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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


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


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


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


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


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.


0 20 40 60 80 100

100

80

60

40

20

0100

80

60

40

20

0

AlFe

Si

amorphouspartially crystalline

Si-Al-M Alloys

Six(Al28Fe15)(100-x)/43 compositions prepared by meltspinning


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


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


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.


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


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


Requirements for 2nd Active Phase

Require 2nd active phase to form ternary coexistence region

0 20 40 60 80 100

100

80

60

40

20

0100

80

60

40

20

0

Si

Al-FeA2

Si-Al-Fe (inactive)

ternary coexistence:Si + A2 + (Si-Al-Fe)


Requirements for 2nd Active Phase

Require 2nd active phase to form ternary coexistance regionSn forms such a region

0 20 40 60 80 100

100

80

60

40

20

0100

80

60

40

20

0

Si

Al-FeSn

Si-Al-Fe (inactive)

ternary coexistence:Si + Sn + (Si-Al-Fe)


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


0

500

1000

1500

2000

INTE

NSI

TY

0% Sn4% Sn

(Si57Al25Fe15)1-xSnx


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

100

80

60

40

20

0100

80

60

40

20

0

Si

Al-FeSn-RE

Si-Al-Fe (inactive)

ternary coexistence:Si + A2 + (Si-Al-Fe)


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


0

100

200

300

400LI

NEA

R IN

TEN

SITY

Sn-RE

Issued and Pending Patents


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

0.2

0.4

0.6

0.8

1.0

VOLT

AG

E (V

)

3M L-19725Si55Al29Fe16

14157C1A


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


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

200

400

600

800

1000

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).


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

2000

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


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)


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


Practical Implications of 3M Alloy Materials

Standard laptop battery takes up considerable volume.

Standard Laptop Battery


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


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


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.

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