development of materials for high energy batteries

Physical Sciences Inc. 20 New England Business Center Andover, MA 01810

Physical

Sciences Inc. VG11-193

Development of Materials for

High Energy Batteries

Christopher M. Lang (PI), Anna Cheimets and John D. Lennhoff

NASA Battery Workshop 2011

Huntsville, AL

November 15, 2011

SBIR Data Rights

Contract No.: NNX10CA51C

Contractor Name: Physical Sciences Inc.

Contractor Address: 20 New England Business Center, Andover, MA 01810

Expiration of SBIR Data Rights Period: 27 December 2015

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restricted during the period shown as provided in paragraph (b)(4) of the Rights in Noncommercial Technical Data and Computer Software Small Business

Innovative Research (SBIR) Program clause contained in the above identified contract. No restrictions apply after the expiration date shown above. Any

reproduction of technical data, computer software, or portions thereof marked with this legend must also reproduce the markings.

Physical Sciences Inc. VG11-193

Outline

Metal Phosphate Coating for Improved

Cathode Material Safety

Funded by NASA Johnson Space Center and NASA

Glenn Research Center under contract #

NNC09CA04C. COTR: Dr. Judith Jeevarajan.

– Motivation and Coating Benefits

– Program Results

Electrochemical Performance of Silicon Whisker

and Carbon Nanofiber Composite Anode

Funded by NASA Glenn Research Center under

contracts NNX09CD30P and NNX10CA51C. COTR:

Dr. Richard Baldwin.

Summary and Next Steps

-1


Focus\Accomplishments for Year 2 of the Program

Application and scale-up of the coating developed in year 1 to NASA’s specified

mixed metal oxide cathode material (TODA MNC-9100) in order to support

evaluation in cells constructed by NASA’s commercialization partner.

Demonstration of the cycling and safety performance characteristics of the PSI

coated cathode material.

Optimized coating procedures for coating TODA cathode material.

Coating reduces exotherms observed on heating delithiated cathode material.

Coated cathodes demonstrated <1% loss in discharge capacity over 50 cycles at

a C/5 rate.

Demonstrated scale-up with construction of 1Ah pouch cells: – No reduction in discharge capacity or voltage observed.

– On abuse testing pouch cells utilizing coated cathode material demonstrated

improved stability.

Successfully scaled-up cathode coating to produce and deliver 1500grams of

coated cathode material.

-2


Problem:

Under abuse conditions, exothermic reactions between high voltage

cathode materials and the battery electrolyte can lead to catastrophic

failure.

Remediation Approach:

PSI formed lithium metal phosphate coatings on metal oxide cathodes

by thermal treatment of a mixture of metal phosphate and the cathode.1

Motivation

1PSI patenting pending process.

Cathode

LiMPO4

ThermalTreatment

Mx(PO4)y

J-8384

Cathode

-3


Coating is a lithium conductor.

Metal phosphates offer greater stability than their metal oxide

counterparts.

Coating technique can be applied to protect any high energy density

cathode material.

Common processing steps allowing for low cost manufacturing.

Benefits of the Lithium Metal Phosphate Coating

-4


Key Benefit: Cathode Surface Oxidation State

For high voltage cathode materials:

VMox (Oxidized Metal Potential) > VEl-limit (Stability limit of the Electrolyte)

Results in spontaneous oxidation of the electrolyte.

For coated material, the lithium metal phosphate layer remains in the

reduced form upon full charge.

Lithiated

Metal Oxide

Cathode

LiMxPO4

Discharge Charged

Delithiated

Metal Oxide

Cathode

-5


DSC Testing Technique

DSC (differential scanning calorimetry) tests were performed to demonstrate the effect of the coating on the thermal stability of the cathode material in its delithiated state.

Testing Technique:

Half-cells (with a lithium counter) were built using PSI’s puck cell fixture and charged to 4.8V at 12.5mA/g (a C/20 rate).

Cathodes were harvested and rinsed with DMC. DSC tests were performed after drying.

Small punches were taken from the cathode and sealed in the DSC pans.

All DSC pans were pre-run from 25-350°C at 5°C/min to provide a baseline.

Spring Loaded Puck Cell DSC Sample Pans

-6


Heat Flow vs. Temperature for Dry, Delithiated Uncoated and

Phosphate Coated TODA Cathode Material

Coatings adjusted to minimize phosphate content.

All exotherms are muted with exotherms for optimized sample of -1W/g or less.

Peak heights for initial coated sample exotherms are less than -2W/g.

Ramp at 5°C/min

Uncoated

Optimized Coating (Grey)

Coating A(Blue)

-7


C/20 Steady State Cycling Voltage Profile: Cycle 2

Discharge capacity of coated cells is 211 and 206mAh

Discharge capacity of uncoated cells is 208 and 204mAh

No observed difference in voltage trace

-8

2.8

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

0 50 100 150 200

Vo

ltag

e (

V v

s L

i+/L

i)

Capacity (mAh/g-cathode)

Coated

Coated

Uncoated

Uncoated

Cycle Testing: C/20Coated and Uncoated Full Cells vs.

CarbonVoltage Limits 4.6V and 2.8V

Celgard 2500 Separator1M LiPF6 in DEC/DMC/EC


Variable C-rate Cycling of Coated TODA

Variation in capacities results from slight variation in anode to cathode ratios

Cells cycled on initial 26 cycle procedure and then for an additional 50 cycles at C/5

For each cell, capacity on cycle 76 is equal or higher than capacity on cycle 6

150

160

170

180

190

200

210

0 10 20 30 40 50 60 70 80

Cycle #

Dis

ch

arg

e c

ap

acit

y (

mA

h/g

-cath

od

e)

S-3

S-2

S-1

Cycle Testing

Coated Full Cells vs. Carbon

Voltage Limits 4.6V and 2.8V

Celgard 2500 Separator

1M LiPF6 in DEC/DMC/EC

Testing Restarted

C/20

C/10

C/5

-9


First Cycles for

Coated and Uncoated Pouch Cells

Pouch cells were conditioned at C/20 between 4.6 and 2.8V

First cycle efficiency is ~69% for each cell

Initial discharge capacity is consistent with coin cell experiments

2.8

3.2

3.6

4.0

4.4

4.8

0 200 400 600 800 1000 1200 1400 1600

Capacity (mAh)

Cell

Vo

lta

ge

(V

)

Pouch Cell First C/20 Cycle




Coated: Black and Grey

Uncoated: Blue and Red

-10


Third Cycle for

Coated and Uncoated Pouch Cells

Final C/20 cycles before overcharge.

No polarization observed for coated or uncoated cells.

Cell capacity is similar for coated and uncoated pouches.

2.8

3.2

3.6

4.0

4.4

4.8

0 200 400 600 800 1000 1200

Capacity (mAh)

Cell

Vo

ltag

e (

V)

Pouch Cell Third C/20 Cycle




Coated: Black and Grey

Uncoated: Blue and Red

-11


Uncoated Cell Discharge Capacity after Abuse Testing

All tests performed by charging to 4.5V at C/10.

After overcharge testing to 5.5V, the cell capacity was 0.9Ah vs. 1Ah after 4.8V charge.

After short-circuit test, the cell capacity was 0.88Ah.

No observable cell damage noted due to testing.

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

0 2 4 6 8 10 12 14

Time (hours)

Cell

Vo

lta

ge

(V

)

Initial Discharge

Discharge After Overcharge Testing

Discharge After Discharge to 1V

Discharge of Uncoated Pouch Cell after

Abuse Testing and Charge to 4.5V

Current 70mA; Voltage Limit 2.8V



-12


Coated Cell Discharge Capacity after Abuse Testing

All tests performed by charging to 4.5V at C/10.

After overcharge testing to 5.5V, the cell capacity was 1Ah vs. 1.05Ah after 4.8V charge.

After short-circuit test, the cell capacity was 1.01Ah.

No observable cell damage noted due to testing.

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

0 2 4 6 8 10 12 14

Time (hours)

Cell

Vo

lta

ge

(V

)

Initial Discharge

Discharge After Overcharge Testing

Discharge After Discharge to 1V

Discharge of Coated Pouch Cell after

Abuse Testing and Charge to 4.5V

Current 82mA; Voltage Limit 2.8V



-13


Impedance Testing Before and After Abuse Testing

Initially the ionic conductivity of the two cells is nearly equivalent with slightly higher

electrical resistance for the coated cell.

After overcharge and short-circuit testing ionic conductivities remain similar though

electrical resistance for the uncoated cell increases more than for the coated cell.

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.0 0.5 1.0 1.5 2.0

Z' (W)

Z" (W

)

Coated Cell After Conditioning

Uncoated Cell After Conditioning

Coated Cell After Abuse

Uncoated Cell After Abuse

Impedance of Pouch Cells

Test at OCV

Resistance to Ion Flow

Electrical Resistance

-14


Impedance Testing after Storage at 90°C

Uncharged pouches placed in oven at 90°C for 5.5 hours.

Neither cell catastrophically failed, but the uncoated cell appeared to lose some vacuum.

Coated cell demonstrated increase in electrical resistance, but not ionic resistance.

Both the electrical and ionic resistance for the uncoated cell increased by >3X.

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0 2 4 6 8 10 12 14 16

Z' (W)

Z" (W

)

Coated Cell After Abuse

Uncoated Cell After Abuse

Coated Cell After 90C Test

Uncoated Cell After 90C Test

Impedance of Pouch Cells

Test at OCV

Resistance to Ion Flow

Electrical Resistance

-15


Summary of Cathode Coating Results

Optimized coating procedures for coating TODA cathode material.

Coating reduces exotherms observed on heating delithiated cathode

material from greater than -5W/g to less than -1W/g.

Coated cathodes demonstrated <1% loss in discharge capacity over

50 cycles at a C/5 rate.

Demonstrated scale-up with construction of 1Ah pouch cells:

– No reduction in discharge capacity or voltage observed.

– On abuse testing pouch cells utilizing coated cathode material demonstrated

improved stability with reduced impedance growth on abuse testing.

Successfully scaled-up cathode coating to produce and deliver

1500grams of coated cathode material.

-16


Outline



Electrochemical Performance of Silicon

Whisker and Carbon Nanofiber Composite

Anode

– Background, overview and previous results

– Scale-up efforts

– Full cell performance


-17

SBIR Rights in Data


Current Silicon Anodes

Illustration of destructive stress

incurred by volume change

during electrochemical cycling.

Silicon anodes reported in the literature*: 1. Pure Si micro- and nano-scale powder anodes,

2. Si dispersed in an inactive matrix,

3. Si dispersed in an active matrix,

4. Si anodes with different binders,

5. Si thin films.

* U. Kasavajjula, C. Wang and A. J. Appleby, Journal of Power Sources, 163, 1003–1039, (2007).

** C. K. Chan, H. Peng, G. Liu, K. McIlwrath, X.F. Zhang, R. A. Huggins and Y. Cui, Nature Nanotechnology, 3, 31 – 35. (2008).

Silicon nanowire based anode by Chan et al. **:

Silicon nanowire on Stainless steel After cycling

- Demonstrated high capacity and rate capability

-18

SBIR Rights in Data


PSI Concept: Formation of a

Silicon Whisker and Carbon Nanofiber Composite

Silicon Whiskers/Nanowires on Carbon Nanofiber

Silicon Whiskers

100 nm

J-8382

Nanocarbon Fiber

Material Advantages: High in free volume;

Free of polycrystalline domains (not achievable for silicon anode by CVD);

Tailorable silicon loadings;

Supporting matrix forms an electronically conductive framework;

Processable using established procedure and equipment.

-19

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Cycle Life Performance of the

Silicon Whisker/Carbon Fiber Composite

Discharge: anode lithiation; Charge: anode de-lithiation

All capacity values were calculated based on composite weight

Silicon-on-fiber

architecture

demonstrated with

growth proportional

to reaction time.

Good cycle life

achieved for > 200

cycles;

C/10 cycles seems to

be necessary to

stabilize the cell;

Single crystalline

silicon whiskers are

capable of cycling at

high rate of 1C

0

500

1000

1500

2000

0 50 100 150 200

Cycles

An

od

e C

om

po

sit

e C

ap

acit

y (

mA

h/g

)

Delithiation capacity

Lithiation capacity

Composite Anode Cycled vs. Li

Three cycles at C/10 then 1C

100% DOD

-20

SBIR Rights in Data


Successful Material Production Scale-up

Following initial property demonstration, research efforts focused

on moving from producing ~0.5g to 50grams of material per batch.

– Progressively larger batches were run demonstrating linearity and

scalability of the composite formation process.

– Agitation of the sample provides for uniform deposition\material formation.

– PSI has larger reactors that will be utilized for further material production

scale-up efforts.

Electrode optimization has focused on improving the electrode

uniformity to allow for continuous anode material production.

– PSI is producing sufficient electrode for Ah-sized cells and in follow-on

efforts will work to demonstrate electrode production at a pilot casting

facility.

-21

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Rate Performance of Initial High Loading Electrodes

Research has been focused on increasing the material loading from

~0.5mAh/cm2 to ~3-4mAh/cm2.

At low rates, capacities >1000mAh/g-composite were still achievable.

Upon increased rate testing significant polarization was observed

resulting in reduced performance.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.2 0.4 0.6 0.8 1.0

Silicon composite capacity (mAh/g)

Vo

lta

ge

(V

)

100 mA/g

500 mA/g

Anode half cell vs. Li metal

Single layer anodes

Si-composite mass: 4.1 mg/cm2

Separator: Celgard 2500

Electrolyte: 1M LiPF6 in DEC/DMC/EC

(1/1:1:1)

-22

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Improved Performance on Process Optimization

Testing of electrodes in half-cells at C/10 and C/2 was performed to determine the

impact of different processing procedures on performance.

Processing of the composite and slurry was adjusted to improve the cast

uniformity and performance resulting in reduced performance fade on half-cell

cycling at C/2 rates.

0

200

400

600

800

1000

1200

0 2 4 6 8 10

Cycle number

Cap

acit

y (

mA

h/g

)

Gen. 1 Electrode

Gen. 2 Electrode

Anode half cell vs. Li metal

Single layer anodes

Si-composite mass: 3.8-3.9 mg/cm2


Electrolyte: 1M LiPF6 in DEC/DMC/EC (1:1:1)

100mA/g500mA/g

-23

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Successful Transition from Coin to Pouch Cell

Pouch cells of ~75 and ~150mAh have been constructed to demonstrate the

bulk properties of the electrodes and materials.

Initial cycle at 50mA/g-composite was performed to compare coin and pouch cell

performance.

First cycle reversibility is 80-85% using this type of initial cycling procedure.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 250 500 750 1000 1250

Specific capacity (mAh/g)

Ce

ll V

olt

ag

e (

V v

s.

Li+

/Li)

Discharge of Coin cellCharge of Coin cellCharge of Pouch cellDischarge of Pouch cell

50mA/g Initial Cycling of Coin and Pouch Cells

Silicon Composite~3.1mg/cm2


Electrolyte: 1M LiPF6 in DEC/DMC/EC (1:1:1)

with Additives

Charge Extended to Address

Initial Irreversibility

Discharge Capacity Improved

-24

SBIR Rights in Data


Full Cell Performance Demonstration

Coin and pouch cells were tested at various rates with similar performance

measured for each type of cell.

Utilizing the silicon anode 2.5Ah pouch cells have been designed and are being

built. These cells will offer a 7% increase in the cell energy density as compared

to using graphite anode material. The silicon anode reduces the anode material

weight from 15-20% of the total cell mass to 6-8% of the total cell mass.

-25

0

200

400

600

800

1000

1200

0 5 10 15 20

Sp

ec

ific

Ca

pa

cit

y (

mA

h/g

)

Cycle Number

Pouch Discharge

Coin Discharge

50 mA/g50 mA/g

100 mA/g100 mA/g

200 mA/g200 mA/g

500 mA/g500 mA/g

100 mA/g1000 mA/g

200 mA/g100 mA/g

Full cells cycling versus NCA cathodesElectrolyte: 1 M LiPF6 in 1:1:1 (DC:EC:DMC) + AdditivesSeparator: CelgardCycling rate: Printed above, pouch cell rate in red.Voltage limits: 4.05 volts on charge, 2.5 volts on discharge

SBIR Rights in Data


Silicon Anode Program Summary

PSI has developed a silicon whisker and carbon nanofiber composite

material capable of reversibly delivering >1000mAh/g at up to 1C rates.

Composite fiber production has been successfully scaled to 50 gram

scale, with a clear path to production of 250-500 gram batches.

Electrode formulation optimized to produce electrodes delivering

1000mAh/g at the desired loadings.

Equivalent pouch (150+mAh) and coin cell performance demonstrated.

– Production of 2.5Ah pouch cells to be completed as part of research effort.

-26

SBIR Rights in Data


Outline



Electrochemical Performance of Silicon

Whisker and Carbon Nanofiber Composite

Anode


-27


Summary of NASA Sponsored

Battery Material Development Efforts

PSI has successfully developed a cathode coating process that improves the cycling and safety performance of high energy density cathode materials.

PSI has developed a silicon whisker and carbon nanofiber composite material capable of reversibly delivering >1000mAh/g at up to 1C rates.

PSI has successfully demonstrated scale-up of the anode and cathode technologies and has developed a clear path to further scale-up.

Equivalent performance in the coin and pouch cell formats demonstrates PSI ability to successfully scale-up and transition these novel technologies to a sufficient scale for application based testing.

Future funded research effort will construct cylindrical cells utilizing composite silicon anode and high energy density cathode materials.

-28


Acknowledgements

Anode Program:

– Special thanks to NASA for supporting this program under contracts NNX09CD30P

and NNX10CA51C.

– Dr. Richard Baldwin, William Bennett and the NASA Glenn Battery Group

Electrochemistry Branch

NASA Glenn Research Center, Cleveland, Ohio

Cathode Program:

– The cathode work was supported by NASA Johnson Space Center, Houston, TX

77058 and NASA Glenn Research Center, Cleveland, OH 44135 under a NASA NRA

(contract # NNC09CA04C).

– Special thanks to:

– Dr. Judith Jeevarajan (COTR), Thomas B. Miller, Jon S. Read, and Pranav Patel for

their assistance during the program.

All past and present PSI staff who have helped in the execution of these

programs including:

• Kara Constantine, Junqing Ma, Ngoc Do, Alex Elliott, Michael McAllister, Peter

Moran, Aron Newman, Nihala Thanikkal, Jose Vega

-29

Thank you for your time.

Any Questions?

VG11-193


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-31

development of materials for high energy batteries

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