Stabilizing Electrodeposition of Metals in Batteries
Mukul D. Tikekar, Lynden A. Archer
Acknowledgements: DMR1006323, KUS-C1-018-02 & DOE-BESC0001086
CFES Annual Conference, Troy NY February 26, 2015
Why the fuss about Batteries?
Inherent intermittency of renewable
energy generation technologies requires
reliable storage!
Consumer demand for faster, lighter, smaller, more
powerful, portable machines – frustrated by batteries!
http://dvice.com/archives/2009/06/nested-cellphon.php
Why high-energy batteries?
The Lithium Metal Battery
Cathode
Whittingham, M.S., Electrical Energy-Storage and Intercalation Chemistry. Science, 1976.
TiS2; MnO2
Li+ Li+
Li+ Li+
Li+ Li+
Li+ Li+
e-
e-
120-150 mAhg-1
Cathode Layered Materials LiCoO2 / LiFePO4
Anode LiC6
< 370 mAhg-1
Electrolyte Aprotic, Li-ion
Conducting liquid
The Lithium Ion Battery
Murphy, D.W., et al., Materials Research Bulletin, 1978; Lazzari, M. and B. Scrosati, JES, 1980
Max
imu
m E
ne
rgy
De
nsi
ty k
Wh
/kg
Volt
Prius
Tesla MS
USABC 2020
Na, Al, Zn, Cu; Mg!
Opportunities: Rechargeable Metal Anode Batteries (RMBs)
Gasoline
Polymers
Block copolymers
Ionomers
Ceramics
Aprotic solvents
Oligomers
Ionic Liquids
Stopping Dendrites: Proposed Solutions
σ = 10-4 – 10-2 S/cm η < 1 Pa-s
EW: 3 V / 5 V
σ = 10-7 – 10-4 S/cm G’ ≤ MPa EW > 4 V
σ = 10-7 – 10-3 S/cm G’ ~ GPa EW > 4 V
Li3.25Ge0.25P0.75S4 (thio-LiSCON)
Li phosphorus oxynitride (LiPON)
H.-M. Kao, 2004
W. Krawiec, 1995 F. Croce, 1998 C. Capiglia, 1999 F. Croce, 2006 M. Reddy, 2006
H.-M. Kao, 2006
X. Yu, 1997
T. Kobayashi, 2008
A. Patil, 2008
D. E. Fenton, 1973
M. Singh, 2007 G.M. Stone, 2012
Tarascon, 1996
Fan, 1998 Saito, 2007
K. Xu, 2004
A. Bhattacharyya, 2004 J. L. Nugent, 2012
Lithium Dendrite Growth in LMBs
Monroe & Newman, JES 2005
+
Stone, Balsara, et al. JES 2012
An electrolyte modulus similar to lithium metal is required to stop dendrites
T = 90 oC
Cd = Total Charge Passed at Cell Failure
Contradictory Evidence
Electrolyte modulus alone does not determine lifetime of lithium metal battery
Khurana, Schaefer, Archer, Coates JACS, 2014
1M[0.7 LiTFSI + 0.3 LiMX]
Lu, Tu, Archer, Nat. Mater.,2014
Lu, et al. Angew. Chem, 2013
Modeling Dendrite Formation
-
+
Chazalviel, Phys. Rev. A, 1990
I II
Ca
Cc
3
2
0
3
C/C
0
1
0
V/V
0 1
1 0 x/L
Electric field
Li
-
+
cc c c
dCJ dD C
F dz dz
fm= - -
0m
maa a a
dC dD C
dz dz
fm= - +
2
0 0/ ( ) /c c a ae z C z Cf r ee eeÑ = - = - -
V
0 0
Anode Cathode
Structured Electrolyte E
L/V
0
z/L
?
Stability Analysis
• Perturb the cathode profile as
• Expect all other variables to follow a similar variation
• Solve the transport problem for σ
• σ determines the stability of deposition – σ > 0 means unstable deposition – σ < 0 means stable deposition
𝐻 𝑐 = 𝐿 + 𝐻𝑐′𝑒𝜎𝑡𝑒𝑖𝑘𝑥
𝐶 𝑐 = 𝐶𝑐 + 𝐶𝑐′ 𝑧 𝑒𝜎𝑡𝑒𝑖𝑘𝑥
𝜙 = 𝜙 + 𝜙′ 𝑧 𝑒𝜎𝑡𝑒𝑖𝑘𝑥
𝐉 = 𝐉 + 𝐉′ 𝑧 𝑒𝜎𝑡𝑒𝑖𝑘𝑥
c
c m
H
H v
t F
J n
mc L
vH J
F
𝐻 𝑐 = 𝐿 + 𝐻𝑐′𝑒𝜎𝑡𝑒𝑖𝑘𝑥
• The perturbation becomes less stable with increasing wavenumber
• High wavenumber perturbations are stabilized by surface tension
kcrL
σmu/J
unstable
stable
Stabilizing Electrodeposition σ
/J ~
Cd
kL
Tethering just 10% of anions produces a ten-fold reduction in both and kcr; tethering 100% essentially eliminates instability mu
Stop THE Unstable Modes!
kL
All anions mobile
kcrL kL
A fraction (5%) of anions fixed
kcrL
a << λcr a << λcr
A nanoporous electrolyte with a << λcr, high modulus, and liquid-like conductivity may be sufficient to stop growth of unstable modes and dendrite proliferation
σ/J
σ/J
kcrL
σmu/J
unstable
stable
What About Mechanics? σ
/J ~
Cd
kL
( )3
1 1
1
21
s
mm
c
cJZ kZv
kk
Jc k
s zé ùê ú= - -ê ú- ë û
Concentration of current on tips
Migration affected by matrix compression
Tugging of separator on the electrode
σ/J
kL
Caf 0.1
Role of Separator Mechanics
As the electrolyte approaches a single-ion conductor, micron-sized dendrites are suppressed at electrolyte/separator moduli well below GLi ≈ 3.4 GPa.
( )3
1 1
1
21
s
mm
c
cJZ kZv
kk
Jc k
s zé ùê ú= - -ê ú- ë û
tLi
1
2
s
0
1
2
Rbulk
0
Rbulk
s
1
2
I s
I 0
V I 0R1
0
V I sR1
s 0.84
Nanoporous Polymer Electrolytes
dp dp 3nm 7nm
Nanoporous Single-Ion Electrolytes
Nanoporous, almost single-ion conducting electrolytes stabilize electro-deposition of Li-metal in both cycling and polarization studies in symmetric cells.
Cycling Studies Polarization Studies
Y. Lu, M. Tikekar, K. Hendrickson, L.A. Archer, accepted in Adv Energy Mater; Cornell Invention Disclosure 4620 (2015)
Summary & Perspective
• Li batteries based on metallic lithium anodes offer good potential for energy storage at comparable energy densities with fossil fuels
• The most unstable mode for electrodeposition of metals is a strong function of the mobile anion fraction in an electrolyte
• Polymer-inorganic hybrids yield electrolytes with tunable mechanical properties, reasonable ionic conductivity and promising ability to prevent cell failure by dendrite short circuits
• Single-ion conducting polymer electrolytes provide promising solutions towards cost-effective and safe LMBs
• Researchers are now on the cusp of multiple embodiments of Li metal battery technologies capable of partially delivering on the theoretical promise of this chemistry
Z. Tu
Model Nanoporous Membranes
Chu et al., Adv. Mater., 2005
FESEM – Vertically fractured PAA film
Z. Tu
PVDF-Al2O3 Nanoporous Electrolytes
+ PC & 1M LiTFSI
Tu, et al, Adv. Energy Mater., 2013
Tu, et al, Adv. Energy Mater., 2013; Nature Mater., 2014
Z. Tu
T [oC] -150 -100 -50 0 50 100 150
0
200
400
600
800
1000
1200
1400
1600
Sto
rag
e M
od
ulu
s M
Pa
T C
20nm
100nm
200nm
G’ (T=25oC)≈ 0.5GPa
G’ (T=25oC)≈ 0.33GPa
Sto
rage
Mo
du
lus
[MPa
]
μ (T=25oC)≈ 2 mS/cm
μ (T=25oC)≈ 1.25 mS/cm
+ PC & 1M LiTFSI
2.6 2.8 3.0 3.2 3.4 3.6 3.8
1E-4
1E-3
0.01
20nm
100nm
200nm
PEG100nm
DC
io
nic
co
nd
uctivity S
/cm
1000/T K-1
PVDF-Al2O3 Nanoporous Electrolytes
Nanoporous X-linked Polymer Electrolytes
R. Khurana, J.L. Schaefer, L.A. Archer, G.W. Coates, J. Amer. Chem. Society, 2014
< 20 nm
ap() 8
5NA
mb
Ge(,T ) kT
aP ()2b
1MPa
Surface Energy Solutions for LMBs M. Tikekar
Limit Formation of Dendrites
C fa > 0.05 Partially tethered anion
High μc Fast Li-ion conductor
High γ Electrolyte additives (e.g. LiMX)
D << λcr < λmu Nanoporous electrolyte
Contradictory Evidence?
Lu, et al. Angew. Chem, 2013
Electrolyte modulus alone does not appear to determine lifetime of battery
+ +
