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