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

Department of Materials Science and Engineering Overview 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

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. 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

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., 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., 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.,  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 Invent a process that decreases the resistance between the current collector and the electrode Decrease the resistance inside the carbon electrode MWNT [1] SWNT [2] fb-MWNT [3] a-C [3] C cloth [4] Capacitance (F/g) Previous work found that Ti 2 AlC 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 °C during mixing. Creating the Slurry

Department of Materials Science and Engineering 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., Singer, Clifford. “Energy Usage.” 4 Sept Thermoanalytics. (2001). Battery Types and Characteristics