rutile 1x1 channel

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4. LiXRhO2

D. Mikhailova, et al. Inorg. Chem., 55 (14), 7079–7089, (2016)

From layered to 3D structure: possible mechanism

c

Oxygens are partially oxidized

1. Shot-range rearrangement 2. Formation of short O-O bond (<2.8 Å)

2.26 Å

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4. LiXRhO2

1. Partially reversible transformation 3D 2D

2. 3D structure hosts extra 20% Li in rutile channels

D. Mikhailova, et al. Inorg. Chem., 55 (14), 7079–7089, (2016)

discharge

+ Li+

Lithiation of 3D structure

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Conclusions

1. Electron diffraction tomography allows to define the positions of Li

atoms and refine their occupancy.

2. Jahn-Teller effect in Mn0.5Fe0.5PO4 results in local structure distortion. In comparison with analogous compounds containing more Mn, the distortion is insignificant.

3. The behavior of LiRhO2 upon charge and discharge differ from isostructural and isoelectronic LiCoO2. – Layered structure transforms to 3D structure upon charge. – 3D structure partially transforms back to the layered one upon discharge. – 3D structure hosts Li in ramsdellite and rutile channels

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Acknowledgement

Promoters: Prof. Joke Hadermann Prof. Artem Abakumov Dr. Dmitry Batuk

Collaborators: V. Sumanov Dr. O. Drozhzhin Dr. E. Antipov Dr. D. Mikhailova

Max Planck Institute for

Chemical Physics of Solids

Dresden, Germany

Moscow State University

Moscow, Russia

Financial support: • FWO grant G040116N

• EMS-EMC 2016 scholarship

Research Fund - Flanders

European Microscopy Society

University of Antwerp,

Antwerp, Belgium

Electron microscopy for

materials science