1. Nick Szamreta Summer of Learning Symposium October 4th, 2013
Measuring the Intrinsic Capacitance of Graphene/Ionic Liquid Interfaces for High Energy Density Supercapacitors
Nick Szamreta
Summer of Learning Symposium
October 4th, 2013

2. Logistical Overview 8 week internship funded by PEI
Facilities at Ceramic Materials Lab (Prof. Ilhan A. Aksay) in Princeton
Collect data on intrinsic capacitance useful for the design of supercapacitors

3. E ~ CV2 Supercapacitors High Power Density Low Energy Density
Can charge and discharge quickly
Low Energy Density
Depends on electrode material (Functionalized Graphene Sheets)
Depends on operating voltage (Ionic Liquids)
E ~ CV2

4. Ionic Liquids Cation (Abbrev.) Anion (Abbrev.)
Bmim+
Tf2n-
Cation (Abbrev.)
Anion (Abbrev.)
1-ethyl-3-methylimidazolium (emim)
bis(trifluoromethylsulfonyl)imide
(tf2n)
1-ethyl-3-methylimidazolium
(emim)
Tetrafluoroborate (bf4)
1-butyl-3-methylimidazolium
(bmim)
1-butyl-4-methylpiperidinium (pip14)
Emim+
Bf4-
Pipip14+

5. Reasons for Studying Ionic Liquids
Large electrochemical windows
Thermal stability
Low vapor pressure
How do these different properties affect capacitance?
Electrolyte
Electrochemical Window (V)
Emimtf2n
4.3
Bmimtf2n
4.8
Emimbf4
4.2
Pip14tf2n
5.0
Aqueous Electrolytes
1-2
Organic Electrolytes
3-5
Barrosse-Antle et al. (2010), Voltammetry in RTIL. Chem. Asian Journal.
E ~ CV2

6. Intrinsic Capacitance Measurements
Three electrode system
Impedance Spectroscopy
Measures the response to an AC signal
Allows us to probe the interface and its electrochemical properties
Intrinsic data for specific combinations of materials is valuable for supercapacitor design
Measurements are much more controlled than a device

7. Sample data
Allows us to compare different materials and electrolytes

8. Conclusions and Continued Work
Ionic Liquids are promising electrolytes for supercapacitors in conjunction with FGS
Testing other ionic liquids
Diluting ionic liquids to increase power density
Building and testing devices

9. Ackknowledgements
Dr. Ilhan A. Aksay
DJ Bozym
Dr. Michael Pope
PEI