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NASA Aeronautics Research Institute
Enabling Electric Aviation with Ultra High Energy Lithium Metal Batteries
NASA Aeronautics Research Mission Directorate (ARMD)
FY12 Seedling Phase I Technical Seminar
July 9-11, 2013
John Lawson-PI (ARC), Tom Miller (GRC), James Wu (GRC), Bill Bennett (GRC), Charles Bauschlicher (ARC), Brianne Scheidegger (GRC), Justin Haskins (ARC)
NASA Aeronautics Research Institute
Electric Aviation
• Green aviation: high efficiency, low emissions, low noise
• Solar Impulse: largest technological limitation -- battery storage
• Hybrid aircraft: battery weight is significant limitation
• Commercial aircraft: battery powered onboard systems
• Boeing 787 Dreamliner: current battery electrolytes are flammable
• Progress in electric aviation will depend on advances in ultra high energy, safe batteries
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 2
NASA Aeronautics Research Institute
• Potential for 5X increase in storage capacity• Safety and cycling problems: issues for Li-Air, Li-S, etc• Holy Grail of advanced battery technology
F. Orsini et al., J. Power Sources 76, 19-29 (1998)
Lithium Metal Anodes
3NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar July 9-11, 2013
Li-Air Battery
Dendrite
LithiumSurface
Battery failure due to dendrites
NASA Aeronautics Research Institute
Two Ionic Liquids are similar but have very different cycling behavior - why?
[EMIM][BF4][pyr14][TFSI]
Ionic Liquid Electrolytes
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 4
Anions
Cations
N. Schweikert et al., J. Power Sources 228, 237-243 (2013)
Good Cycling Poor Cycling
Fundamental understanding will enable design of ultra high energy batteries
NASA Aeronautics Research Institute
Seedling Phase I Project
• Innovation: computational predictive tool tightly coupled to experiments to accelerate fundamental understanding, screening and design of novel electrolytes for advanced batteries
• Application: investigate two Ionic Liquid electrolytes (one good cycling and one poor) for Lithium metal anode batteries
• Cross-Center, Multi-Disciplinary Team
• ARC Computational Materials Group: modern computational material science methods
• GRC Electrochemistry Branch: wide-ranging experience in battery development experimental characterization
• Benefit/Impact: predictive tool for accelerated development of ultra high energy, safe batteries
• Aggressive Work Plan (12 milestones) -- all met or exceeded
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 5
NASA Aeronautics Research Institute
Technical Approach
• Transport simulations
• Experimental validation
• Interface simulations with voltage
• Electric double layer structure
• Electrolyte surface decomposition
• Chemical pathways
• Surface layer formation
I. Isolated Ionic Liquids
III. Ionic Liquid-Electrode interface
IV. Interfacial chemistry
• Build cells
• Electrochemical characterization
• Surface layer identification
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 6
II. Experimental Cell Characterization
NASA Aeronautics Research Institute
I. Isolated Ionic Liquids
II. Experimental Cell Characterization
III. Ionic Liquid-Electrode Interfaces
IV. Interfacial Chemistry
V. Summary/Future Directions
Phase I Seedling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 7
NASA Aeronautics Research Institute
Molecular Dynamics Simulations
• Newton’s law F=ma for atoms
• Bonded interactions:
• Non-bonded interactions:
• “Polarizable” interactions
• New polarizable software module forIonic Liquid simulations developed
• Massive datasets for analysis
EF
[pyr14][TFSI]
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 8
NASA Aeronautics Research Institute
Thermodynamics
Well-established theoretical foundation (statistical mechanics)
CP =¶(H +PV )
¶T P
=d H +PV( )
2
NPT
kBT2
bT =1
V
¶V
¶P T
=dV 2
NPT
V kBT
aP =1
V
¶V
¶T P
=dVd H +PV( )
NPT
V kBT2
gV =¶P
¶T V
=aP
bT
Heat Capacity
Isothermal Compressibility
Thermal Expansion Coefficient
Thermal Pressure Coefficient
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 9
NASA Aeronautics Research Institute
Transport Properties
Non-equilibrium transport coefficients (fluctuation-dissipation theorems)
Dµ dt v(t)v(0)ò
hxy µ dtò pxy (t)pxy (0)
g IC µd
dtqr(t)- qr(0)( )
2
Diffusion
Viscosity
Ionic Conductivity
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 10
NASA Aeronautics Research Institute
Example: Li+ Ion Solvation Shell
Li-TSFI anion
Li-BF4 anion
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 11
Detailed molecular structure
Anion distribution
about Li ions
NASA Aeronautics Research Institute
Density
Excellent agreement with GRC experiments
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 12
Neat Ionic Liquids Lithiated Ionic Liquids
NASA Aeronautics Research Institute
Viscosity
Good agreement with GRC results
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 13
[pyr14][TFSI] [EMIM][BF4]
NASA Aeronautics Research Institute
Diffusion coefficient
Diffusion data from GRC in progress
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 14
[pyr14][TFSI] [EMIM][BF4]
NASA Aeronautics Research Institute
Ionic Conductivity
Good agreement with GRC results
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 15
Conclusion: good agreement on broad range of electrolyte properties
NASA Aeronautics Research Institute
I. Isolated Ionic Liquids
II. Experimental Cell Characterization
III. Ionic Liquid-Electrode Interfaces
IV. Interfacial Chemistry
V. Summary/Future Directions
Phase I Seedling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 16
NASA Aeronautics Research Institute
Lithium Coin Cell
polypropylene gasket
wavespring
spacer
lithium disc (5/8" dia.)
can (positive)
separator (0.8" dia.)
cover (negative)
lithium disc (5/8" dia.)
• Laboratory cells – easily constructed• Focus characterization of the Li metal electrode
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 17
Lithium ElectrodesElectrolyte in porous separator
NASA Aeronautics Research Institute
Cell Cycling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 18
[pyr14][TFSI][EMIM][BF4]
• [EMIM][BF4] cell fails after 150 cycles• [pyr14][TFSI] cell cycles successful up to 1750 cycles
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0 5 10 15 20 25 30
Ce
ll P
ola
riza
tio
n (V
)
Time (min)
Cycle 1
Cycle 100
Cycle 500
Cycle 1000
Cycle 1750
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0 5 10 15 20
Ce
ll P
ola
riza
tio
n (V
)
Time (min)
Cycle 1Cycle 50Cycle 75Cycle 100Cycle 150
Cycles at 60°C Cycles at 20°C
NASA Aeronautics Research Institute
Impedance Spectroscopy
0
1000
2000
3000
4000
5000
6000
0 100 200 300 400 500 600
(Oh
m· c
m2)
Cycle
[pyr14][TSFI]
[EMIM][BF4]
Ch
arg
e T
ran
sfe
r R
es
ista
nc
e
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 19
• [EMIM][BF4] cell has increasing resistance• [pyr14][TFSI] cell has decreasing resistance (increasing Li surface area)
NASA Aeronautics Research Institute
-1 0 1 2 3
Potential (V vs. Li)
2 mA/cm²
[pyr14][TFSI]
[EMIM][BF4] w/ 6% VC
[EMIM][BF4]
Cyclic Voltammetry
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 20
Cu
rren
t Den
sity
• [pyr14][TFSI] cell: Li plating/stripping
• [EMIM][BF4] cell: no Li stripping
• [EMIM][BF4] cell: decomposition
• Consistent with impedance data
• [EMIM][BF4] cell with VC additive improves Li plating/stripping
• Decomposition explored in Phase II
• Additives to be explored in Phase II
NASA Aeronautics Research Institute
Surface Morphology: [pyr14][TFSI]
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 21
• Li electrode after 1780 cycles
• “Mossy” Li deposits rich in electrolyte elements (O, S, F)
• Smooth Li surface visible where mossy layer flaked off
• Mossy layer source of increased surface area
• Consistent with reduction in impedance Exposed Lithium
Mossy Film
Conductive mossy surface layer
facilitates good cycling
NASA Aeronautics Research Institute
Surface Morphology: [EMIM][BF4]
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 22
• Li electrode after 130 cycles
• “Waxy” film covers ~75% of Li surface (rich in F and C)
• Film consists of electrolyte decomposition products
• Li under film appears bright and un-utilized
• Reduction in active area
• Consistent with increase in impedance
Waxy Film
Exposed Lithium
Insulating waxy surface layer results in poor cycling
Fundamental question: Why does one electrolyte give
favorable surface layer and the other does not?
NASA Aeronautics Research Institute
I. Isolated Ionic Liquids
II. Experimental Cell Characterization
III. Ionic Liquid-Electrode Interfaces
IV. Interfacial Chemistry
V. Summary/Future Directions
Phase I Seedling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 23
NASA Aeronautics Research Institute
Electrolyte-Electrode Interface
• Interface simulations with applied voltage (not milestone)• Produced new (second) software module to be distributed• Full interface properties as function of voltage in Phase II
Ionic Liquid Electrolyte Electrode Surface
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 24
Electrode Surface
Question: How does Ionic Liquid organize itself at electrode interface?
NASA Aeronautics Research Institute
Electric Double Layer: [pyr14][TFSI]C
ha
rge
De
nsity (e
/Å3)
0
-0.06
+0.03
TFSI Anion buildup at Cathode
Pyr14 Cationbuildup
at Anode
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 25
V+ V-
NASA Aeronautics Research Institute
Ion Density: [pyr14][TFSI]
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 26
• Molecular layering near interface• Classical theory predicts exponential decay
Conclusion: Molecular ordering near interface sets stage for interfacial reactions
NASA Aeronautics Research Institute
I. Isolated Ionic Liquids
II. Experimental Cell Characterization
III. Ionic Liquid-Electrode Interfaces
IV. Interfacial Chemistry
V. Summary/Future Directions
Phase I Seedling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 27
NASA Aeronautics Research Institute
Surface Reactions: [EMIM][BF4]
Ab Initio Molecular Dynamics• High fidelity modeling• Zero voltage• Ions bound to surface• No decomposition of ions
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 28
BF4
anion
EMIMcation
Question: What are the chemical reactions and products between Li electrode and Ionic Liquid electrolyte?
Lithiumslab
NASA Aeronautics Research Institute
Surface Reactions: [pyr14][TSFI]
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 29
TFSIanion
pyr14cation
Lithiumslab
Ab Initio Molecular Dynamics• High fidelity modeling• Zero voltage• Ions bound to surface• Immediate decomposition of
TSFI anion• Screening tool for electrolytes(?)
Conclusion: At zero voltage, very different anion decomposition behavior and products. Suggests that different surface layers will result (preliminary).
Phase II will consider surface
reactions with applied voltage
NASA Aeronautics Research Institute
I. Isolated Ionic Liquids
II. Ionic Liquid-Electrode Interfaces
III. Interfacial Chemistry
IV. Experimental Cell Characterization
V. Summary/Future Directions
Phase I Seedling
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 30
NASA Aeronautics Research Institute
Summary
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 31
• Phase I Major Accomplishments:– Determined transport properties (computation/experiment) of two ILs
– Built and characterized Li cells (cycling, impedance, voltammetry, SEM/EDAX)
– Identified different surface layers for different electrolytes
– Determined interface double layer properties (computation)
– Identified initial surface reactions from simulations (computation)
• Cross-Center, Multi-Disciplinary Team: ARC/GRC
• Benefit/Impact: predictive tool tightly coupled to experiment for accelerated development of ultra high energy, safe batteries
• Milestones: We have met or exceeded all 12 milestones
• Products: two software modules to be distributed to community
• Dissemination: 3-4 journal articles plus conference presentations
• Interest in Our Work: DOE/ORNL, ARL, IBM Almaden Research
• Spin-off Applications: Ionic Liquids for Tribology, EPSCoR proposal
NASA Aeronautics Research Institute
Future Directions
• Full interfacial properties vs voltage
• Measure interface capacitance
• Surface reactions vs voltage
• Compare to CV data
• Surface layer formation simulations
• Compare to SEM/EDAX data
I. Interfaces under Bias
II. Surface Reactions under Bias
III. SEI growth simulations
IV. Electrolyte Optimization
• Build and characterize full cells
• Optional: Li-Air cell with IL electrolyte
• Optional: Oxidative stability modelingJuly 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 32
V. Full Cells: Cathode and Anode
• Additives and alternative ILs
• Modeling support of optimization
NASA Aeronautics Research Institute
Seedling Team
• GRC Electrochemistry Team • Bill Bennett• James Wu• Tom Miller • Brianne Scheidegger
• ARC Computational Modeling Team • John Lawson• Justin Haskins• Charlie Bauschlicher• Josh Monk• Eric Bucholz
• External Collaborators• Oleg Borodin (ARL)• P. Ganesh (ORNL)• Prof. Farideh Jalilehvand (Univ of Calgary)• Prof. Mohsen Zaeem (Missouri Univ S&T)
July 9-11, 2013 NASA Aeronautics Research Mission Directorate FY12 Seedling Phase I Technical Seminar 33
NASA Aeronautics Research Institute
Thank you for funding!
7/18/201334