Innovative inexpensive supercapacitors

1
Innovative inexpensive supercapacitors
Ranjini Weerasooriyaa, John Chmiolab, Yury
Gogotsib
b Department of Materials Science and
Engineering University of Pennsylvania,
Philadelphia, PA 19104
a J.R. Masterman High School Philadelphia, PA
19130
Intro Supercapacitors
Objectives
Results
Discussion
3
1
Supercapacitors

• Decrease the cost of supercapacitor by using
  least expensive materials
• Simplify processing to level that non-specialist
  can produce supercapacitors
• Compare our method to commercial supercapacitors

• The capacitance of commercial capacitors is
  independent of the current used -
• Published values did not match calculated values
• The paint method showed that the capacitance is
  independent of the current
• The prototype showed some inconsistency because
  of the corrosion of the electrodes
• Only slightly lower capacitance of method 2
  compared to method 1, but simplicity of
  construction makes method 2 more desirable than
  method 1

15 cm X 15 cm electrodes (Method 1) Average
thickness 656µm
Testing of Method 1 capacitor
Materials Methods
4

• Materials
• Aquarium grade activated carbon ( 0.10/kg)
• Salt water (1M NaCl ) as electrolyte
• Stainless steel grid
• Polytetrafluoroethylene (PTFE)
• Cooper Bussman 50F 2.5V commercial supercapacitor

15cm X 7.5 cm electrodes (Method 2) Average
thickness 583µm
Chmiola, J. Gogotsi, Y., Supercapacitors as
advanced energy storage devices. Nanotechnology
Law and Business 4 (2007).
Conclusions
2
Intro Capacitance importance

• Similar capacitance was observed between
  commercial capacitors and prototypes.
• On a commercial scale method 2 is easier to work
  than method 1
• Prepared prototype capacitors that perform
  equally as well as commercial capacitors.
• The innovative method (method 2) was almost as
  good as the coating method (method 1) in
  developing capacitors.
• Succeeded in producing an inexpensive capacitor
  that can be easily fabricated
• Moving from steel to aluminum alloy improved the
  performance of the capacitors

Commercial capacitor used for comparisons

• Methods
• Current collector preparation
• Current collectors cut to required size (15cm
  x15cm, 15cm x 7.5cm , 6cm x 6cm)
• Degreased in ethanol
• Etched in 1M HCl _at_ 80 degrees for 20 minutes to
  remove surface oxides
• Electrode preparation
• Method 1
• 1. Mix 5wt PTFE with 95wt carbon in ethanol
• 2. Heat and stir until ethanol evaporated and
  PTFE evenly distributed in carbon
• 3. Work electrode until pliable
• 4. Cut electrode to size
• Method 2
• Paint was prepared by concentrating 5.5 g of
  Carbon with 0.55 g of PVDF and 50mL of DMF.
• 1. Heat , stir and decant the solution until it
  is thick in consistency
• 2. Paint the cut electrodes
• 3. Dry in oven.

• Capacitance was calculated from the slope of the
  discharge curve, V vs. t, at constant current
• Capacitance values calculated at currents ranging
  from 10 mA to 2 A

Service, R. F., New 'supercapacitor' promises to
pack more electrical punch. Science 313, 902-905
(2006).
Supercapacitors have gt10x higher power density
than batteries
Applications
Acknowledgements
Capacitance calculated by
Charge _at_ 0.75A

• Used as power back-up in products such as mobile
  phones, laptops, radio tuners, digital cameras,
  televisions, and computers
• Also used for energy storage for solar panels,
  motor starters, photo copiers, to larger
  industrial drive systems.
• Are of particular interest in automotive
  applications for hybrid vehicles and as
  supplementary for battery electric vehicles.
• If the cost of supercapacitors can be decreased,
  more applications may become available

I sincerely wish to thank Dr. Mun Choi and Dr.
Yury Gogotsi for their commitment to science
education and willingness to help teachers gain
research experience in the field of Engineering
and Nanotechnology. I also appreciate the efforts
of Mr. John Chmiola , without his help , support
and advice none of this would be possible .The
RETAIN program is funded by the National Science
Foundation. ( NSF award 0601845 , Dr. Mary
Poats-Manager).
Resistance calculated by
Discharge _at_ 7.5A

• Capacitance was normalized by electrode area in
  order to directly compare Method 1 and Method 2