1. Inkjet-Printed Graphene for
Flexible Micro-Supercapacitors
IEEE NANO Conference
August 15-18, 2011, Portland, Oregon
Woo Lee
George Meade Bond Professor
Stevens Institute of Technology
Hoboken, New Jersey
Linh T. Le and De Kong, Stevens
Dr. Matthew Ervin, U.S. Army-ARL
Dr. Brian Fuchs and J. Zunino, U.S. Army-ARDEC

2. Graphene:
A New 2D Nanomaterial for 3D Assembly
• Novel Properties www.jameshedberg.com
– Electrically conductive
– Optically transparent
– Mechanically strong & conformal
– High surface area
– Chemically & electrochemically inert
• Diverse Production Methods
– $50/kg anticipated in 3 years for
graphite-derived
• Inkjet-Printed Graphene 3D Assembly with
Micropatterns Inkjet-Printed
– Electrodes for cheap, flexible energy 2D Graphene Nanosheets
storage & generation devices

3. Conventional Supercapacitor
Simon et al.,
Separator Nature Materials,
“−” Ions “+” Ions 2008
Current Current
Collector Collector
Activated Activated
Carbon Carbon
Electrode Electrode
Concept Flexible
Micro-Supercapacitor Device Attributes
 Integration with flexible electronics
Silver Current
 Higher specific power (~100x
Collectors
batteries)
Hermetic
Seal
 Rapid charge/discharge times
 Millions of charge/discharge cycles
Kapton Graphene Electrolyte  Stable at extreme temperatures
Electrodes

4. Graphene: Ideal Electrode Material
Activated Carbon Graphene
Carbon Nanotubes
Sheet a Yoshida et al, J. Power
Sources, 1996
Resistance 100-500a 10-100b 1000c b Wu et al, Science, 2004
(Ω/ ) c Reina et al, Nano Letters, 2008
*Based on 74 µF/cm2 with KOH
Surface Area 500 1320 2630
(m2/g) (Actual) (Theoretical) (Theoretical)
Capacitance* 120 977 1954
(F/g) (Actual) (Theoretical) (Theoretical)
Can we control the 3D assembly
of conformal graphene
nanosheets during printing and
More
Corrugation? therefore their morphology for
high surface area, ion transport,
and electrical conductivity?

5. Inkjet-Printed Graphene Micropatterns
Vertical Alignment of
16 Piezoelectric Nozzles
20 Droplets
www.dimatix.com
5 ppm Carbon Nanotubes
10 pL Droplet
in Water
25 mm
Process Attributes
• 50 mm resolution
• Net-shape with minimum
nanomaterial use, handling
& waste generation
• Scale-up & integration
readiness with commercial
printers
Le et al., Electrochemistry Communications, 13, 355 (2011)

6. Graphene Oxide in Water as Scalable Ink
Hydrophilic
Graphene Oxide Stable
Dreyer el al., Chem. Soc. Rev.,
Suspension (0.5%)
2010, 39, 228-240 for Months
w/o Surfactant
High-Throughput Droplet Generation
Reduction to Graphene
• Thermal in hours
• Photothermal in minutes

7. Significant Size & Shape Variations
in Graphene Oxide Ink
Other Characteristics
– z potential: −20 mV
– Viscosity: 1.06 mPa.s
– Surface tension: 68 mN/m
1 mm

8. 1 to 5 Printed Graphene Layers
Glass Kapton
Slide Ag
1 2 3 4 4-Point
Probes
Droplet Spacing Effect (5 Layers)
100 CVD-grown Graphene*
Droplet Sheet Trans-
Spacing Resistance parency
Transparency (%)
90
(mm) (M) (%)
20 0.3 78 80 Inkjet-Printed
30 3.1 85
Graphene*
70
40 5.5 93
60
Inferior sheet resistance of 50 Graphene reduced
photothermally reduced From Graphene Oxide
40 1 2 3 4 5 6 7 8 9 10
graphene oxide (1 M) 10 10 10 10 10 10 10 10 10 10
to chemically reduced Sheet Resistance (/squr)
graphene oxide (1 k)
*Bonaccorso, Nature Photonics (2010)

9. 100 Printed Layers: Surface
20 mm
1 mm

10. 100 Printed Layers: Cross-Section
1 mm

11. Highly Porous Structure Develops
during Printing 100 Layers
0.02
• Method
– N2 isotherm adsorption
dV(w) [cm3/Å/g]
0.015
– BET surface area
0.01
– BJH model for pore size
0.005 distribution analysis
0
0 100 200 300 400
• Bimodal distribution
-0.005 – 1.5-2.2 nm micropores
pore size [Å]
– 11-36 nm mesopores
Total Micropores Mesopores
• Relatively narrow pore
Surface 282 140 142
Area (m2/g) size ranges
Volume 1.36 0.0846 1.27
(cm3/g)

12. Electrochemical Properties Capacitive Cyclic
Teflon Blocks
Voltammetric Behavior
Celgard
Separator
Titanium Foil
Current Collector
Inkjet-Printed
Graphene
1M H2SO4 Electrolyte
Linear Galvanostatic
Charge/Discharge
97% Capacitance
Retention

13. Incompatible
Performance with Inkjet- • Microwave for
Printed Flexible corrugated GO
Graphene • KOH activation to
Printed Electronics
(Powder create 1-10 nm pores
Graphene
Methods) Aligned MWCNT [4] • 3100 m2/g [5]
Capacitance ~100[1]
(F/g) 132
~117[2]
Energy
Density 4.1[2] 6.74
(Wh/kg)
Specific Power (kW/kg)
Power
Density 10[3] 2.19 10
(kW/kg) 1
Important Structural Features 0.1
• Graphene alignment to electrical 0.01
current flow 0.1 1 10 100
• Interconnected 1-10 nm porosity Specific Energy (Wh/kg)
for higher ion accessibility and
Comparison to “Best” Electrodes
conduction
[1] Stoller, 2008; [2] Vivekchand, 2008 ;
[3] Wang, 2009 ; [4] Honda, Y. , 2007; [5] Zhang., 2011

14. Effect of Droplet Spacing
d1
d2
d1 & d2= 15 mm
d1 & d2= 25 mm
2 mm
1 mm
d1 & d2= 5 mm
More
Corrugation?
2 mm

15. Overall Device Level Challenges
Graphene Electrode Hermetic Packaging to Keep
3D Assembly Electrolyte from Leaking & Drying
– Heat-sealable pouch
– Adhesive bonding via soft-
lithography
Chemical & Electrochemical Silver Current
Collectors
Compatibility
– Electrolyte selection & testing Hermetic
Seal
– Ag current collector as
commercially available inkjet-
Graphene Electrolyte
printed material Kapton
Electrodes
– Packaging materials
Printing Process
Ag printed & cured @130oC
– Initial surface effects
– Ink optimization with controlled
size and shape distributions
– High speed operation

16. Conclusions
• Inkjet-printed 3D graphene
De Kong
assembly demonstrated as
high surface area
supercapacitor electrodes
with promising
electrochemical properties.
• Inkjet-printing based on: (1) Linh
hydrophilic graphene oxide Le
dispersed in water as a stable
ink and (2) post thermal or
photothermal reduction.
Acknowledgements
• Flexible micro-supercapacitor
• “Integrated Flexible Energetics
device being developed with and Electronics,” U.S. Army -
printed graphene as ARDEC
micropatternable electrodes. • Tim Luong, Fujifilm-Dimatix

17. Backup

18. Hon et al., Commercial
CIRP Annals, 2008
Printers
www.dimatix.com
Cartridge
Sono-Plot
16 Microfabricated
Piezoelectric Nozzles
1 or 10 pL Droplets

19. Flexible HP-ASU
Electronics
• Roll-to-Roll
Printing
Inkjet-Printed
• Evaporative Silver Conductor
Assembly of
Nanomaterials
under
Microfluidic 200 nm
Control
Silicon Flexible
Electronics Electronics
Transistors Billions Thousands Reference:
FlexTech
Feature Size 10-2 mm 10 mm Alliance (2009)
Cost of Fab $2-3B/Fab $10-200M/Fab

20. Woo Lee’s Group
in vitro Transformative
3D Bone Tissue Biomedical & Energy
Devices
200 mm
Microfluidic
Tools
Nanomaterial Nanoscale
Assembly Materials
Partnerships for
Translation and Impact
1 mm