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First Principles Calculations and NMR Spectroscopy of Electrode
Materials
Professor Clare Grey University of Cambridge
6/17/2014 Project ID
es055
This presentation does not contain any proprietary, confidential, or otherwise restricted information
2
• Project start date: 1/1/13 • Project end date: 12/31/16 • Percent complete: 33%
• Life (capacity fade) • Performance (high energy density) • Rate
• Total project funding: $1.1M • Funding received in FY13:
$265,913 • Funding for FY14: $272,197
Timeline
Budget
Barriers
• Brett Lucht • Jordi Cabana • Kristin Persson • Guoying Chen • Stan Whittingham
BATT collaborators
Overview
Relevance: Objectives - 2013/14 •Identify major solid electrolyte interphase (SEI) components, and their spatial proximity, and how this changes with cycling (capacity fade) •Complete structural/mechanistic studies of Si (performance) •Investigate local structural changes of high voltage/high capacity electrodes on cycling (performance/capacity fade) 2015/16 •Contrast SEI formation on Si vs. graphite and high voltage cathodes (capacity fade) •Correlate Li+ diffusivity in particles and composite electrodes with rate
3
• Optimizing Si performance – Structures formed on cycling
– Reducing overpotential – Building a better SEI
• SEI studies
– NMR studies of local structure as a function of cycling
• Improving rate performance
(electrode tortuosity studies)
• High voltage spinels
Approach/Strategy
– Development of new platform for in situ studies.
– Li and NMR studies of structure – NMR and electrochemical studies
of Si coatings/surface treatments
– 13C NMR studies of 13C enriched electrolytes to study SEI organic components; 19F and 31P studies of inorganics
– Develop pulse field gradient (PFG) approach to study electrode tortuosity (LiCoO2 current model compound)
– Development of in situ methods to study phase transformations
– In-situ and ex-situ NMR studies of Li+ transport and structural changes
4
Milestones • Identify major components (LiF, phosphates, carbonates and organics) in Si
SEI by NMR methods. (Dec-13). Complete • Correlate presence of SEI components with cycle number and depth of
discharge of Si. Complete preliminary TOF-SIMS measurements to establish viability of approach. (Mar-14) Ongoing. Difficulties encountered with sample reproducibility and Si cracking (TOF-SIMS)
• Identify SEI components in the presence of FEC and VC in Si and determine how they differ from those present in the absence of additives. (Jun-14) Ongoing
• Go/No-Go: Stop Li+ PFG diffusivity measurements of electrodes. Criteria: If experiments do not yield correlation with electrochemical performance. (Sep-14) PFG studies initiated of LiCoO2.
Approach/Strategy (cont.)
Again small clusters only seen in 2nd
process Salager et al. in prep.
Optimizing Si performance: I • Used 29Si NMR and Li NMR to study Si cluster formation and bond breakage as
function of state of charge - Showed that mechanisms for lithiation are different in smaller Si particles
7Li NMR 29Si NMR
200 nm Si 15 nm
• Investigated (Li) defects in Si by DFT-based computations
A.J. Morris et al., Phys Rev B (2012)
Technical Accomplishments and Progress
CF+50nm-Au+SiNWs
CF
SiNWs
Cross sectional SEM images
K. Ogata C. Kerr S. Hoffman
Optimizing Si performance II: Studying nanoparticles by in-situ NMR
Inspired by: C. K. Chan. … R. A. Huggins, Y. Cui, Nature Nanotechnology, 3, 31 (2008)
In-situ NMR of Si Nanowires:
Ideal Model Systems for Studying Mechanisms – allow GITT and PITT
experiments to be followed in situ
P-doped Si
Li15+xSi4 Clusters
Galvanostatic mode
PITT
Detect Si=Si defects in Li15Si4 => Set overpotential voltage on charge
Ogata et al., Nat. Commun. (2014)
SEI Studies: Si
SEI Layer ~ 10 - 100 nm thick
Silicon
1H and 13COrganics
OOOO
O
O
Li
Li
O O
O
Li
LiF19F & 7Li
Li2CO3
7Li & 13C
31P & 19FPF3O
13C
O
OO
13CO
O
O13CH313CH3
Structure of the interface?
System: C + Si, 1 : 1
• SEI as a function of voltage? • SEI as a function of cycle
number?
5
10
15
-300-200-10005
10
15
19F shift / ppm[ppm] 10 5 0 - 5
*
-71.8 ppm LiPF6
-203 ppm LiF
-0.3 ppm
4.6 ppm EC
1.2 ppm CH*3CH2OCO2Li
3.8 ppm LEDC
7Li
1H
Correlate 1H-7Li nuclei in close proximity using 2D experiment
Decomposition product of EC
(-0.43, 3.8)LEDC
7Li
1H
LiO OO OLi
O
O
60 kHz, 700 MHz
-20-10010200100
7Li Shift / ppm
-10-551015 1H Shift / ppm
19F* ****
Decompositionproducts of EC
0
8
40
2
Decomposition product a result of reactions with H2O
1
0 50 100 1500
1
2
3
Volta
ge (V
)
0 50 100 150−200
−100
0
100
Time (hours)
Curre
nt ( μ
A)
0 500 1000 1500 2000 2500
0.5
1
1.5
2
2.5
3
Capacity (mAh/g)
Volta
ge (V
)
C/75
HoldC/75 Irreversible Capacity ~ 920 mAh/gRest
Discharge Capacity ~ 2880 mAh/g
Hold
**
**** **
13C shift / ppm10 kHz MAS
13C shift / ppm10 kHz MAS
250 200 150 100 50 0 250 200 150 100 50 0
13C EC Enriched (RED) 13C DMC Enriched (BLUE)
* *
* *1H - 13C
7Li - 13C
13C
CP ct = 5 ms
CP ct = 500 µs
HEcho
200 100
10
5
0
0 4.5 ppm 1H
4.5 ppm
250 200 150 100 50 0
(EC)67.3 (4.5 1H)
(EC) + (SEI)159 / 161.5
Projection1D cp
13C shift / ppm
13 C
O
OO
ct = 500 µs
Proje
ction
Projection (+)
1D cp
180 160
20
0
- 20
SpinningSidebands(2 Pairs)
3.5 ppm 1H
4.5 ppm 1H
4.5 ppm
3.5 ppm
180 170 160
10
5
0
180 170 160
180 170 160
(EC)159.3 (4.5 1H)(SEI)
LEDC (CH2OCO2Li)2 161.5 (~3.5 1H)
*
13C shift / ppmct = 500 µs
1 H s
hift
/ ppm
(larg
er s
cale
)
13C shift / ppm 13C shift / ppm
1 H s
hift
/ ppm
1 H s
hift
/ ppm
16
1
6
16
****
(SEI)LEDC (CH2OCO2Li)2
161.5 (~3.5 1H)
13C Solid State NMR – SEI Composition
13C Enriched EC DMC
Use correlation NMR experiments (cross-polarization (CP)) to establish spatial proximity between atoms
13C
O
OO
13CO
O
O13CH313CH3
EC: 2D experiments confirm assignments of LEDC (similar experiments performed for DMC)
Collaboration with B. Lucht: Structures of reduced VC and FEC
VC FEC
185 = RCO2 128 = C=C 69 – 71 = OCH2
Very similar polymers .. Now we can compare spectra with those obtained when using VC and FEC as additives
Reducing SEI Formation: Si surface coatings improve capacity retention
APTMS TEOOS
PMVEMA (3-Glycidyloxypropyl)trimethoxysilane
0 5000 10000 15000 20000 25000 30000
0.0
0.5
1.0
1.5
2.0
2.5
3.0 Theoretical capacity: 3750 mAhg-1
Non-coated SNP (cell #1)
APTES-coated SNP (cell #5)
APTES-coated SNP (cell #6)Rate: C/100
Capacity (mAh/g)
Pot
entia
l vs
Li/L
i+ (V
)
5 10 15 20 250
1000
2000
3000
4000
Cycle number
Cap
acity
(mA
h/g)
Comparison: Capacity RetentionDischarge CapacityCharge Capacity
5 10 15 20 25
0.8
1
Cou
lom
b Ef
ficie
ncy
Cycle number
Comparison: Coulombic Efficiency
Discharge CapacityCharge Capacity
APTES-coated
APTES-coated
non-coated
non-coated
- Echem performance improvement: APTMS> Si(CH2)2CN>TEOOS> PMVEMA> >Si(CH2)7CH3 > non-coated
Si(OCH2CH3 )2CH2CH2CN
NMR studies in progress to study nature of grafting
Development of In situ NMR method for Paramagnetic Cathode Materials:
Li1.08Mn1.92O4 Electrode Orientation = 54.7 Degrees
1st cycle
7Li
Relaxation (T2) effects – and thus spectral intensity - are strongly affected by Li motion
0 50 100 150 200 250 3002.83.03.23.43.63.84.04.24.44.6
Capacity(mAh/g)
Volta
ge(V
)
0
20
40
60
80
100
120(118mAh/g)
In-situ T2 (µs)
0 50 100 150 200 2502.83.03.23.43.63.84.04.24.44.6
Capacity(mAh/g)
Volta
ge(V
)
0.00.10.20.30.40.50.60.70.8
Intensity
0 50 100 150 200 2502.83.03.23.43.63.84.04.24.44.6
Capacity(mAh/g)
Volta
ge(V
)
0.00.20.40.60.81.01.21.41.61.82.0 Corrected Intensity via T
2
tau tau - detect
π/2 π
Spin-spin relaxation (T2) measurements:
Use In-situ T2 Measurements to Study Li Dynamics as a Function of Temperature
• Rapid Li+ and electronic motion in partially charged samples • Clear evidence for solid solution from 1 Li to 0.5 Li • Ordering tendency @ 0.5 Li -
• Method can be used to study dynamics during (de)lithiation
0.0 0.5 1.0 1.5 2.0 2.5 3.0
20406080
100120140
700750
in s
itu T
2 (µs
) RT 40T 60T 70T
(ppm
)
°C
°C °C
Solid solution
2 phase
Cation ordering
21 mV
High Voltage Spinels (Li(Ni0.5Mn1.5O4) - Ordering affects the electrochemistry @ the 4.8 V process
9 Mn4+ 3 Ni2+
8 Mn4+ 4 Ni2+ 10 Mn4+ 2 Ni2+
6 Li NMR
946 ppm
P4332: Ni2+ and Mn4+ ordering
Fd-3m: Ni2+ and Mn4+ randomly distributed
DISORDERED
ORDERED
50 mV
50 mV
With J Cabana (LBNL/UIC) C Kim (LBNL)
In-situ 7Li NMR – Mechanisms of (de)lithiation
Disordered 900 C spinel
Increased Li mobility Solid solution
Intensity T2 corrected
2 - phase “T2” Relaxation studies show solid solution followed by 2 phase
Cation ordering @ x = 0.5
Intensity vs. cycling
In-situ 7Li NMR – Lithium & electrolyte region: Follow Li
dendrite formation and electrolyte decomposition in
situ
Electrolyte decomposition
Dendrite formation
Ordered
18
Summary • Silicon – structural work essentially complete. • Used 29Si NMR to study cluster formation on lithiation • Developed in-situ NMR method for studying nanowires • Identified source over large “overpotential” on charging fully lithiated
Li15Si4 phase • Si SEI – NMR methodology has been developed. • Clear NMR signatures of many SEI components identified • Si Coatings – Grafting of small molecules helps improve
capacity retention. • Tortuosity – PFG method demonstrated • High Voltage spinels – Demonstrated novel NMR methodology
to study paramagnetic materials • Approach can be used to study Li ion dynamics, cation ordering,
solid solution vs. 2-phase behaviour • Used to study nature of electrode reactions for the high voltage
spinel Li(Ni0.5Mn1.5)O4, electrolyte decomposition and Li dendrite formation
• Ex-situ NMR highly sensitive to cation (Ni/Mn) order
Future Work •Silicon structure Future work will focus on (i) Reverse Monte Carlo simulations of amorphous phases (with pair distribution function analysis) to quantify Si amorphous structures and (ii) the effect of P doping on rate, overpotential (energy efficiency) and lithiation mechanisms. •Si SEI •Further 2D NMR experiments of fully enriched EC will be performed for more detailed structure solution of decomposition products (including reduced FEC/VC) •Future work will focus on cycling studies, and structure f(voltage) and VC/FEC •C-Si experiments will be initiated to investigate SEI/Si interface •Si Coatings •Detailed NMR studies will be performed to understand nature of grafting and how that changes with cycling. Use results/understanding to investigate different molecules
•Tortuosity •PFG method will be applied to cycled/discharged samples to explore how SEI growth affects tortuosity (and rate) •Investigation of Si/conducting polymer samples prepared by Gao Liu (LBNL) – particularly to investigate conductivity in pores and binder – are planned •High Voltage spinels •Separate equilibrium from non-equilibrium processes in NMR •Initiate work on SEI of HV spinels. Combine with graphite carbon for full cell studies. •Extend method to other high voltage systems.
20
Collaboration and Coordination with Other Institutions
• Dupont CR&D (E. McCord and W. Holstein) – Investigation of electrolyte stability and SEI formation
• Brett Lucht (Rhode Island) – Investigation of SEI
• Jordi Cabana (UI Chicago) – synthesis, XRD of high voltage spinels
• Stanley Whittingham (Binghamton) – magnetism of spinels
• Stephan Hoffman (Cambridge) – Si nanostructures
• Andrew Morris (Cambridge) – DFT structures of LixSi
• Guoying Chen (LBNL) – synthesis of high voltage spinesl
• N/A – not reviewed last year
Responses to Previous Year Reviewers’ Comments
21
Technical Back-Up Slides
22
Publications and Presentations • “Structure of aluminum fluoride coated Li[Li1/9Ni1/3Mn5/9]O2 cathodes for secondary lithium-ion batteries”, K.J.
Rosina, M. Jiang, D. Zeng, E. Salager, A.S. Best, C.P. Grey, J. Mat. Chem., 22, 20602-20610, (2012). • “Scanning x-ray fluorescence imaging study of lithium insertion into copper based oxysulfides for Li-ion batteries”,
R. Robert, D. Zeng, A. Lanzirotti, P. Adamson, S.J. Clarke, and C.P. Grey, Chem. Mat., 24, 2684-2691, (2012). • “Sidorenkite (Na3MnPO4CO3): A new intercalation cathode material for Na-ion batteries”, H. Chen, Q. Hao, O.
Zivkovic, G. Hautier, L.-S. Du, Y. T, Y.-Y. Hu, X. Ma, C.P. Grey, and G. Ceder, Chem. Mat., 25, 2777-2786 (2013). • “Study of the transition metal ordering in layered NaxNix/2Mn1–x/2O2 (2/3 ≤ x ≤ 1) and consequences of Na/Li
Exchange”, J. Cabana, N.A. Chernova, J. Xiao, M. Roppolo, K.A. Aldi, M. Stanley Whittingham, and C. P. Grey, Inorg. Chem., 52, 8540-8550 (2013).
• “Paramagnetic electrodes and bulk magnetic susceptibility effects in the in situ NMR studies of batteries: Application to Li1.08Mn1.92O4 spinels”, L. Zhou, M. Leskes, A.J. Ilott, N.M. Trease, and C.P. Grey, J. Mag. Res., 234, 44-57 (2013).
• “Lithiation of silicon via lithium Zintl-defect complexes from first principles”, A.J. Morris, R.J. Needs, E. Salager, C.P. Grey, C.J. Pickard, Phys. Rev. B, 87, 174108-1 – 174108-4, (2013).
• “Revealing the kinetics of key LixSi phase transformations in nano-structured Si based Li-ion batteries via in situ NMR”, K. Ogata, E. Salager, C. J. Kerr, A. J. Morris, A. Fraser, C. Ducati, S. Hofmann, C. P. Grey, Nature Communications, 5:3217 | DOI: 10.1038/ncomms4217 (2014). “Following Function in Real Time: New NMR and MRI Methods for Studying Structure and Dynamics in Batteries and
Supercapacitors” Talk (or related talk) given at the following meetings in 2013: iNano Opening, Plenary Talk, Billund, January; Chemistry Department, ENS Lyon, January RS, Theo Murphy International Scientific Meeting, 28 & 29 January; Chemistry Department, University of Wisconsin, February; IBA2013, Research Award Address, Barcelona, March; ACS, New Orleans, March 54th ENC, Laukien Award Address, Asilomar, CA, April; ISMAR 2013, Rio de Janeiro, Brazil, May University of Basel, Basel, May; SSI-19 Conference, Kyoto, June RSC MC11, Warwick University, July; ICMRM, Cambridge, August Electrochem2013, Southampton University, Southampton, September; RSC ISACS12, Cambridge, September 8th Alpine Meeting on Solid State NMR, Chamonix, September; LG Chemicals, Daejeon, Korea, October Korea Basic Science Institute, Daegu, Korea, October; Department of Energy Science, Sungkyunkwan University, Korea, October Samsung Advanced Institute of Technology (SAIT), Seoul, Korea, October Institute of Energy & Climate Research, Forschungszentrum Juelich, Germany, November MRS, December (2013).
• Susceptibility effects and dipolar broadening are significant for paramagnetic samples
2000 1500 1000 500 0 -500 -1000 -1500
ppm
Rotation angle α =90o(Horizontal) Rotation Angle α =54.7o(Magic Angle) Rotation Angle α =0o(Vertical)
-159
527
837 LiMn2O4 vertical
horizontal
Challenges for In-situ NMR: Paramagnetic Cathode Materials
Li
Mn θ LiMn2O4
B0
L. Zhou, et al. JMR 2013
-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
-200
0
200
400
600
800
1000
Spi
nel P
eak
Pos
ition
(ppm
)
Rotation Angles(Radians)
x-rotation y-rotation z-rotation
δiso= 520 ppm
Li1.1Mn1.9O4 electrode: rotation plot
54.7° - the magic angle..
Orientation of battery film at the magic angle minimizes susceptibility effects
In-situ 7Li NMR – Ordered vs Disordered
Ordered Disordered
Increased Li mobility Solid solution Limited range of
Solid solution
Intensity T2 corrected
Intensity T2 corrected
hysteresis reversible
More 2-phase like
(331)
OO700
(331)
Charge
Discharge
A900
Chunjoong Kim, Jordi Cabana In-situ XRD: Ordered vs. Disordered
y
z
x
• Samples are saturated with electrolyte solvent (DMC) and diffusion is measured along the z-axis and length of sample
Silicon Composite Electrode
Substrate
Surface of pristine electrode prior to saturation with DMC
Quantify tortuosity using Do=τDeff
PFG NMR Experiments Si and LiCoO2
FinalInitial
<(x’-x)2> = 2Dt
δ/2
∆ Diffusion Time
gi
δ1 δ2
RF
g(t)
S(g) = S(0)exp[-D(γδgi)2(∆-δ/3)]
= S(0)exp[-bD]Encode Decode
0.1
1
Inte
grat
ed S
igna
l Int
ensi
ty (a
.u.) DMC Saturated Sample (b)
Deff = 1.6x10-9 m2/s (*)
Free DMC (**) Do = 2.0x10-9 m2/s
Normalized Gradient Strength
(��G)2����/3) (108 s/m2) 0 5 10 15 20• Unrestricted diffusion distance (2DΔ)1/2 >>
average pore size in diffusion time Δ = 20 ms
• Apparent tortuosity given by τ = Do/Deff = 1.3 (room temperature)