Innovative Cell Materials and Design for 300 Mile Range EVs

Yimin Zhu, PD/PI Nanosys, Inc Palo Alto, California May 13 ~17, 2013

DOE Vehicle Technologies AMR 2013

ES130_zhu_2013_p This presentation does not contain any proprietary, confidential, or otherwise restricted information

• Start: Oct. 1st, 2011 • End: Sept. 30th, 2014 • 40% complete

• Barriers addressed – Performance: Low Wh/kg & Wh/L – Life: Poor deep discharge cycles – Cost: High $/kWh

• Targets Anode: >700 mAh/g 1,600 mAh/g >800 cycles

Cathode: 250 mAh/g >260 mAh/g >800 cycle

Cell: 350 Wh/kg 800 Wh/L

Project Objectives

Anode: Develop a 700~1600 mAh/g Si anode (SiNANOdeTM) toward >800 cycles - Demonstrate 700~1000 mAh/g SiNANOde toward >800 cycles - Demonstrate SiNANOde with an electrode loading of 3~6mAh/cm2 - Demonstrate SiNANOde with 1600 mAh/g

Cathode: Develop a 260 mAh/g cathode (Mn-rich) toward >800 cycles - Improve 250~260 mAh/g cathode with capability to meet >800 cycles - Improve cathode electrode loading and power

Cell: Develop unique cell combining SiNANOde with >250 mAh/g cathode to eventually

achieve 350 Wh/kg and 800 Wh/L, resulting in

Project Milestone

Milestones in the period of Apr. 2012 ~ Mar. 2013: - Baseline SiNANOde Cycle Life Demonstration - SiNANOde Specific Capacity Improvement: Increase to 700~1600mAh/g and improve cycle life - Optimization of cathode composition - Scale-up SiNANOde manufacturing process

Overall Project Milestone Status Kick off meeting 10/26/11 Completed 1st quarterly report 1/31/12 Completed Initial Specifications Complete 10/31/11 Completed Material Properties Modeled 12/30/11 Completed Anode material batch deliveries and characterization Multiple On track Cathode material batch deliveries and characterization Multiple On track Test Cell Multiple On track Delivered 18 cells with high energy density on Nov. 30th, 2012 On track Systems Integration Design 9/31/12 On track Test Reports Delivered to DoE Multiple On track 4

SES Drop-In Anode Solution

Volume production process using graphite as direct substrate for Si nanowire growth – Cost effective and high Si utilization – Improves dispersion within slurry and drop in process – Si-C conductivity improvement – Si% or anode specific capacity is controllable, focusing on 500 ~ 1600 mAh/g – High electrode loading, i.e. 1.5g/cm3 – Good cycling performance, cycled >1000 times

Similar feel to graphite, e.g. tap density similar to

graphite powder substrate High Capacity

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SES SiNANOde Approach vs. Hollow/Porous Approach

Advantages

Overcome Potential Disadvantages SES SiNANOde Hollow/Porous

Better accommodation of cycling strain High surface area leads to higher self discharge & poor cycling performance

Low A/V & Intact NW after cycling High A/V; defects Unique conversion reactions

High interfacial charge transfer rates Low pack density and low volumetric energy density

Pack density similar to graphite

Pack density lower than graphite Short tunneling length for electronic

transport

Short diffusion length for ionic transport Hard to be mass-produced Mass-produced with a competing cost * high Si utilization

Difficult and expensive to commercialize

SES Exploit Advantages & Defeat Potential Problems of Si Nano-materials

Nanowire Length

Particle

The nanowire has lower surface area/volume ratio, A/V, and hence less side-reaction with electrolyte and better cycle life

Surface Area/Volume Ratio

0.00.10.20.30.40.50.60.70.80.91.0

0 200 400 600 800 1000Length, nm

A /

V

Nanowire 50Spherical Particle 50Nanowire 100Spherical Particle 100Nanowire 200Spherical Particle 200

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Cathode Approach

Cathode Development Cathode materials currently being used in PHEVs and EVs have a maximum capacity of ~ 150

mAh g-1 or less. Mn-rich composite cathode, can deliver an initial capacity >250 mAh g−1, expected to be

significantly stable in non-aqueous electrolytes. The high operation voltage electrolyte is being developed

• Mn-rich cathode materials (>250 mAh/g) are screened to have an attractive cathode and combine with SiNANOde

• Mn-rich cathode material surface is modified by oxide or other components to improve its electrochemical performance and stability

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Cell Development Approach

Combining the attractive cathode feature with a high-capacity SiNANOde to accomplish our cell development objectives

Mn-rich cathode materials showed a reversible specific capacity as high as 268mAh/g

Full cell with high specific capacity SiNANOde showed an ICE of >91% and anode’s reversible specific capacity of 1600mAh/g

High Specific Capacity SiNANOde

3.03.13.23.33.43.53.63.73.83.94.04.14.2

0 300 600 900 1200 1500 1800Specific Capacity (mAh/g)

Volta

ge (V

)

8

0 50 100 150 200 250 300 3502.0

2.5

3.0

3.5

4.0

4.5

Sample 1 Sample 2 Sample 3 Sample 4

Volta

ge (V

)

Capacity (mAh/g)

Formation Profile

0 50 100 150 200 250 300 3502.0

2.5

3.0

3.5

4.0

4.5

Sample 1 Sample 2 Sample 3 Sample 4

Volta

ge (V

)

Capacity (mAh/g)

Formation Profile

SiNANOde Full Cell vs. Graphite Full Cell

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 50 100 150 200 250 300 350

Cycle Number

Nor

mal

ized

Dch

g C

apac

ity

SiNANOde CellGraphite Cell

Technical Achievement - Anode

Full cells with a baseline cathode (LCO) & a SiNANOde exhibited ~350 cycles at ~76% capacity retention, which still showed much higher anode-specific capacity over graphite anode. An improved LCO cathode is showing better full cell performance (ongoing)

SiNANOde (Green) OUTPERFORM commercial Si nanopowder (Blue) with identical diameter due to its much lower surface area/volume ratio, better dispersion in slurry and conductivity

100%DOD Cycling

Full cells w/ identical Si%: Nanowires vs. nanopowders

200250300350400450500550600650

0 20 40 60 80 100 120 140 160Cycle

Cap

acity

, mA

h/g

NanopowderNanowire

9

Technical Achievement - High Capacity Anode: Cycle Life

- Increased the specific capacity of SiNANOde up to 850mAh/g by controlling Si nanowire content. - Continuously improving the conductivity of SiNANOde and further optimizing the SiNANOde material, which has showed longer anode cycling life of ~510 cycles at 83% capacity retention at 0.3C. - At beginning the cell has been used for various C-rate testing.

200

300

400

500

600

700

800

900

1000

1100

1200

0 50 100 150 200 250 300 350 400 450 500

Cycle

Cap

acity

, mA

h/g

10

Technical Achievement - High Energy Density Pouch Cell Performance

- The 8%SiNANOde pouch cell has already showed the volumetric energy density >620Wh/L in conventional 4.2 ~3.0V. - The mid-voltage is ~3.7V.

Discharge C-rate

Energy Density Wh/L

C/10 627 C/5 616 C/3 582

SiNANOde

Graphite

Calendered Anode ~1.5g/cm3

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Technical Achievement - SiNANOde Full Cell Voltage Profile

- The voltage profile for the full cells showed a typical slope-like charging behavior between 3.0 and 4.2V though there is a shoulder between 3.8 and 3.9V. - During discharging a clear plateau around 3.4~3.5V can be attributed to Si capacity contribution - The full cells can be used in a typical voltage range of 3 ~ 4.2V

12

Technical Achievement - Less Voltage Hysteresis for SiNANOde

The hysteresis effect is less pronounced for 8%SiNANOde/LCO full cell in comparison with 8%Si power-graphite/LCO full cell 13

Voltage Hysteresis

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4.0

4.1

4.2

0 10 20 30 40 50 60 70 80 90 100SOC (%)

OC

V_3h

rs (V

)

SiNANOde Chg SiNANOde Dchg

Si Powder-Gr Chg Si Powder Dchg

Prior to cycling 10th cycle 100th cycle

Technical Achievement - SEM Characterization of Si Nanowires/Current Collector Post Cycling

• Si nanowire deforms to fill void areas in carbon anode material matrix

• Si nanowire remains intact and fully functional after 100% DoD cycling

• Thin SEI formed on Si nanowires 14

-C1.1 cell showed higher coulombic efficiency and better cycling performance than C1 cell

96.0

96.5

97.0

97.5

98.0

98.5

99.0

99.5

100.0

0 20 40 60 80 100 120 140 160 180 200

Cycle

Cou

lom

bic

effic

ienc

y, %

C1

C1.1

050

100150200250300350400450500550600650700

0 50 100 150 200 250

Cycle

Ano

de d

elith

iatio

n ca

paci

ty, m

Ah/

g

C1

C1.1

C1.1 C1

- In C1: the Si nanowires in the composite can be deteriorated faster and formed thicker SEI - In C1.1: thin SEI or less decomposed electrolyte buildup on Si nanowires in the composite

Technical Achievement - SiNANOde SEI in SES’s C1 & C1.1 Electrolyte

15

Technical Achievement - Cathode

- Mn-rich cathode materials, in-house and commercial ones, were screened for an optimal one (>250 mAh/g) to be combined with SiNANOde. - Charge/discharge of the Li/Mn-rich cathode half cell in 4.6-2.5V at room temperature - Surface modification has been tried to improve the cathode materials.

0 50 100 150 200 250 300 3502.0

2.5

3.0

3.5

4.0

4.5

Sample 1 Sample 2 Sample 3 Sample 4

Volta

ge (V

)

Capacity (mAh/g)

Formation Profile

- Identification of a high voltage electrolyte is very critical in enhancing its cyclability. - The effect of electrolyte composition on the cyclability: Cell #2 used an electrolyte tailored to have high voltage stability.

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0 5 10 15 20 25 30 35 40 45 5050

75

100

125

150

175

200

225

250

275

0.1C

0.5C

2C1C

Sample B Sample ADi

scha

rge

capa

city

(mAh

/g)

Cycle

0.5C

Technical Achievement - Cell Development

The cathode material surface has been modified, which has enhanced its C-rate performance.

40%

50%

60%

70%

80%

90%

100%

0 25 50 75 100 125 150Cycle

Dis

char

ge C

apac

ity

400Wh/kg

The 400 Wh/kg-designed cell made manually is cycled at 0.3C. The capacity is initially fading faster, showing 55% retention at 150th cycle

SiNANOde 600 mAh/g 800 mAh/g 1200 mAh/g

Processable in plant 4.4 V 225 Wh/kg 240 Wh/kg 255 Wh/kg

Unprocessable in plant 4.4 V

(~1300 mg/25 cm2) 255 Wh/kg 275 Wh/kg 300 Wh/kg

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To make pouch cells of SiNANOde/Mn-rich cathode in plant, the cell fabrication has been developing to achieve high energy densities and improve its processablity (ongoing)

Technical Achievement - Cell Development

1.3 Ah Baseline Cell with 500~600 mAh/g Anode and LCO cathode, achieved >260 Wh/kg and >600 Wh/L

0

200

400

600

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1400

0 50 100 150 200Cycle

Dis

char

ge C

apa.

/ m

Ah

0

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40

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0 50 100 150 200Cycle

Dis

char

ge C

apa.

/ %

The cell is Cycled at 0.5C rate (DOD 100%)

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- The lithium is provided by LCO cathode - Anode potential is controlled by using Lithium metal reference electrode - The cell shows high coulombic efficiency of 99.5~100% - The cell gives a beginning capacity of 490mAh/g and stabilizing around 400mAh/g over 300 cycles if anode potential is in the range of 10~700mV.

Technical Achievement - Cell Development

LCO/8%SiNANOde/Li Three Electrodes Pouch CellLCO/8%SiNANOde/Li Three Electrodes Pouch CellLCO/SiNANOde/Li Three Electrode Pouch Cell

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Thickness change of High Energy Density Pouch Cells: SiNANOde/LCO after 300 cycles

- Pouch cells have showed acceptable cell thickness change, < 14% cell swelling over 300 cycles.

SiNANOde/LCO Pouch Cell (500mAh): 4.2~3V

0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 300 350Cycle Number

Cel

l Sw

ellin

g, %

SiNANOde/LCO Pouch CellSiNANOde/LCO Pouch Cell (500mAh): 4.2~3V

0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 300 350Cycle Number

Cel

l Sw

ellin

g, %

SiNANOde/LCO Pouch Cell

Technical Achievement - Cell Development

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Superior full cell performance at high electrode loading

• SiNANOde 18650 full cell shows >1000 cycle 80% retention at 0.5C cycling though it fades faster in the first 50 cycles

0.000.100.200.300.400.500.600.700.800.901.00

0 150 300 450 600 750 900 1050Cycle #

Nor

mal

ized

Cap

acity

Technical Achievement - 18650 Cell Development

21

Self discharge and subsequent recharge is comparable (~1% less) than commercial graphite

Condition

8% Si-Composite /LCO Normalize to

Graphite/LCO Control Retention % @20oC at end of 1 month 99.6% Realized capacity upon recharge after discharging at 20oC for 1 month 98.7% Retention % @60oC at end of 1 week 98.7% Realized capacity upon recharge after discharging at 60oC for 1 week

99.3%

Technical Achievement - Cell Development

22

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Collaborations

-LG CPI (Industry, within the VT program) -LGC (Industry, within the VT program) -Dow Kokam (Industry, within the VT program) -EaglePicher (Industry, outside the VT program) -AMAT (Industry, outside the VT program) -ANL (US DOE Laboratory, outside the VT program) -LBNL (US DOE Laboratory, outside the VT program) -University of California, Berkeley

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Future Work Focus on achieving high energy density and enhanced cycle life Cycle Life Enhancement for 700~1000 mAh/g Anode - Pilot-scale manufacturing quantities of SiNANOde product - Cost-sensitivity modeling - Optimize the SiNANOde and appropriate binders - Develop electrolyte additives to improve cycle life - Electrochemical analysis Enhanced Si Capacity 1,600 mAh/g Anode - Improve battery discharge rate performance - Achieve high electrode loading - Achieve a reversible specific capacity of 1,600 mAh/g Optimization of Cathode Composition and Cell Components - Optimize the cathode material composition - Minimize inactive components in the cell - Address cathode electrode activation during cell formation cycles - Evaluate the compatibility of the developed electrolyte - Improve the cell design to achieve high energy density and long cycle life - Integrate the new binder and electrolyte and cell formation/testing protocol

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Summary

Summarized achievements: Anode Targets: 700-1000 mAh/g >800 cycles Anode Achievement: 700~1600 mAh/g >510 cycles (ongoing) Cathode Targets: 250 mAh/g >800 cycle Cathode Achievement: >250 mAh/g >200 cycles (ongoing) Battery Targets: 350 Wh/kg 800 Wh/L 92%. - Almost 100% utilization of Si capacity has been realized in the cells. - We demonstrated > 510 cycles at 83% retention in coin cell using 700~1000 mAh/g SiNANOde. - We demonstrated good cycling performance of >300 cycles (baseline SiNANOde/LCO) or ~1000 cycles (baseline SiNANOde/NCA). - We achieved a reversible specific capacity of 255 mAh/g for cathode and improved its C-rate performance from 0.2C to >0.5C even at high loading. - Pouch cells achieved 300~400Wh/kg with 1200mAh/g SiNANOde and 255mAh/g cathode. - Pouch cells achieved 260Wh/kg and 600Wh/L with 550mAh/g SiNANOde and LCO cathode. We delivered 18 cells to U.S. DOE for evaluation. - SiNANOde development has been extensively explored on various graphite, which will lead to a cost effective production.

Acknowledgements • Team Battery at Nanosys (Silicon

Energy Storage) and LGCPI/LG Chem.

• Support from the U.S. Department of Energy

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Innovative Cell Materials and Design for 300 Mile Range EVsSlide Number 2Project ObjectivesProject MilestoneSES Drop-In Anode SolutionSES SiNANOde Approach �vs. Hollow/Porous Approach Cathode Approach Cell Development ApproachTechnical Achievement�- Anode Slide Number 10Slide Number 11Slide Number 12Slide Number 13Technical Achievement�- SEM Characterization of Si Nanowires/Current Collector Post CyclingSlide Number 15Technical Achievement�- CathodeTechnical Achievement�- Cell Development Technical Achievement�- Cell Development Slide Number 19Slide Number 20Superior full cell performance at high electrode loadingSelf discharge and subsequent recharge is comparable (~1% less) than commercial graphiteCollaborationsSlide Number 24Slide Number 25Slide Number 26Slide Number 27Responses to Previous Year Reviewers’ CommentsPublications and PresentationsCritical Assumptions and Issues – Reviewer Only