1 m

Polymer Separator Films

for Lithium Ion Batteries

Patrick Brant

ExxonMobil Chemical Company

Carnegie Mellon University

Pittsburgh, PA

November 11, 2009

2

Overview

ExxonMobil organization

Polyolefin utility

Lithium ion batteries and separator film

Summary

3

4

POs – Key Features

Polyolefins (POs) – Champions of Thermoplastics a

• Chemically Inert

• Low cost

• Recyclable / Energy

Recovery

• Exceptional Fabrication &

Applications Versatility

• WW Production of Thermoplastics > 350 Billion Pounds / Year

• POs > 50% of all Thermoplastics

• Sustainable? 6-7%, CO2 [2 saved/1 produced] b, downgauging

Paper or plastic? 4x more

POs54%

PS 9%PVC17%

PET 5.0%

ABS3.5%

PU

5.5%

PA1.3%

PMMA0.9%

PC0.9%

a G. Gottfreid, Polymeric Materials, Ch. 1

b McKinsey and Company study, reviewed

by the Öko Institute

Others

5

Polyolefins in Transportation

About 200 lb of plastics, rubber in typical car

10% Weight Reduction –

6.6% Fuel Economy

Advanced motor oils

6

Lithium Ion Battery Overview

Past Present

Initial motivation for work

Battery components and brief history

Separator structure and functions; how they are made

Lithium ion battery benefits, impact

Future

Drivers

Opportunities

EV, HEV, pHEV considerations

Summary

7

Initial Motivation for Work

Two clear fundamental advantages

1. Lithium is the lightest metal

2. Lithium half reaction standard electrode potential is big †

In principal, fundamental advantages could lead to

Higher energy density; weight and volume advantage

Higher power density at a given energy density

Fewer cells, related parts

Key Hurdles- beginning in 1975

Cathode

Anode

Electrolyte

Separator

Self-discharge performance

Memory

Cost per W-h and per W

Abuse resistance

Cold/hot behavior

Thermal management (safety)

Cycle life

Markets?† “Electrochemical Series” in Handbook of Chemistry and Physics

Ragone Plot

1

10

100

1000

10000

1 10 100 1000

Specific Energy (Wh/kg)

Sp

ec

ific

Po

we

r (W

/kg

) LIB

Other

Battery

Options

* 1 Wh = 3,600 J or 860.4 cal

Ma

teria

lsP

erf

orm

an

ce

8

Basic Components in (Lithium Ion) Battery

* Separator = Battery Separator Film = BSF

Separator *

AnodeCathode Electrolyte

Graphitic Carbon + Binder

Lithium Metal Oxide+ Binder

e-

Galleries for Li Colle

cto

r Colle

cto

r

9

Brief History

Other Cathodes:

Li(Ni,Mn,Co)O2

Li(Ni,Co,Al)O2F. Beguin and R. Yazami, Actualite Chimique 2006 295-296, 86-90

10

Separator Film Requirements

Permeable (~40-50% void volume) for ready ion

transport, yet insulate electrodes

Small pores (seive) but low resistance

Chemically inert, uniform, free of flaws

2-10+ years in highly reactive environment

Excellent puncture strength

Thin (7-30μ), dimensionally stable

Slitting, compatible w/ manufacturing equipment

Act as safety device if cell becomes too hot

Safety margin: Δ = [meltdown temperature –

shutdown temperature]

The higher the meltdown temperature the better

Lithium dendrite

Porosity

yTortuousiteffR

11

Polyethylene – A High Performance Thermoplastic

C

C

C

C

C

H H

H H

H H

H H

H H

Battery Separator Film

Tg -120C Tm 132-140C

12

How to Make a Classic Monolayer Separator Film

Pennings et al, 1965 - 1979: Gel spinning and super drawing of uhmw HDPE filaments

Solution of polyethylene dissolved in hydrocarbon

Gel sheetThin wall cellular structure composed

of stacked lamella crystals

Micro-porous filmUniform fine fibrous network

composed of stacked lamella crystals

Biaxially

orient,

extract liquid

hydrocarbon,

dry

1 m 5 m1 mSEM SEMTEM TEM5 m5 m

Collapse of

cell

Fibrillation of

plane stacked

lamella crystal

CellSchematic

diagram

~ 1 m ~10nm

AFM 1 m

13

A Closer Look at Separator Morphology

TEM’s of stained cross-sections show highly uniform, finely textured morphology

TD x ND plane MD x ND plane

Crystalline lamellae

14

Orientation and Crystallinity *

Sample 1: 2 % UHMWPE

0

50

100

150

200

250

300

350

400

450

8 13 18 23

2 (o)

I(2

) (a

.u)

WAXS of a BSF

(110)

(200)

b

c

a

ORTHORHOMBIC

UNIT CELL:

a = 7.36 Å

b = 4.92 A

c = 2.54 Å; chain axis

ab

(110)

(200)

* Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the

U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-

AC02-98CH10886

b

CHAIN FOLDED

CRYSTALLINE

LAMELLAE ª

NONCRYSTALLINE

POLYMER

ª Some extended chains

15

Realizing the Benefits of Lithium Ion Batteries

Higher energy density - nearly 2x higher than Ni-MH; weight advantage Higher power density at a given energy density

Higher voltage - ~3.6 V vs 1.2 V for Ni-Cd and Ni-MH; fewer cells, connections

Better self-discharge performance - around one tenth of Ni-Cd and Ni-MH

Virtually no memory effect

Expect lower cost per W-h and per W Raw material cost can be a big factor

Other key data: Abuse resistance

Cold/hot behavior (-40 to +40C); electrolyte viscosity

Thermal management

Cycle life

16

0

0.5

1

1.5

2

2.5

3

1975

1980

1985

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Annu

al C

ell P

rodu

ctio

n, 1

0^9

Year

Growth of LIB Comes with Increasing Demands

Markets: Cellphone, laptop, camcorder, digital camera, power tool, ebikes,…

Increasing capacityDowngauging / higher strength

HEV

Early Li-ion

Battery at EV show

Chicago, ‘77

Invention of

microporous

PE separator

Separator used in

world’s first LIB

1

2

3

1990 1995 2000 2005 2010

Ah

EV

Electrovaya’s Maya-300

220 Ah14 Ah1 Ah 4000+ Ah70 Ah

17

Future – Continuing Growth

Energy and LIB

Opportunities, challenges

EV, HEV, pHEV considerations

Evolving demands on separator

Economy Security

Climate

6 x109 Tons CO2/year

Energy

WSJ, August 6, 2009

18

Global Economics and Energy

0

2

4

6

8

10

1980 2030 2005

0

25

50

75

100

1980 2030 2005

0

50

100

150

200

250

300

350

1980 2030 2005

billion

population GDP energy demandtrillion 2005$ MBDOE

Average Growth / Yr.

2005 – 2030

0.9%

Average Growth / Yr.

2005 – 2030

3.0%

Average Growth / Yr.

2005 – 2030

1.2%

19

Transportation - Global

Power

Generation

1.6%

Res/Comm

0.4%

Industrial

1.0%

Transportation

1.4%

84.540.4

124.0

61.5

2030: ~310 MBDOE

1.2%

demand by sector

2030 demand in MBDOE

Average growth/Yr 2005-2030

0

10

20

30

40

50

60

70

1980 2005 2030

Light-Duty

Vehicles

Heavy Duty

Aviation

Marine

Rail 0.7%

2.5%

0.3%

2.0%

1.9%

0

10

20

30

40

50

60

70

1980 2005 2030

Light-Duty

Vehicles

0.3%

global transportation

by sub-sector

MBDOE Average Growth / Yr.

2005 – 2030

1.4%

20

Energy Consumption and Productivity

21

Gasoline ~ 25 cents / gallon

22

Batteries in Transportation

100

101

102

103

104

105

106

107

Specific

Pow

er

(W/k

g)

0.01 0.1 1 10 100 1000

Specific Energy (Wh/kg)

Capacitors

Batteries Fuel

Cells

Combustion

Electrochemical

Capacitors

Engines

Ele

ctr

oly

tic

Ragone Plot

LIB

Gasoline LIB

Energy Density,

kWh† /kg

13 a* 0.17 *

Energy Efficiency ~15-20% * 85-90% *

Efficiency of

Producing Fuel

0.9 ~0.4-0.5 b

Diversification and more efficient use of hydrocarbons: 13.8 MBbl oil/day for transportation in US

Reduce carbon dioxide emissions

Part of integrated set of solutions

a 3x the energy density of sugarb For production of e- from coal or NG † 1 kWh = 3,600 kJ or 860.4 kcal

Gasoline versus LIB

* Deutsche Bank, Auto Manufacturing Electric Cars: Plugged in, 9 June 2008

23

Relative LIB Benefit / Cost

Rough estimate: LIB size for EV ~200 kg (80 – 1000 V)

% of Work Done by

Batteries

[Be

ne

fit

/ C

os

t]

1 = break even

high

energy

high

powerHEV

EV

Drive Cycle

Ve

locity

IC

EV = 100% of cycle

HEV < 100%

Energy capture

24

Evolving Separator Demands

Higher temperature stability - ~ 200 250+C

Retain sufficient dimensional stability

Coatings and higher temperature polymers

• Blends, co-extrusion

Increasing puncture resistance

w/ appropriate permeability

Lower shutdown temperature

~10+ year life

Delivered flawlessly at lower cost

for larger battery formats (stacked, prismatic), and

bigger battery packs…. but emphases vary according

to LIB chemistry and module or pack control

Co-extruded Separator

Monolayer

Wet

Process

Coex

Technology

Polymer

Design

25

Improved Thermal Stability

: E25MMS (mono-layer)

: New Commercial Grade (co-extruded)Permeability

Puncture

Thermal

Stability

Shutdown

Temperature

Meltdown

Temperature

Power

Mechanical

Safety

Thermal

Safety

Tensile

Balance

New commercial grade has superior thermal stability, higher permeability

and meltdown temperature than standard mono-layer

26

Lower TD Shrinkage

TD Shrinkage

0

10

20

30

40

E25MMS V25EKD V25CGD Developmental grade 1

Grades

% s

hri

nk

ag

e

TD shrinkage at 105'C, 8 hrs TD shrinkage at 130'C, 30mins

Lower TD shrinkage allows

more flexible LIB designs

27

Summary

Lithium ion batteries power the portable electronics revolution

Polyolefin separators a key part of this success story

Lithium ion batteries for transportation: ebikes, EV/p-HEV, HEV

Major commitments already

• Battery and auto manufacturer announcements

Continuing improvements, especially to reduce cost, increase life

• Once again, separators critical to performance

Can be a key part of overall drive to increase energy efficiency

Uninterrupted power supplies

Fixed energy storage

More technology breakthroughs are critical

Exciting research and development opportunities

28

Thank you

Many contributors to this talk

JoAnn Canich, Alan Vaughan

Koichi Kono, Jack Tan, Takeshi Ishihara, Jeff Brinen, Zerong Lin, …..

29

Shutdown Performance

0

50

100

150

200

100 110 120 130 140

Temperature / oC

Perm

eabili

ty (

rela

tive)

D evelopm entalgrade 2

V25EKD

Developmental grade 2 is designed for earlier pore closure with complete

shutdown at 128˚C, potentially prevent exothermic reaction which leads

to thermal runaway in the event of internal shorts or overcharging

30

Economics Lesson: Hybrid Sales Linked to Fuel Price

U.S. Gasoline Price and Hybrid Sales (2004-2008)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

Jan-0

4

Mar

-04

May

-04

Jul-0

4

Sep-0

4

Nov-

04

Jan-0

5

Mar

-05

May

-05

Jul-0

5

Sep-0

5

Nov-

05

Jan-0

6

Mar

-06

May

-06

Jul-0

6

Sep-0

6

Nov-

06

Jan-0

7

Mar

-07

May

-07

Jul-0

7

Sep-0

7

Nov-

07

Jan-0

8

Mar

-08

May

-08

Ga

so

lin

e P

ric

e (

$/g

al)

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

N.A

. M

on

thly

HE

V S

ale

s

Gas Price HEV Sales

US accounts for ~70% of all HEV sales