Evanko Presentation

"University of Oregon"Sang-Eun Chun, Shannon Boettcher*""

Oregon State University"Xingfeng Wang, Bao Wang, Vadivukarasi Raju, David Ji*""

University of California, Santa Barbara"Brian Evanko, Nick Parker, Dave Auston, Galen Stucky*"""April 29, 2014"

High Power Capacitors Boosted with Both Anolyte and Catholyte "

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Electrochemical Capacitors

•  High Power Density •  Low Energy Density •  Excellent Cycle

Efficiency, Cyclability, and Lifetime

•  Referred to also as supercapacitors, ultracapacitors, and EDLCs

P. Simon and Y. Gogotsi, “Materials for electrochemical capacitors.,” Nat. Mater., vol. 7, no. 11, pp. 845–54, Nov. 2008.



Traditional Capacitor Supercapacitor

P. Jampani, et al. “Advancing the supercapacitor materials and technology frontier” Electrochem. Soc. Interface, 2010.

- - - -

+ +

+ +

d

A

ε

- +

- +

- + - +

- +

- +



•  Energy stored in a capacitor is proportional to the area under the charge/discharge curve.

+ −

K+

K+

Galvanostatic discharge profiles (1 A/g) of devices with KI and VOSO4 concentrations of І) 0.15 M and 0.1 M, II) 0.3 M and 0.2 M, and III) 0.75 M and 0.5 M, respectively

SO42-

K+

K+ SO42-

K+

K+ SO42-

Electrolyte: Aqueous K2SO4

Specific Energy: 5 Wh/kg


Redox-Active Electrolytes: Gen I Chemistry

•  Redox-active ions in electrolyte generate pseudocapacitance

•  Fast kinetics without material degradation

+ I-

I3-

I- SO4

2-

I-

(+) 3I- → I3- + 2e-

SO42-

− V3+

VO2+

K+

VO2+

K+

VO2+

(-) 2VO2+ + 2e- → 2V3+

Electrolyte: 0.1 M VOSO4 and 0.15 M KI

Galvanostatic discharge profiles (1 A/g) of devices with KI and VOSO4 concentrations of І) 0.15 M and 0.1 M, II) 0.3 M and 0.2 M, and III) 0.75 M and 0.5 M, respectively

Specific Energy: 20 Wh/kg


Redox-Active Electrolytes: Gen II Chemistry

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Electrolyte: 0.1 M methyl viologen, 1 M KBr

•  The methyl viologen bromide system behaves as a capacitor at low voltages and a battery at higher voltages.

•  1.5 V operating window with Br -→ Br3

- oxidation and MV2+ → MV+ reduction greatly increases specific energy.


Redox-Active Electrolytes: Gen II Chemistry

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Potential window 1.0 V 1.2 V 1.4 V

Specific capacity (mAh/g) 8.6 18.9 36.8

Energy density (Wh/kg) 4.6 15.1 36.6

Coulombic (%) 99.3 99.2 98.2

Energy (%) 84.2 89.1 87.0

• Self-‐discharge A#er 6 h of self-‐discharge, 22 Wh/kg is s3ll reserved in Br/MV

* Ac3ve electrode mass-‐based energy density measured from Swagelok-‐cell


Design of Electrochemical Cell

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Epoxy insula3ng layer

separator (filter paper)

Swagelok-‐type cell Volume-‐limi<ng cell

Minimal amount of electrode + electrolyte mass

Side


Scaling Up

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Cell Goals for 18650 Format Redox Supercapacitor

Current Commercially Available Device

Electrolyte Aqueous (1.5V) Organic (2.7V)

Dimensions H: 65mm ; OD: 18mm H: 45mm ; OD: 22mm

Volume 16.5 cm3 17.1 cm3

Specific Energy ≥ 15 Wh/kg 4.4 Wh/kg

Specific Power ≥ 2000 W/kg 7000 W/kg

Temperature -‐10 ºC to 60ºC -‐40ºC to 65ºC


18650 Prototyping Line

•  Electrodes are coated by doctor blade on vacuum chuck with PID controlled IR lamp drying.

•  Roll press installation was completed April 10.

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18650 Prototyping Line

•  We also have received and installed equipment for welding, necking, and sealing 18650 cans.

•  Testing is done in-house, in the remodeled MRL Battery Lab.

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