combining li-excess and reversible oxygen charge transfer...
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Combining Li-Excess and Reversible Oxygen Charge Transfer to Achieve High Capacity Cathodes
Alexander Urban, Jinhyuk Lee, Dong-Hwa Seo,
Xin Li, Aziz Abdellahi, and Gerbrand Ceder
Department of Materials Science and Engineering,
University of California, Berkeley.
aurban@berkeley.edu
Phoenix, AZ, April 20, 2017
Download these slides at http://ceder.berkeley.edu
Towards cathode materials with greater energy density
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 2
Amount of electrons (= Li) per mass or volume that can utilized
Voltage
Potential difference between electrodes.
Capacity
Cathode material (positive electrode) is the bottleneck for capacity & voltage in LIBs.
Capacity × Voltage = Energy Density
Highest energy density cathodes are layered, but further improvement hard with layered structure
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 3
O3-type layered LiCoO2-structure
O TM
Li
LCO (Co) NCA (Ni, Co, Al) NCM (Ni, Co, Mn)
Limited chemistry: Co, Ni, Mn, Al (no TM migration)
Cannot utilize entire Li content
Limited capacity: 140-200 mAh/g
Need greater capacity for higher energy density
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 4
Data from: Nitta et al., Materials Today 18 (2015) 252-264.
Greater specific capacities
needed
Energy Density (Wh/kg)
Cation-Disordered Cathode Materials for Li-Ion Batteries
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 5
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 6
layered O3
disordered rocksalt
J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Science 343 (2014) 519-522.
Li1.211Mo0.467Cr0.3O2 (LMCO) forms in layered structure but becomes cation disordered when cycled
well-separated Li and TM layers
intense cation mixing
Cation-disordered LMCO has a remarkable capacity
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 7
1 Li per LiMO2
J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Science 343 (2014) 519-522.
~1 Li atom per LiMO2 formula unit can be reversibly cycled
LiCoO2
Fast (low-barrier) 0-TM channel
Cation-disorder creates fast 0-TM diffusion channels that do not exist in stoichiometric layered materials
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 8
0-TM
1+
1+
2-TM
3+
3+
1-TM
1+
3+
? ?
Cation disordered
Layered
Excess Li needed to increase 0-TM channel concentration
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 9
The 0-TM channel concentration is just 6% in the stoichiometric LiMO2
Small concentration of 0-TM channels
0-TM channels =
Locally Li-rich environment
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 10
Layered
Disordered
Percolation threshold
A. Urban, J. Lee, and G. Ceder, Adv. Energy Mater. 4 (2014) 1400478.
One Li 0-TM cyclable at
~25 % Li excess
Li1.211Mo0.467Cr0.3O2
Around 10% Li excess enables 0-TM percolation in cation disordered structures
0-TM
Impact on Li-ion battery cathode research 1991: Li3V2O5 = Li1.2V0.8O2
C. Delmas, S. Brèthes and M. Ménétrier ω-LixV2O5, J. Power Sources 34 (1991) 113-118.
1998: LiMO2 (M=Ti, Mn, Fe, Co, Ni) by mechanochemical synthesis (ball-milling)
M. Obrovac, O. Mao, and J. Dahn, Solid State Ionics 112 (1998) 9-19.
2014: Li1.211Mo0.467Cr0.3O2
J. Lee, A. Urban, X. Li, D. Su, G. Hautier, and G. Ceder, Science 343 (2014) 519-522.
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 11
2015: Li2VO2F = Li1.333V0.666O1.333F0.666
R. Chen, S. Ren, M. Knapp, D. Wang, R. Witter, M. Fichtner, and H. Hahn, Adv. Energy Mater. 5 (2015) 1401814.
2015: Li1.3NbxM0.7-xO2 (M = Mn, Fe, Co, Ni)
N. Yabuuchi, M. Takeuchi, M. Nakayama, H. Shiiba, M. Ogawa, K. Nakayama, T. Ohta, D. Endo, T. Ozaki, T. Inamasu, K.
Sato, and S. Komaba, Proc. Natl. Acad. Sci. USA 112 (2015) 7650–7655.
2015: Li1.25Nb0.25Mn0.5O2
R. Wang, X. Li, L. Liu, J. Lee, D.-H. Seo, S.-H. Bo, A. Urban, G. Ceder, Electrochem. Commun. 60 (2015) 70–73.
2015: Li1.2Ni0.333Ti0.333Mo0.133O2
J. Lee, D.-H. Seo, M. Balasubramanian, N. Twu, X. Li and G. Ceder, Energy Environ. Sci. 8 (2015) 3255–3265.
2015: Li1+xTi2xFe1-3xO2
S. L. Glazier, J. Li, J. Zhou, T. Bond and J. R. Dahn, Chem. Mater. 27 (2015) 7751–7756.
2016: Li1.333Ni0.333Mo0.333O2
N. Yabuuchi, Y. Tahara, S. Komaba, S. Kitada and Y. Kajiya, Chem. Mater. 28 (2016) 416-419.
2016: Li1.3Nb0.3V0.4O2
N. Yabuuchi, M. Takeuchi, S. Komaba, S. Ichikawa, T. Ozaki, and T. Inamasu, Chem. Commun. 52 (2016) 2051-2054.
The new materials have high energy densities
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 12
LCO, NMC, NCA data from: Nitta et al., Materials Today 18 (2015) 252-264.
Energy Density (Wh/kg)
The chemical space for disordered cathodes is much larger than for layered materials
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 13
Abundance data from: www.webelements.com (3/2017)
A new opportunity space for Co-free cathodes
Cation disorder is beneficial
Cation mixing does not affect practical capacity for compositions with more than 15% Li excess
Increased structural stability when delithiated enables very high capacities
Much larger chemical space
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 14
A. Urban, J. Lee, and G. Ceder, Adv. Energy Mater. 4 (2014) 1400478.
J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Science 343 (2014) 519-522.
Capacity
Understanding the effect of cation disorder
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 15
Understood conditions for high reversible capacities in DO-LiTMO2
Voltage
How does cation disorder affect the voltage?
Can disordered materials achieve high voltages?
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 16
LCO, NMC, NCA data from: Nitta et al., Materials Today 18 (2015) 252-264.
Higher voltage desirable
Energy Density (Wh/kg)
Cation disorder can raise or reduce the voltage
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 17
A. Abdellahi†, A. Urban†, S. Dacek, and G. Ceder, Chem. Mater. 28 (2016) 5659-3665.
Cation disorder does not necessarily lead to low voltages
Slope of voltage profiles depends on TM species
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 18
Vo
ltag
e (
V)
A. Abdellahi, A. Urban, S. Dacek, and G. Ceder, Chem. Mater. 28 (2016) 5373-5383.
Small slope for High-V TMs
Extra capacity beyond TM redox: oxygen redox enables very high capacity Li-excess cathodes
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 19
J. Lee, G. Ceder et al., Energy Environ. Sci. 8 (2015) 3255–3265.
N. Yabuuchi et al., PNAS 112 (2015) 7650.
R. Wang, G. Ceder et al., Electrochem. Commun. 60 (2015) 70–73.
First observed in layered Li-excess materials
Very common in cation disordered cathodes
Li1.2Ni1/3Ti1/3Mo2/15O2
O redox Mn redox
Clear change of oxygen K edge from oxygen redox
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 20
R. Wang, G. Ceder et al., Electrochem. Commun. 60 (2015) 70–73.
Relationship of cation disorder and oxygen redox
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 21
• What is the origin of oxygen redox?
• When does oxygen redox provide extra capacity beyond TM redox?
• Are cation-disordered materials more likely to exhibit O redox?
Origin of Oxygen Redox Activity
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 22
Conventional view: TM redox originates from antibonding M-O state
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 23
M orbital
O orbital
bonding “O ” state
antibonding “M ” state
e- Energy
regular redox state
M orbital
O orbital
bonding “O ” state
Contribution from oxygen 2p
regular redox state
e-
TM redox also exhibits some O contribution but that does not affect the capacity
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 24
Energy
Ceder et al., Nature 392 (1998) 694.
Extra capacity = utilize electrons from bonding states
Strong M-O covalency impedes oxygen redox
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 25
Energy
M orbital
O orbital
M orbital
O orbital
More Covalent Less Covalent
Bonding state lowered Electron is stabilized
Stoichiometric layered materials possess only hybridized (covalent) oxygen states
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 26
three Li-O-M e.g., stoichiometric layered Li-M oxides
M b
and
s O
ban
ds
LiMO2
Li-O-M
t1u*
a1g*
eg*
t2g
t1ub
E
egb
a1gb
DH. Seo†, J. Lee†, A. Urban, R. Malik, SY. Kang, and G. Ceder, Nat. Chem. 8 (2016) 692-697.
Lithium excess/cation disorder creates Li-O-Li configurations with unhybridized O states
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 27
one Li-O-Li, two Li-O-M e.g., Li-excess layered/cation-disordered
Li-M oxides
M b
and
s O
ban
ds
e.g., Li(Li1/3M2/3)O2
Li-O-Li
Li-O-Li
t1u*
a1g*
eg*
t2g
t1ub
E
egb
a1gb
DH. Seo†, J. Lee†, A. Urban, R. Malik, SY. Kang, and G. Ceder, Nat. Chem. 8 (2016) 692-697.
Lithium excess/cation disorder creates Li-O-Li configurations with unhybridized O states
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 28
DH. Seo†, J. Lee†, A. Urban, R. Malik, SY. Kang, and G. Ceder, Nat. Chem. 8 (2016) 692-697.
M b
and
s O
ban
ds
e.g., Li(Li1/3M2/3)O2
Li-O-Li
t1u*
a1g*
eg*
t2g
t1ub
E
egb
a1gb
M orbital
O orbital
bonding O state
anti-bonding M state
unhybridized state (Li-O-Li)
Accurate first-principles electron densities confirm the Li-O-Li mechanism
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 29
DH. Seo†, J. Lee†, A. Urban, R. Malik, SY. Kang, and G. Ceder, Nat. Chem. 8 (2016) 692-697.
4 Li and 2 Ni 3 Li and 3 Ni 2 Li and 4 Ni
Electron localized along Li-O-Li configuration
1 e- per LiNiO2
Yellow iso-surface: electron density
The labile electron along the Li-O-Li configuration becomes redox accessible. Same mechanism for: Li(Ni,Mn)O2, Li(Ru,Sn)O2, Li(Ni,Ti,Mo)O2, Li(Mn,Nb)O2
Cation disorder & Li excess promote oxygen redox participation by creating Li-O-Li
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 30
Li
M M M
Li Li
O
Stoichiometric layered Li-M oxides (LiMO2)
Li Li Li
M M M
O
Li
Li
Li Li
M M
O
Li-excess layered Li-M oxides (Li1.2M0.8O2)
Li Li
Li Li
Li
Li
Li Li M
M M
O O
Li
Li
Li Li
M M
O
Li Li
Li
M
M M
O
Li Li Li
Li Li M
M M M M M M
O O
Li-excess cation-disordered Li-M oxides (Li1.2M0.8O2)
Li
Statistically, at 15% Li excess every O atom in a cation disordered structure is part of an Li-O-Li bond
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 31
Probability of any O to be part of Li-O-Li
x in Li1+xM1-xO2
Explains high O redox activity in cation disordered cathodes
Summary
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 32
High capacity through cation disorder
• Cation disorder creates new type of fast 0-TM Li diffusion channel
• 15% Li excess enables 0-TM Li percolation
• Affects average voltage, voltage slope, and redox mechanism
Extra capacity from oxygen redox
• Oxygen redox originates from labile non-bonding oxygen states created by Li-O-Li configurations
• Increased O-M covalency does not result in extra capacity
• Li excess and cation disorder promote oxygen redox
Lee, Urban, Ceder et al., Science 343 (2014) 519-522.
Urban, Lee, Ceder, Adv. Energy Mater. 4 (2014) 1400478.
Abdellahi†, Urban†, Dacek, Ceder, Chem. Mater. 28 (2016) 5659-3665.
Abdellahi, Urban, Dacek, Ceder, Chem. Mater. 28 (2016) 5373-5383.
Seo†, Lee†, Urban, Ceder et al., Nat. Chem. 8 (2016) 692-697. Seo, Urban, Ceder, Phys. Rev. B 92 (2015) 115118.
Acknowledgments
Apr. 20, 2017 Alex Urban - MRS Spring Meeting 33
Jinhyuk Lee Xin Li (now Harvard U)
Aziz Abdellahi (now at A123)
Gerd Ceder Dong-Hwa Seo
Ceder Group 2016
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