Department of Materials Science and Engineering

Supercapacitors:Supercapacitors:Decreasing Resistance Through

Tape Casting

Submitted to Dr. Yury Gogotsi, John Chmiola, and the Drexel University Engineering Faculty

Dan Berrigan – DREAM Fellow

Department of Materials Science and Engineering

Overview

Motivation- Impending Oil Crisis- Uses in Hybrid Vehicles

Introduction- Supercapacitors- Making the electrode- Problems with current method

GoalsTape Casting

- Problems encountered- Overall solution

Future Work

Department of Materials Science and Engineering

Motivation

• Impending Oil Crisis– Rising costs of Crude Oil– 70% of oil goes to transportation– China becoming increasingly

modernized• Hybrid Electric Vehicles

– Batteries supply bursts of power to a gasoline engine

– Temporary solution to slow oil consumption

Cars like Honda’s Civic Hybrid, if widely accepted can reduce the dependence on foreign oil.www.honda.com

Problems with Batteries

• Low power density and add weight

• Increase the cost of the car

• Lose 20% of the energy put into them

Thermoanalytics. (2001). Battery Types and Characteristics. 2004.

Department of Materials Science and Engineering

The Super Solution

Chmiola, John. “Supercapacitance Measurements of Porous Carbon Obtained Through Chlorination of Metal Carbides.” Senior Design Drexel U., 2004.

• Works by charge separation of an electrolytic solution with a non-interacting electrode

• Cheaper and easier to produce

• Higher power density

• Completely reversible reaction

• Higher capacitance than traditional capacitors

Pores in the Carbide Derived Carbon allow ions of sulfuric acid to gather inside the electrode when a voltage is applied to the supercapacitor.

Department of Materials Science and Engineering

Building the Supercapacitor

Chmiola, John. “Supercapacitance Measurements of Porous Carbon Obtained Through Chlorination of Metal Carbides.” Senior Design Drexel U., 2004.

Schematic showing the components of a test cell

Department of Materials Science and Engineering

Making the Electrode

Chmiola, John. “Supercapacitance Measurements of Porous Carbon Obtained Through Chlorination of Metal Carbides.” Senior Design Drexel U., 2004.

Several problems were inherent to this process: the mix of binder and carbon was not homogeneous, the electrode is not in complete contact with current collector, and it is patented already.

Department of Materials Science and Engineering

Goals

2

2V

R

CP

• Invent a process that decreases the resistance between the current collector and the electrode

• Decrease the resistance inside the carbon electrode

Ti2AlC@1000C

020406080

100120140160180200

MW

NT [1]

SWNT [2]

fb-MW

NT [3]

a-C [3]

C cloth [4]

B4C@1000C

Cap

acit

ance

(F

/g)

Previous work found that Ti2AlC had a higher specific capacitance than carbon nanotubes. However, the high resistances makes the power much less.

Department of Materials Science and Engineering

Tape Casting

→

→

A slurry of carbon, NMP solvent, and PVDF binder is made.

The slurry is deposited on electrodes and a doctor’s blade is passed over it.

The electrodes are heated in an oven to evaporate the solvent.

Department of Materials Science and Engineering

Tape Casting Process

1) Use mortar and pestle to grind the carbon grains for 10 minutes.

2) Weigh the carbon and 5 wt% of polyvinylidene fluoride (PVDF) in separate containers.

3) Mix in with a pipette solvent, N-Methyl-2-Pyrrolidone (NMP) — enough to the carbon to make it into a thick paste. In the other container, add enough solvent to completely dissolve the PVDF.

4) Sonicate both for 10 minutes.

5) Add the PVDF and solvent to the carbon and mix for 15 minutes. If the slurry has a low viscosity, then heat it at a temperature between 80-100 °C during mixing.

Creating the Slurry

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Problems Encountered

• Must have viscosity of maple syrup

• Must be free of lumps

• Must be cast directly onto electrodes

Solved by careful moderation of solvent.

Solved by mixing carbon with solvent and binder with solvent separately, then sonicating for 10 minutes.

Solved by drilling holes into a wooden board.

Department of Materials Science and Engineering

Tape Casting Process

1) Wrap electrode edge in masking tape.

2) Slide it into a hole in the wooden board.

3) Deposit a small amount of slip (2-3 drops) using a pipette.

4) Pass doctors blade over electrode.

5) Bake in ~100°C oven for 20 minutes.

Casting the Electrode

Department of Materials Science and Engineering

Future Work

• Carbon nanotubes• Metal powder (Cr, Al)• Different binder (Teflon, PVDC)• Electrochemical Analysis of the

Samples• Improve Final Tape Properties

Department of Materials Science and Engineering

Acknowledgements

John Chmiola

Dr. Yury Gogotsi

Dorilona Rose

DREAM Program

Drexel University

Department of Materials Science and Engineering

References

Chmiola, John. “Supercapacitance Measurements of Porous Carbon Obtained

Through Chlorination of Metal Carbides.” Senior Design Drexel U., 2004.

Singer, Clifford. “Energy Usage.” http://acdisweb.acdis.uiuc.edu/NPRE201/fall02web/lectures_pdf/lecture03.pdf. 4 Sept. 2003.

Thermoanalytics. (2001). Battery Types and Characteristics. 2004.