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Transcript of Fenómenos interfaciales en las baterías de ion litio y … · Fenómenos interfaciales en las...
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Fenmenos interfaciales en las
bateras de ion litio y de
litio/azufre
Perla B. Balbuena
Department of Chemical Engineering
Department of Materials Science and Engineering
Texas A&M University
College Station, TX 77843
http://engineering.tamu.edu/chemical/people/pbalbuena
Buenos Aires, Agosto 2015
mailto:[email protected]://engineering.tamu.edu/chemical/people/pbalbuena
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Interfacial phenomena
solid
liquidmass transfer
heat transfer
reactions
2
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Lithium-ion battery (rechargeable)
3
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Lithium-ion battery (rechargeable)
https://corneliya.wordpress.com/2013/01/15/interkalationsbatterien-das-problem/ 4
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why batteries?
5
-
.
Necesitamos almacenar la energa
obtenida
Bateras y supercapacitores son las
soluciones mas convenientes
Renewable energies (solar, wind) are intermittent
Energy can be produced
but it must be stored
6
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Where may energy be stored?
Liquid fuels (gasoline, methanol, ethanol)
Gas fuels: Hydrogen (fuel cells)
Hydroelectric dam (potential energy)
Electrochemical cells (batteries:
chemical energy)
7
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what is the current status
of battery technology?
Li-ion dominates the marketportable electronic devices
Expensive, relatively low energy density electric vehicles
8
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Practical vs. theoretical energy density
M. M. Thackeray et al., Energy Environ. Sci., 2012, 5, 78549
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Behavior depends on materials properties
B. J. Landi et al, Energy Environ. Sci., 2009, 2, 638-654 10
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Li-S battery
From Prof. Vilas Pol, Purdue U. https://engineering.purdue.edu/ViPER/index.html11
https://engineering.purdue.edu/ViPER/index.html
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Advantages
S: very abundant
relatively cheap
much less toxic than current Co-oxides
storage capacity: an order of
magnitude > current cathodes
May reach goal of 500 km for EVs and be useful for renewable energies
12
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Li-S battery: cathode
P. G. Bruce et al, Nature Materials, 11, p. 19, (2012) 13
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Li-S battery: anode
P. G. Bruce et al, Nature Materials, 11, p. 19, (2012)
. dendrite formation
. interfacial reactions
. safety issues
. insulating Li2S film on surface
14
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Challenges
Solid S bad ionic/electronic conductor
Changes in S structure during
charge/discharge (swelling, pulverization)
Intermediate compounds shuttle between
electrodes
Li metal anode issues
Low stability short battery life
15
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Interfacial phenomena
solid-liquid interfaces
2
unwanted reactions
16
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Otherwise:
electron
transfer from
electrode to
electrolyte
may occur
eVoc < Eg
Electrochemical stability
LUMO
HOMO
Eg
E
cathode anode
Electrolyte/
separator
mc(Li)
ma(Li)
eVoc
Condition:
Materials design is crucial
17
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First-principles computational
analyses --
understand and predict complex
phenomena
18
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Solid-Electrolyte-Interphase layer
SEI--surface film formed at anode and cathode surfaces
Due to electrolyte
decomposition (reduction
or oxidation)
May protect and stabilize anodes (carbon, Li metal); be unstable (metal-oxide cathodes; silicon anodes)
19
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Thickness: from a
few to tens or
hundreds of
dense inorganic layer
(from salt decomposition)
porous organic layer
(from solvent decomposition)
SEI mosaic composition
Verma, Maire, Novak, EC Acta 2010
20
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How is the SEI layer formed?
21
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EC reductive dissociation
B3PW91/6-311++G(d,p)
In gas phase:
thermodynamically forbidden
Wang, Nakamura, Ue, Balbuena, JACS, 123, 11708-11718, (2001)
In solvent:
1 and 2 e- reductions
are possible
22
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Li+(EC) reductive dissociation
Ion-pair intermediate;
e- is transferred to EC
Much easier !!!
Li salts facilitate the reaction
Homolytic
ring opening
Radical anion
23
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Termination
reactions
lithium butylene dicarbonate
lithium ethylene dicarbonate
+ C2H2
Another e- transfer
Li-carbide
lithium organic salt
with an ester group
insoluble inorganic
Lithium carbonate24
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EC
EC + DEC + LiPF6EC + LiPF6
SEI on carbons for different electrolyte compositions
G. Ramos Sanchez, A. Harutyunyan, P. B. Balbuena, JES, in press
Very different SEI
composition and
product distribution
25
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LithiationMany Cycles
Si
LithiationMany Cycles
SEI
Si
Nano Today, Volume 7, Issue 5, October 2012, Pages 414-429, ISSN 1748-0132
The Si electrode (capacity: one order of
magnitude > carbon)
SEI layer formation
26
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Voltage range
H
O
OH
LiSi
(100)
(101)
Li13Si4
(010)
Highly lithiatedEarly stages of lithiation
LiSi4 LiSi2
~0.2 V0.8 to~0.4 V
LiSi15
27
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Extent of lithiation: Effect on EC reduction mechanisms
Very low lithiationLiSi15
Li over the surface
plane; Si-OE bonds
formed
LiSi2 LiSi4
Li on the surface plane or in the
subsurface: Si-C bonds are formed
Intermediate to high lithiationLi13Si4
1 and 2-e- mech.
can coexist
based on calculated
activation energies
2-e- mech. preferred; at higher lithiation
4 e- mech. observed
CE-O cleavage
Ma and Balbuena
JES, 2014
JM Martinez de la Hoz, K Leung and P B Balbuena, ACS Appl. Mat. and Interfaces, 2013 28
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VC reduction on lithiated Si anodesCleavage of C1O2 bond: VC (ads) + 2e
- OC2H2OCO2-
(ads)
a) Li-O interaction
b) Formation of C-Si bond
c) Ring opening (open VC2-)
d) Cleavage of a 2nd C1O2 bond
CO2 formation results from: VC + CO32- OC2H2OCO2
2- + CO2
CO32- is a product of EC decomposition
(alternative mechanism to Ushirogata et al, JACS 2013)
VC products: open VC2-, OC2H2O2-, OC2H2OCO2
2-, CO, CO2
C=C containing species
J. M. Martinez de la Hoz and P. B. Balbuena, PCCP, 16 (32), 17091-17098 (2014)
Allsurfaces
Higher lithiated
+ 2e-+ 2e-
29
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Effect of degree of lithiation on additives
very low lithiation
FEC: 2 e- mechanism preferred;
CC-OE and Cc-F bond cleavages:
low/moderate barriers
multi-electron
reactions
on highly lithiated
surfaces
2 e- transfer
to FEC ring opening
C-F bond breaking
OC2H3O-, CO2-, F-
OC2H3-, CO2
2-, F-
OCOC2H2O2-, CO2
2-, H, F-open VC2-
FEC can yield open VC anion
(path III) and therefore all VC-
derived products ,
in addition to other specific FEC
products (paths I, II, and III)
J. M. Martinez de la Hoz and P. B. Balbuena, PCCP, 16, 17091-17098 (2014)
Ma and Balbuena
JES, 2014
30
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Effects of electrolyte composition
AIMD simulations of mixtures
of various compositions
Goals: clarify additive and
salt effects in mixtures
Illustration:
mixture 3
15% wt VC
JM Martinez de la Hoz, FA Soto and PB Balbuena, JPCC, 201531
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surface structure and
electrolyte chemistry play big roles;
how does the surface chemistry matter?
-native oxides
-artificial coating
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SiO2 : lithiation and reactivity
hydroxylated amorphous Si surface33
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Lithiation formation energy
-2.25
-1.75
-1.25
-0.75
-0.25
0 0.5 1 1.5 2 2.5 3 3.5 4
Fo
rma
tio
n e
ne
rgy
pe
r S
i [e
V]
x in LixSiO2.48H0.963
E(x) = [E(LixSurface) x E(Limetallic) E(Surface)] / N
Saturation point
34
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Structural evolution
x in LixSiO2.48H0.963
x = 0 0.37 0.74 1.11 1.48
1.85 2.22 2.59 2.96 3.33
S. Perez Beltran, G. E. Ramirez-Caballero, and PB Balbuena, JPCC, 2015 35
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Lithiation mechanisms in native oxides
Si1
Si2O1
Li1
Li2
Li1
Li2
hydroxylated amorphous film LixSiO2.48H0.97
x = 0.37 x = 1.48 x = 3.33
Si-O broken, Si-Si formed, Li6O complexes formed
Perez-Beltran Ramirez-Caballero & Balbuena, JPCC in press 36
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Charge of EC vs.Si-C1 distance
0
1
2
3
4
5
-3
-2.5
-2
-1.5
-1
-0.5
0
0 2000 4000 6000 8000
Si-C
1 d
ista
nce
[]
Ele
ctro
nic
char
ge[e
]
Time [fs]
Totalcharge
O1-Li+ = 2.39
O2-C1 = 1.38
O1-Li+ = 2.02
O2-C1 = 1.75
O1-Li+ = 2.0.6
O2-C1 = 1.65 O1-Li
+ = 2.06 O2-C1 = 3.01
EC(ac) + 2e- O(C2H4)OCO
2-(ads)
Optimized ECmolecule
37
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Aluminum alcoxide (alucon) coating
Collaboration with Chunmei Ban (NREL)
film formation, lithiation, reactivity38
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Film lithiation
-2.63 eV; -3.15 eV; -3.3 eV
binding to
the film stronger
than to Si
agreement with
experiment:
fast film lithiation39
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Electronic conductivity in alucone film
film saturation
once the film is saturated with Li,
it becomes electronically conductive;
SEI reactions observed
Collaboration
with C. Ban (NREL)
Balbuena, Seminario, C.H. Ban et al, ACS Appl. Mater. Inter., 7, 11948, (2015)40
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Role of Additives
at very low lithiation
FEC: 2 e- mechanism preferred;
CC-OE and Cc-F bond cleavages:
low/moderate barriers
multi-electron
reactions
on highly lithiated
surfaces
2 e- transfer
to FEC ring opening
C-F bond breaking
OC2H3O-, CO2-, F-
OC2H3-, CO2
2-, F-
OCOC2H2O2-, CO2
2-, H, F-open VC2-
FEC can yield open VC anion
(path III) and therefore all VC-
derived products ,
in addition to other specific FEC
products (paths I, II, and III)
Martinez and Balbuena, PCCP, 2014
Ma and Balbuena JES, 2014;
K. Leung et al JES 2014
41
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Carbon anodes: effect of surface area
on irreversible capacity
0
500
1000
1500
2000
2500
3000
0 300 600 900 1200 1500
1st
Lit
hi/
de
lith
iati
on
Ca
pa
city
(mA
h/g
)
BET(m2/g)BET (m2/g)
1st
Lith
iati
on
Del
ith
iati
on
Cap
acit
y (m
Ah
/g)
Delithiation
Lithiation
Irreversible capacity
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0 300 600 900 1200 15001
st C
ou
lom
b E
ffic
ien
cy (
%)
BET(m2/g)BET (m2/g)
1st
Co
ulo
mb
Eff
icie
ncy
(%
)
Experimental data from Honda Research Institute, 2014
42
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DFT calculated 1st lithiation
intercalation energy and voltage
c) d)
e) f)a) b)
low surface area
high surface area
Omichi, Ramos Sanchez, Harutyunyan, Balbuena, JES, in press
high surface area carbons: much higher capacity to store Li in the 1st lithiation
43
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Irreversible capacity loss
Omichi, Ramos Sanchez, Harutyunyan, Balbuena, JES, in press44
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Complexation energies of SEI
fragments to LiSpecies Ecomp Ecomp/Li Ecomp-Li
o Ecomp-Li
o /Li
C6O4H10Li5 -9.30 -1.86 -6.59 -3.30
C7O4H15Li3 -6.17 -2.06 -2.78 -2.78
C2O1H5Li2 -4.35 -2.18 -2.25 -2.25
C4O2H10Li5 -9.30 -1.86 -6.59 -3.30
C2O2H4Li7
-5.81 -2.90
C3O2H5Li4 -4.64 -1.16 -1.46 -1.46
C3O3H4Li2
-6.27 -3.13
CO3Li2
-6.38 -3.19
LiF
-4.63 -4.63
45
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Irreversible capacity loss due to SEI
First cycle Second cycle
# C # Li # Li SEI # Li int
G-C 144 104 14 70
Capacity: C6Li4.3 Capacity: C6Li0.83
G-H 144 48 7 0
Capacity: C6Li2 Capacity: C6Li1.7
Table 4. First and second cycle capacity as a function of the functional groups in the edges: G-C is the
highest surface area carbon; G-H is a less-high surface area carbon.
46
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Back to Li-S battery
2 Highly interconnected chemistry47
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Cathode Reactions
S dissolves in electrolyte,
and reacts with Li
EDS Elemental Mapping of
sulfur (29.85 %-wt)
& carbon (65.83 %-wt)
A. Dysart and V. Pol,
Purdue University, 201448
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LiTFSI +
electrolyte
/Li {100}
EC+salt on Li(100)
0 fs 6369 fs
330 K
Anode Reactions
49
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LiTFSI + electrolyte /Li {100}Summary and comparison
EC
EC LiTFSI/EC-sideways LiTFSI/EC-upwards
T [K] Total time [ps] EC-red time [ps] EC-red time [ps] EC-red
330 14 8.0 7 6.4 6 4.3 7
400 14 8.0 7 6.1 6 3.9 6
DOL
DOL LiTFSI/DOL-sideways LiTFSI/DOL-upwards
T [K] Total time [ps] DOL-red time [ps] DOL-red time [ps] DOL-red
330 13 15.0 0 7.0 0 4.7 0
400 13 15.0 0 6.8 0 4.6 1
DME
DME LiTFSI/DME-sideways LiTFSI/DME-upwards
T [K] Total time [ps] DME-red time [ps] DME-red time [ps] DME-red
330 9 15.0 0 6.6 5 5.1 0
400 9 15.0 0 7.6 0 5.0 0
Very reactive
Low reactivity
Intermediate reactivity
Salt decomposes
always; however,
lower reactivity
with DOL
Surface reconstruction generates
sites where dendritic growth
may occur
50
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Shuttle effect: polysulfide
species migrate to anode
51
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Effect of PS species on Li anode
52
Li2S formation
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Conclusions
Very rich interfacial chemistry
Li consumed in SEI layer is irreversibly lost
Need to generate a stable interfacial layer
Li-S chemistry: highly interconnected system
Experimental/theoretical interaction essential
-
AcknowledgementsDOE/EERE DE-EE0006832 and
DE-AC02-05CH11231-Sub 7060634
Honda Research Institute
Special thanks to
supercomputer time from:
Brazos HPC Cluster
Collaborators:
Prof. Jorge Seminario (TAMU)
Prof. Partha Mukherjee (TAMU)
Prof. Vilas Pol (Purdue U)
Dr. Kevin Leung (Sandia Nat. Lab)
Dr. Susan Rempe (Sandia Nat. Lab)
Dr. Chunmei Ban (NREL)
Dr. Avetik Harutyunyan (HRI)
54