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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
2
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
3
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
6
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
?
18
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
22
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