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1/27© 3M 2010. All Rights Reserved.
Requirements for practical alloy anode materialsMeltspun alloy material developmentCoating formulation with alloy anodes3M Alloy Materials
3M Alloy Anode Materials27th International Battery Seminar & Exhibit, Ft. Lauderdale FL, March 15-18, 2010
Leif Christensen, Dinh Ba Le, Jagat Singh, M.N. Obrovac3M Electronics Markets Materials Division, 3M Center, St. Paul, MN
2/27© 3M 2010. All Rights Reserved.
501050
501050
20
251025
501050
20
total stack = 240 µm
total stack: 190 µm
20%
ConventionalCathode
GraphiteAnode
ConventionalCathode
Alloy Anode(2X Graphite)
Performance Requirements Practical Alloy Anodes
Increasing cell energy by 20% requires doubling the energy density of graphite electrodesgraphite ≈ 700 mAh/cc
• Battery makers require a significant improvement in performance to adopt a new technology.• Any new alloy material should increase the energy storage by at least 15-20%
Alloy capacity needs to be >1400 mAh/cc** all capacities in this presentation calculated after volume expansion has occurred
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Adjacent Technologies for Alloy Anodes
A number of adjacent technologies are needed to obtain good alloy performance
aqueous binder systemelectrode formulationelectrolyte formulation
above must be compatible with existing cell manufacturing processes
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Material Requirements for Practical Alloys
inexpensive raw materialsinexpensive, high volume manufacturinglow surface area –thermal stabilitynanocrystalline/amorphous structure –cycle life
3M has developed two types of alloy anode materials, use depends on customer application
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Meltspinning Process (Typical High Volume Process for Manufacturing)
meltspinning is a rapid means of making large volumes of nanocrystalline/amorphous metals> 50,000 MT of amorphous alloys are produced yearly by this process
RF Coil
Nozzle
inert gas
metal ribbon
Cu wheel
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Known Meltspun Alloys of Interest for Anodes
Al-M metallic glasses (M = transition metal, rare-earth) [1]
capacity in amorphous range is small (<1000 mAh/cc) [2]
Si-Al-M [3] metallic glassescapacity in amorphous range is suitable (>1400 mAh/cc) [4]
[1] A. Inoue and T. Masumoto, Mat. Sci. and Eng., A133 (1991) 6.[2] M.D. Fleischauer, M.N. Obrovac, J.D. McGraw, R.A. Dunlap, J.M. Topple, and J.R. Dahn, J. Electrochem Soc., 153 (2006) A484-A490.[3] D.V. Louzuine and A. Inoue, Mat. Trans, JIM, 38 (1997) 1095.[4] M.D. Fleischauer, M.N. Obrovac, and J.R. Dahn, J. Electrochem. Soc., 153 (2006) A1201-A1205.
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0 20 40 60 80 100
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0100
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0
AlFe
Si
amorphouspartially crystalline
Si-Al-M Alloys
Six(Al28Fe15)(100-x)/43 compositions prepared by meltspinning
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20 25 30 35 40 45 50 55 60SCATTERING ANGLE (DEGREES)
x = 57
x = 55
x = 48
x = 45
x = 39.4LI
NEA
R IN
TEN
SITY
XRD of Six(Al28Fe15)(100-x)/43 Meltspun Alloys
amorphous materials could be made with x < 57
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Si55Al29.3Fe15.78273C1A
0 200 400 600 800 1000 1200 1400CAPACITY (mAh/g)
0.0
0.2
0.4
0.6
0.8
1.0
VOLT
AG
E (V
)
Six(Al28Fe15)(100-x)/43 Meltspun Alloy Performance
alloys with x = 55, 57 have poor kinetics (first lithiation requires > 48 hours)alloys with x < 55 are inactive
48 hrs
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35 40 45 50 55 60 65x in Six(Al28Fe15)(100-x)/43
0
400
800
1200
1600
1st C
harg
e C
apac
ity (m
Ah/
g)
Six(Al28Fe15)(100-x)/43 Meltspun Alloy Performance
Low Si contents result in poor kinetics or no capacityHigh Si-contents result in crystalline material
Amor
phou
s
Crys
tallin
eAmorphous Si-Al-M alloys with good electrochemical
kinetics are likely not possible by meltspinning.
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Improvement of Meltspun Alloy Performance
alloys with good kinetics require large volume fraction of active materialincreasing the volume fraction of Si in the alloy causes crystallizationadd second active phase
increase total volume fraction of active phasesmain Si active phase stays amorphous
active phase: a-Si
Inactive matrix: Si-Al-Fe
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Improvement of Meltspun Alloy Performance
alloys with good kinetics require large volume fraction of active materialincreasing the volume fraction of Si in the alloy causes crystallizationadd second active phase
increase total volume fraction of active phasesmain Si active phase stays amorphous
2nd active phase
active phase: a-Si
Inactive matrix: Si-Al-Fe
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Requirements for 2nd Active Phase
Require 2nd active phase to form ternary coexistence region
0 20 40 60 80 100
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0100
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0
Si
Al-FeA2
Si-Al-Fe (inactive)
ternary coexistence:Si + A2 + (Si-Al-Fe)
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Requirements for 2nd Active Phase
Require 2nd active phase to form ternary coexistance regionSn forms such a region
0 20 40 60 80 100
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0100
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Si
Al-FeSn
Si-Al-Fe (inactive)
ternary coexistence:Si + Sn + (Si-Al-Fe)
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Results of Adding Sn to Si-Al-Fe Alloys
melting points of Sn and Si-Al-Fe are too dissimilar:Sn = 200°C; Si-Al-Fe alloys ≈ 1000°C
all phases do not solidify simultaneously leading to Sn aggregation during quenchingno change in alloy performance observed with the addition of Sn
20 25 30 35 40 45 50 55 60SCATTERING ANGLE (DEGREES)
0
500
1000
1500
2000
INTE
NSI
TY
0% Sn4% Sn
(Si57Al25Fe15)1-xSnx
16/27© 3M 2010. All Rights Reserved.
Sn-RE as the 2nd Active Phase
Rare-earth (RE) compounds of Sn also form required ternary coexistence regionSn-RE melting point ≈ 1000°C (close to Sn-Al-Fe alloys)
0 20 40 60 80 100
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Si
Al-FeSn-RE
Si-Al-Fe (inactive)
ternary coexistence:Si + A2 + (Si-Al-Fe)
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3M L-19725 Alloy
amorphous Si as major active phaseamorphous inactive phasenanocrystalline Sn-RE minority phase for fast lithium diffusion
nanocrystalline Sn-RE grains well dispersed in alloytotal volume of active phases increased without crystallizing Sngrain boundaries may enhance lithium diffusion
20 25 30 35 40 45 50 55 60SCATTERING ANGLE (DEGREES)
0
100
200
300
400LI
NEA
R IN
TEN
SITY
Sn-RE
Issued and Pending Patents
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3M L-19725 Alloy Electrochemical Performance
addition of Sn-RE phase significantly improves kineticspolarization greatly reduced from Si-Al-Fe alloy
0 200 400 600 800 1000CAPACITY (mAh/g)
0.0
0.2
0.4
0.6
0.8
1.0
VOLT
AG
E (V
)
0 200 400 600 800 1000 1200 1400CAPACITY (mAh/g)
0.0
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1.0
VOLT
AG
E (V
)
3M L-19725Si55Al29Fe16
14157C1A
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3M L-19725 Alloy Electrochemical Performance
capacity = 830 mAh/g, 1580 mAh/ccirreversible capacity = 15%volume expansion = 115%
5 10 15 20 25 30 35 40 45 50CYCLE NUMBER
0
400
800
1200
CA
PAC
ITY
(mA
h/g)
14157C1A
Coin cell test: L-19725 AlloyCoating formulation: Alloy/KB/Li-PAA 93/2/5
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Use of Li-PAA Binder with Alloy
Carboxylic acid groups in CMC form strong bonds with metal surfaces*PAA has many more acid groups on chain than CMC, resulting in significantly better performanceaddition of Li reduces irreversible capacity
0
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CA
PAC
ITY
(mA
h/g)
Li-PAACMCPVDF 300°C/ArPVDF 120°C/vac
10 20 30 40 50 60 70 80 90 100CYCLE NUMBER
*N. S. Hochgatterer, M. R. Schweiger, S. Koller, P. R. Raimann, T. Wöhrle, C. Wurm, and M. Winter, Electrochemical and Solid-State Letters, 11 A76-A80 (2008).
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100 200 300 400 500CYCLE NUMBER
0.970.980.991.001.011.021.03
1.041.051.061.071.081.091.10
CO
ULO
MB
IC E
FFIC
IEN
CY
0
500
1000
1500
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2500C
APA
CIT
Y (m
Ah/
g)
18650 Cell Test: L-19725 Formulated Coating
Capacity retention of L-19725 cell exceeds that of commercial Sn-based cell3M alloy has significantly less RM cost compared to Sn-based alloy
1655w1aL-19725 18650 cellhand made in lab (not optimum)68% retention / 500 cycles
99.96% CE
commercially madeSn-based cell: 61% retention/500 cycles
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L-19725 Si-Based Alloy
4.2 g/cc; 1.0 m2/g; D50 = 7 µm830 mAh/g; 1580 mAh/cc (after volume expansion)volume expansion = 120%
L-19725 is a low surface area large particle alloygood rate capability (similar to graphite)good thermal stability in cells (more stable than graphite in hotbox)
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L-20772 Si-Based Alloy
4.1 g/cc; 4.5 m2/g; D50 = 2.5 µm810 mAh/g; 1570 mAh/cc (after volume expansion)volume expansion = 111%
L-20772 is a smaller particle alloygood thermal stability in cells with electrolyte additive
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Practical Implications of 3M Alloy Materials
Standard laptop battery takes up considerable volume.
Standard Laptop Battery
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Practical Implications of 3M Alloy Materials
Up to 20% of battery volume can be removed by replacing graphite with alloy anode
Equivalent Alloy BatteryStandard Laptop Battery
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Conclusions
3M strategy for alloy anodes:low raw material cost
• competing with graphitepractical manufacturing methods
• Li-ion market needs large volumesconventional slurry/coating techniques
• manufacturers need to drop into existing process
3M has developed two alloy anode materials with the above strategy
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Acknowledgements
This material is based upon work supported by the Department of Energy under Award Number DE-EE0000650
This report was prepared in part as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.