Solid-state electrolytes exhibit good safety and stability, and are promising to replace current organic liquid electrolytes in rechargeable battery applications. In this talk, we will present our efforts at developing scalable first principles techniques to design novel solid-state electrolytes. Using the recently discovered Li10GeP2S12 lithium super ionic conductor as an example, we will discuss how various properties of interest in a solid-state electrolyte can be predicted using first principles calculations. We will show how the application of these first principles techniques has suggested two chemical modifications, Li10SiP2S12 and Li10SnP2S12, that retains the excellent Li+ conductivity of Li10GeP2S12 at a significantly reduced cost. These modifications have recently been synthesized, and the measured Li+ conductivities are in excellent agreement with our first principles predictions. We will conclude with a demonstration of how relatively expensive first principles calculations can be intelligently scaled and combined with topological analysis to be a useful screening tool for novel solid-state electrolytes.
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First principles design of lithium superionic conductors
1. materiaIs
virtuaLab
First Principles Design of Lithium
Superionic Conductors
Shyue Ping Ong,Yifei Mo, William Davidson
Richards, Lincoln Miara, Hyo Sug Lee, Gerbrand
Ceder
Aug 12, 2014
ACS 248th National Meeting
2. Outline
Introduction to Lithium Superionic Conductors
First Principles Optimization of State of the Art
Superionic conductor
• Li10GeP2S12
• Li7La3Zr2O12
Concept for High-throughput Superionic Conductor
Design
Aug 12, 2014 ACS 248th National Meeting
3. Current organic electrolytes have two
severe limitations
Ethylene carbonate Dimethyl carbonate
Two key limitations
1) Flammability
2) Electrochemical windows < 4.5V
• Limits choice of electrode and
achievable energy densities
A lithium superionic
conductor solid electrolyte
can potentially address both
issues.
NTSB report, March 7 2013
Aug 12, 2014 ACS 248th National Meeting
4. State-of-the-art lithium superionic conductors
Garnet Li7La3Zr2O12 (LLZO)Thio-lisicon Li10GeP2S12 (LGPS)
N. Kamaya et al., Nat. Mater. 2011, 10,
682-686
R. Murugan, et al.,Angew. Chem., Int.
Ed. 2007, 46, 7778−81.
Aug 12, 2014 ACS 248th National Meeting
5. State-of-the-art lithium superionic conductors
N. Kamaya et al., Nat. Mater. 2011, 10,
682-686
R. Murugan, et al.,Angew. Chem., Int.
Ed. 2007, 46, 7778−81.
LGPS
One of the highest Li+ cond.
of 12 mS/cm
Reported electrochemical
window of > 5V
Ge is expensive
Sulfide chemistry is air and
moisture sensitive
LLZO
Oxide chemistry is air stable
Stable against Li?
Low grain boundary
resistance
Lower Li+ cond. of ~0.1 mS/
cm
Aug 12, 2014 ACS 248th National Meeting
6. First principles materials property prediction
What makes a good ionic conductor?
Stability
• Phase stability
• Electrochemical
stability
Diffusivity
• High conductivity
@ 300K
Materials
• Handling / air
sensitivity
• Cost
Phase diagrams MD simulations
Element
substitutions
Aug 12, 2014 ACS 248th National Meeting
7. Ab initio
modeling of
LGPS diffusivity
DFT molecular
dynamics simulation
Self-diffusivity
calculated from
simulated Li+ ion
motion
Y. Mo, S. P. Ong, G. Ceder, First principles study of the
Li10GeP2S12 lithium super ionic conductor material.
Chem. Mater. 2012, 24 15-17
Lithium motion in LGPS
(P/GeS4 tetrahedra frozen for clarity)
Aug 12, 2014 ACS 248th National Meeting
8. Excellent agreement between ab initio diffusivity
and experiments
1 S. P. OngY. Mo,W. Richards, L. Miara, H. S. Lee, G. Ceder. Phase stability, electrochemical stability and ionic conductivity of the Li10±1MP2X12 (M
= Ge, Si, Sn,Al or P, and X = O, S or Se) family of superionic conductors. Energy & Environ. Sci., 2012. doi:10.1039/c2ee23355j
2 N. Kamaya et al.,A lithium superionic conductor. Nat. Mater. 2011, 10, 682-686
activation
energy
(meV)
conductivity
@ 300 K
(mS/cm)
computed1 210 13
experiment2 240 12
Temperature range:
600 K to 1200 K
Computed diffusivities
Aug 12, 2014 ACS 248th National Meeting
9. Ab initio molecular dynamics predict 3D
conduction pathway
Y. Mo, S. P. Ong, G. Ceder, First principles study of the Li10GeP2S12 lithium super ionic conductor material. Chem. Mater. 2012,
24 15-17.
Lithium trace in MD simulation
at 900K
a!
c!
a!
b!
Important because 1D
conductors would be highly
sensitive to blocking defects!
Aug 12, 2014 ACS 248th National Meeting
10. Bandgap is upper bound on electrochemical
window
DOS calculated
with HSE06
3.6 eV
This is how people have estimated
electrochemical windows in the past.
But is it relevant?
Aug 12, 2014 ACS 248th National Meeting
11. A thought experiment
Anode CathodeLGPS
Li sinkLi source
High μLi Low μLi
Aug 12, 2014 ACS 248th National Meeting
12. Now let us imagine what it is like at the
electrode-electrolyte interface
Anode CathodeLGPS
High μLi Low μLi
Li source Li sink
Systems open wrt Li
Aug 12, 2014 ACS 248th National Meeting
13. A new way of assessing electrochemical stability
Relevant thermodynamic potential at electrode-
electrolyte interface is the Li grand potential1:
Construct phase diagrams at extrema of
corresponding to the cathode and anode:
φ = E −µLiNLi
µLi
Voltage = −(µLi −µLi
0
)
1S. P. Ong, L.Wang, B. Kang, & G. Ceder. Li-Fe-P-O2 Phase Diagram from First Principles
Calculations. Chemistry of Materials, 2008, 20(5), 1798–1807. doi:10.1021/cm702327g
Aug 12, 2014 ACS 248th National Meeting
14. Ge
P
GeS
GeS
2
P
4
S
3
P4
S7
S
P2
S5
P
4
S
9
LGPS is unstable against electrodes
Li15
Ge4
Li3
P
Li2
S
Y. Mo, S. P. Ong, G. Ceder, First principles study of the Li10GeP2S12 lithium super ionic conductor
material. Chem. Mater. 2012, 24 15-17
E = 0V E = 5V
Aug 12, 2014 ACS 248th National Meeting
15. LGPS achieves electrochemical stability by
passivation
Li2S + Li15Ge4 + Li3P S + GeS2 + P2S5
Anode CathodeLGPS
High μLi Low μLi
Well-known
glassy conductors!
Aug 12, 2014 ACS 248th National Meeting
16. Summary on Li10GeP2S12
Kamaya et al.
(Experiments)
1D conductor
σ=12 mS/cm
Stable over 5V
First principles
calculations
3D conductor
σ=13 mS/cm
SEI formation
✗
✔
?
Aug 12, 2014 ACS 248th National Meeting
18. Modifying Li10GeP2S12
Two critical problems with LGPS
• Ge is expensive ($1600-1800 per kg)
• S chemistry likely reactive with H2O and air
S Se, OAnion
Ge Si, Sn,Al, PCation
Substitutions
Aug 12, 2014 ACS 248th National Meeting
19. Phase stability of nine Li10MP2X12 derived from
substitution
S. P. Ong,Y. Mo,W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Phase stability, electrochemical stability and ionic conductivity in the
Li10±1MP2X12 family of superionic conductors. Energy Environ. Sci. 2012, doi: 10.1039/C2EE23355J
> 90 meV, oxides
unstable!
< 25 meV, S & Se
compounds may be
entropically
stabilized
Edecomp of
Li10MP2X12
(meV/atom)
Aug 12, 2014 ACS 248th National Meeting
20. Chemical compatibility with electrodes
Possibly passivating ionic conductors
S. P. Ong,Y. Mo,W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Phase stability, electrochemical stability and ionic conductivity in the
Li10±1MP2X12 family of superionic conductors. Energy Environ. Sci. 2012, doi: 10.1039/C2EE23355J
O2
evolution!
Li10MP2X12
Aug 12, 2014 ACS 248th National Meeting
21. Anion has a large effect on diffusivity of
Li10GeP2X12
σ @ 300
K
(mS/Cm)
Ea
(meV)
O 0.03 360
S 13 210
Se 24 190
Causes:
• Lattice parameter
• Anion polarizability
Se
S
O
S. P. Ong,Y. Mo,W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Phase stability, electrochemical stability and ionic conductivity in the
Li10±1MP2X12 family of superionic conductors. Energy Environ. Sci., 2012, doi: 10.1039/C2EE23355J
Aug 12, 2014 ACS 248th National Meeting
22. Cation has a small effect on diffusivity of Li10MP2S12
Isovalent Aliovalent
Ge Si Sn P Al
σ @ 300 K (mS/Cm) 13 23 6 4 33
Ea (meV) 210 200 240 260 180
(Aliovalent substitutions
are Li+ compensated)
S. P. Ong,Y. Mo,W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Phase stability, electrochemical stability and ionic conductivity in the
Li10±1MP2X12 family of superionic conductors. Energy Environ. Sci., 2012, doi: 10.1039/C2EE23355J
Aug 12, 2014 ACS 248th National Meeting
23. Recent experiments validate first principles
predictions!
A. Kuhn et al., 2014, arxiv:1402.4586P. Bron, JACS, 2013, 135, 15694–7.
Aug 12, 2014 ACS 248th National Meeting
24. Voronoi topological analysis of LGPS
Aug 12, 2014 ACS 248th National Meeting
Using Zeo++ code (R. L. Martin,
B. Smit, M. Haranczyk,. Journal of
Chemical Information and
Modeling, 2012, 52(2), 308–18.
Y. Mo, S. P. Ong, G. Ceder,
First principles study of the
Li10GeP2S12 lithium super
ionic conductor material.
Chem. Mater. 2012, 24 15-17.
25. 1.2
1.4
1.6
1.8
2
O O O S S S S S Se Se Se
Si Ge Sn Si Ge Sn Al P Si Ge Sn
~20%
~7%
Bottleneck size as a descriptor for diffusivity
Li±1
Ge4+:Al3+, Si4+, Sn4+, P5+
P5+
S2-: O2-, Se2-
Substitution Scheme 1.0E-3
1.0E-1
1.0E+1
O O O S S S S S Se Se Se
Si Ge Sn Si Ge Sn Al P Si Ge Sn
Conductivity σ
(mS/cm)
Bottleneck size
(Å)
Aug 12, 2014 ACS 248th National Meeting
Generally, bottleneck size seems
to be a pretty good initial
screening descriptor for
diffusivity.
26. State-of-the-art lithium superionic conductors
N. Kamaya et al., Nat. Mater. 2011, 10,
682-686
R. Murugan, et al.,Angew. Chem., Int.
Ed. 2007, 46, 7778−81.
LGPS
One of the highest Li+ cond.
of 12 mS/cm
Reported electrochemical
window of > 5V
Ge is expensive
Sulfide chemistry is air and
moisture sensitive
LLZO
Oxide chemistry is air stable
Stable against Li?
Low grain boundary
resistance
Lower Li+ cond. of ~0.1 mS/
cm
Aug 12, 2014 ACS 248th National Meeting
27. First principles optimization of garnet
Li7+2x−y(La3−xRbx)(Zr2−yTay)O12
0.00
0.10
0.20
0.30
0.40
0.50
6 6.5 7 7.5
Activation
Energy(eV)
1.0E-07
1.0E-05
1.0E-03
1.0E-01
σ300(S/cm)
Rb DopedTa Doped
Max conductivity and min Ea at Li = 6.75
Miara, L. J.; Ong, S. P.; Mo,Y.; Richards,W. D.; Park,Y.; Lee, J.-M.; Lee, H. S.; Ceder, G. Chem. Mater., 2013, 25, 3048–3055.
Aug 12, 2014 ACS 248th National Meeting
28. Voronoi topological analysis of LLZO
Aug 12, 2014 ACS 248th National Meeting
Miara, L. J.; Ong, S. P.; Mo,Y.; Richards,W. D.; Park,Y.; Lee, J.-M.; Lee, H. S.; Ceder, G. Chem. Mater., 2013, 25, 3048–3055.
29. Pathway to High-throughput First Principles
Design of Lithium Superionic Conductors
Aug 12, 2014 ACS 248th National Meeting
Starting candidates
Topological Screening
(augmented by DFT)
Stability (phase
EW) screening
Diffusivity
Optimized
candidates
Automated “one-click” MD
workflow based on pymatgen,
custodian and fireworks
AIMD SDSC
Multi-week AIMD simulation
Statistical exclusionary
screening
Y. Mo, S. P. Ong, G. Ceder,“Insights into Diffusion Mechanisms in P2
Layered Oxide Materials by First-Principles Calculations”, submitted
Automated pathway
extraction + NEB
30. Summary
• Developed sophisticated AIMD automation and workflow
infrastructure for rapid kinetic studies.
• Developed Li-grand potential PD as a powerful new way
of studying electrode-electrolyte interfacial phase
equilibria.
Technical Advances
• Li10SiP2S12 and Li10SnP2S12, earth-abundant variants of
LGPS, were predicted and confirmed to have similar
performance.
• Suggested doping strategies to further enhance
conductivity of LLZO.
Materials Design
Aug 12, 2014 ACS 248th National Meeting
31. Acknowledgements and Publications
Funding
Computing resources from
Y. Mo, S. P. Ong, G. Ceder, First principles study of the Li10GeP2S12 lithium super ionic
conductor material. Chem. Mater. 24 15-17 (2012)
S. P. Ong,Y. Mo,W. D. Richards, L. Miara, H. S. Lee, G. Ceder, Phase stability, electrochemical
stability and ionic conductivity in the Li10±1MP2X12 family of superionic conductors.
Energy Environ. Sci., 2012, doi: 10.1039/C2EE23355J
Miara, L. J.; Ong, S. P.; Mo,Y.; Richards,W. D.; Park,Y.; Lee, J.-M.; Lee, H. S.; Ceder, G. Effect of
Rb and Ta Doping on the Ionic Conductivity and Stability of the Garnet Li7+2 x – y (La3–
xRbx)(Zr2– yTay)O12 (0 ≤ x ≤ 0.375, 0 ≤ y ≤ 1) Superionic Conductor:A First Principles
Investigation, Chem. Mater., 2013, 25, 3048–3055, doi:10.1021/cm401232r.
Aug 12, 2014 ACS 248th National Meeting