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Probing, Charging and Discharging of Single Probing, Charging and Discharging of Single SSNanoporesNanopores in a in a SupercapacitorSupercapacitor
Pingshan WangElectrical and Computer Engineering Department Clemson UniversityDepartment, Clemson University
Jim RuiMechanical Engineering DepartmentClemson Universityy
ContentsContents
Background– Probing the fundamental processes in electrochemicalProbing the fundamental processes in electrochemical
capacitors (EC)– On-chip dielectric spectroscopy with microfluidic and nanofluidic
channelschannels
Dielectric spectroscopy with planar micro/nanofluidic channels for EC process probing– Nanofluidic channel fabrication– Dielectric spectroscopy methods– Molecular dynamics simulationy
1/21/2009 Capacitor Consortium Planning Meeting 2
Background: Wetting and ion transport in ECsBackground: Wetting and ion transport in ECs
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+ + + + + + + + + + + + + +
• Wetting characteristics in nanoporesWetting characteristics in nanopores• Ion transport: electrolytes for performance
Nanoscale systems
* Modified from Fig. 16 on p. 55 of Basic Research Needs for Electrical Energy Storage
yPores: 0.5–3 nm in size)
1/21/2009 Capacitor Consortium Planning Meeting 3
Background: Charging and discharging at atomic levelBackground: Charging and discharging at atomic level
• Correlation between pore size, ion size, surface area, surface chemistry and EC performance
• Solvation dynamics, molecular interactions at the interfaces
• Electrolyte/electrode interface during charging/discharging at molecular andcharging/discharging at molecular and atomic levels
• Calibrated and valibrated predictive models for capacitive energy systems: nm to mm
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and picosecond to microsecond.
+ + + + + + + + + + + + + + + + + + + + + ++
1/21/2009 Capacitor Consortium Planning Meeting 4
* Modified from Fig. 16 on p. 49 of Basic Research Needs for Electrical Energy Storage
Background: onBackground: on--chip dielectric spectroscopy with chip dielectric spectroscopy with micro/micro/nanofluidicnanofluidic channelschannels
Dielectric spectroscopy (Impedance spectroscopy)
micro/micro/nanofluidicnanofluidic channelschannels
Dielectric spectroscopy is complementary to• Nuclear magnetic resonance (NMR)• Neutron scatteringNetwork
analyzer • Mechanical spectroscopy• Debye relaxation
analyzer
μmnm
W( ) where is the permittivity at the high frequency
Sample holder
nm e e s t e pe tt ty at t e g eque cylimit, , is the static, low frequency permittivity, and τ is the characteristic relaxation time of the medium.
Nanofluidic channel
1/21/2009 Capacitor Consortium Planning Meeting5
Background: micro/Background: micro/nanonano fluidic channelsfluidic channels
Glass wafer
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
G
10 µmG
S
Silicon
MUT
Si
G’ L R C’
MUT
Si
C G
Water flow video
1/21/2009 6Capacitor Consortium Planning Meeting
1/21/2009 7Capacitor Consortium Planning Meeting
Background: Background: microfluidicmicrofluidic channels and resultschannels and results
60t)
Microfluidic channels Measurement setup
45
50
55
60
(Imag
inar
y Pa
rt
• ~ 50 kV/cm electric field• Slightly different from ordinarily
40
45
15 20 25 30 35 40 45 50 55 60 65
Perm
ittiv
ity (
Permittivity (Real Part)
• Slightly different from ordinarily accepted 80
Water dielectric permittivity
1/21/2009 8Capacitor Consortium Planning Meeting
Proposal: probing fundamental process in ECs with 1Proposal: probing fundamental process in ECs with 1--1000 nm planar micro/nanofluidic channels1000 nm planar micro/nanofluidic channels1000 nm planar micro/nanofluidic channels 1000 nm planar micro/nanofluidic channels
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1 nm
Wetting
+ + + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + +
-
+
G’ L
C
R C’
G +C G
On-chip dielectric spectroscopy
Charging and discharging
Different electrolytes
1/21/2009 Capacitor Consortium Planning Meeting 9
p p py y(bulk vs. confined)
Microfluidic channels: fine.Microfluidic channels: fine.Nanofluidic channels: is it possible?Nanofluidic channels: is it possible?Nanofluidic channels: is it possible?Nanofluidic channels: is it possible?
5 µm~ 4 nm
Surface roughness
~ 60 µm
Surface roughness
~ 60 µm
~14 nmAFM 3D_AFMSilicon transmission lines
1/21/2009 Capacitor Consortium Planning Meeting 10
Silicon transmission lines
Proposal: probing fundamental process in ECs with 1Proposal: probing fundamental process in ECs with 1--1000 nm planar micro/nanofluidic channels1000 nm planar micro/nanofluidic channels1000 nm planar micro/nanofluidic channels 1000 nm planar micro/nanofluidic channels
+ + + + + + + + + + + + + +
+ + + + + + + + + + + + + +
1 nm
Wetting
+ + + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + +
-
G’ L
C
R C’
G +C G
Charging and discharging1 M quaternary ammonium bis(oxalato) borates (QABOBs)/propylene carbonate solutions
1/21/2009 Capacitor Consortium Planning Meeting 11
q y ( ) ( ) p py1 M Et4NBF4/propylene carbonate
Long term goals and 1Long term goals and 1--year deliverablesyear deliverables
Long term goals– Understand wetting charging and discharging processes of ECsUnderstand wetting, charging and discharging processes of ECs
at the atomic level– Establish corresponding models
Understand the interactions charged electrodes and electrolytes– Understand the interactions charged electrodes and electrolytes– Help identify the properties of perfect electrolytes for ECs
First year deliverables– Microfluidic channels and dielectric characterization of two
electrolytes: 1 M quaternary ammonium bis(oxalato) borates (QABOBs)/ propylene carbonate solutions, and 1M Et4NBF4/propylene carbonate.
– Planar nanofluidic channels with ~ 1 nm (silicon and SiO2 surface)
– Initial results on wetting and charging and discharging models
1/21/2009 Capacitor Consortium Planning Meeting 12