Supercapacitors:

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					                    Department of Materials Science
                           and Engineering



               Supercapacitors:
        Decreasing Resistance Through
                Tape Casting

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

            Dan Berrigan – DREAM Fellow
                                         Overview
                         Department of Materials Science and Engineering



Motivation
   - Impending Oil Crisis
   - Uses in Hybrid Vehicles
Introduction
   - Supercapacitors
   - Making the electrode
   - Problems with current
   method
Goals
Tape Casting
   - Problems encountered
   - Overall solution
Future Work
                                                                    Motivation
                                                  Department of Materials Science and Engineering



• 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                                   Cars like Honda’s Civic
          consumption                                                      Hybrid, if widely accepted
                                                                           can reduce the dependence
    Problems with Batteries                                                on foreign oil.
                                                                           www.honda.com
• 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.
                                                 The Super Solution
                                                   Department of Materials Science and Engineering



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

Chmiola, John. ―Supercapacitance Measurements of Porous Carbon Obtained
 Through Chlorination of Metal Carbides.‖ Senior Design Drexel U., 2004.
          Building the Supercapacitor
                   Department of Materials Science and Engineering




Schematic showing the components of a test cell

Chmiola, John. ―Supercapacitance Measurements of Porous Carbon Obtained
  Through Chlorination of Metal Carbides.‖ Senior Design Drexel U., 2004.
                           Making the Electrode
                               Department of Materials Science and Engineering




                                               
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.
           Chmiola, John. ―Supercapacitance Measurements of Porous Carbon Obtained
             Through Chlorination of Metal Carbides.‖ Senior Design Drexel U., 2004.
                                                      Goals
                      Department of Materials Science and Engineering


                                                200
                                                180




                                 Capacitance (F/g)
                                                160

        C V2
                                                140
                                                120
     P                                         100
                                                 80

        R 2                                      60
                                                 40
                                                 20
                                                  0




Previous work found that                             • Invent a process that
Ti2AlC had a higher specific                         decreases the resistance
capacitance than carbon                              between the current collector
nanotubes. However, the                              and the electrode
high resistances makes the
                                                     • Decrease the resistance
power much less.
                                                     inside the carbon electrode
                                             Tape Casting
                                   Department of Materials Science and Engineering




                                        →

A slurry of carbon, NMP solvent,                  The slurry is deposited on electrodes and
and PVDF binder is made.                          a doctor’s blade is passed over it.




                  →

             The electrodes are heated in an oven to evaporate the solvent.
                       Tape Casting Process
                        Department of Materials Science and Engineering



                 Creating the Slurry
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.
            Problems Encountered
               Department of Materials Science and Engineering



• Must have viscosity of maple syrup
 Solved by careful moderation of solvent.

• Must be free of lumps
 Solved by mixing carbon with solvent and
 binder with solvent separately, then
 sonicating for 10 minutes.
• Must be cast directly onto electrodes
 Solved by drilling holes into a wooden board.
                 Tape Casting Process
                 Department of Materials Science and Engineering



           Casting the Electrode
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.
                          Future Work
             Department of Materials Science and Engineering




• Carbon nanotubes
• Metal powder (Cr, Al)
• Different binder (Teflon, PVDC)
• Electrochemical Analysis of the
  Samples
• Improve Final Tape Properties
      Acknowledgements
  Department of Materials Science and Engineering




 John Chmiola
Dr. Yury Gogotsi
 Dorilona Rose
DREAM Program
Drexel University
                                            References
                               Department of Materials Science and Engineering



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.

				
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