supercapacitors for hybrid and plug-in hybrid electric vehicles v. r. koch covalent associates, inc....

Supercapacitors for Hybrid and Plug-in Hybrid

Electric Vehicles

V. R. Koch

Covalent Associates, Inc.and

Oregon State University

December 4, 2008

Overview

• What are supercapacitors (aka EDLCs, ultracaps, supercaps)?

• Supercap market segments

• Ionic liquids: new electrolyte materials for high temp supercaps

• Supercap performance at elevated temps

• Summary

• Postscript from the Port of Yokahama

Types of Capacitors

0.01

0.1

1

10

100

1000

10 100 1000 10000

Energy Storage Devices

Supercap Hardware

AA size cell

2325 coin cell

Supercapacitor Test Bank

Fuji Heavy Industries (Subaru) has purchased the Electric Double Layer Capacitor (supercapacitor) business from Kanebo Ltd for an estimated •100 million yen, according to reports in the Japanese business press (August 2008).

Fuji Heavy Industries plans to start commercial production of the ultracapacitor device before the end of 2010, and to sell the product to other companies, in addition to using it for its own vehicles.

Why Supercaps for EV/PHEV?

EDLC Market Segments as f(T)

-80oC

-60oC

-40oC

-20oC

0oC

20oC

40oC

60oC

80oC

MilitaryAuto

Consumerelectronics

Available supercap thermal envelope: -30ºC to 65ºC

Supercaps for EV and PHEV

• Non-aqueous electrolytes fail at temps as low as 65ºC owing to thermal decomposition reactions.

• Supercap modules in hybrid EVs experience operating temps as high as 125ºC.

• New thermochemically stable electrolytes are required to enable supercap performance at elevated temps over long periods of time.

• Such electrolytes incorporate ionic liquid materials.

www.covalentassociates.com

www.covalentassociates.com

www.covalentassociates.com

• ILs are materials composed solely of anions and cations.

• Molecular solvents are composed of neutral species benzene, propylene carbonate, water

Negative (-) Positive (+)

Ionic Liquids

HO

HO O

O

N

N+

S

N+

N

N+N

N

N+

Imidazolium Pyrazolium

ThiazoliumO

N+

Oxazolium

Triazolium

N+

N+N

Pyridinium

Pyridazinium

N+

N

Pyrimidnium

N+

N

Pyrazinium

Cation Structures

Inorganic Organic

BR4- Sulfonate

-O-(SO2R)

PR6- Imide

-N-(SO2R)2

Methide -C-(SO2R)3

Anion Structures

R = halide, perfluoroalkyl and other electron withdrawing alkyl or aryl substituents

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Critical Thermal Stability

0

20

40

60

80

100

120

0 100 200 300 400 500 600 700

T/oC

Weig

ht

Loss (

%)

PC

EMIIm

N N (CF3SO2)2N-No volatility

High thermal stability

O O

O

bp 240ºC

Electrolyte Storage: 150oC for 2 hr

Ionic Liquid 1M TEABF4/PC

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Supercap Cycle Life: 150oC at 1.75V

0

10

20

30

40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

cycle #

Ca

pa

cit

an

ce

(F/

g)

Ionic Liquid

1M TEABF4/PC

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IL data represent 42 daysof continuous cycling at 150ºC

Summary

• A new family of non-flammable and thermochemically stable ionic liquid electrolytes has been developed.

• Such electrolytes enable supercapacitor performance at temperatures in excess of 150ºC.

• We are working with device manufacturers to bring safe, high temperature supercaps to the auto industry.