HORIZON 2020 EUROPEAN UNION FUNDING FOR RESEARCH & INNOVATION
Graphene based electrodes for high performance supercapacitors
Paolo Bondavalli, Head of nanomaterial topicUMR 137 Thales/CNRS Joint team, Physics GroupThales Research and Technology
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materialsConclusion and perspectivesFunding
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materialsConclusion and perspectivesFunding
Research & Technology
The Thales Group
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THALES RESEARCH & TECHNOLOGY
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INDUSTRIALSALCATEL
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Corporate Communications February 2011
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Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materials Conclusion and perspectivesFunding
C=(ε/δ)AE=(1/2)CV²P=V²/(4R)
Helmotz’s model
What’s a supercapacitor?
separator
Two electrodes
Technically is defined Electrical Double Layer Capa citor (EDLC)
Supercapacitor is the name done by NEC in 1971
δ
Battery-like devices
Advantages Very high rates of charge and dischargeHigher life cycle (>500000, rechargeable batteries can attain 10000)Good reversibilityLow toxicity of material usedHigh cycle efficiencyLow internal resistance (Higher output power)Extremely low heating levels
DrawbacksLow amount of energy stored (3-5 Wh/Kg vs 30-40 Wh/ Kg for batteries)It requires sophisticated control and switching equ ipment(from batteries to supercaps)
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materials Conclusion and perspectivesFunding
Some visible supercap applications
.
Aerial lift
Nuremberg Shangai
London
Emergency issues
Emergency issues
Wind Turbine pitch control
Forklift Truck
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materials Conclusion and perspectivesFunding
Activated carbon
Activated Carbon• Large surfaces (3000m²/g)• Low-cost material
Main parameters• Surface (energy)• High breakdown voltage (energy)• Pore size (to exploit surface completely and to promote easy ion diffusion)
The main issue :• Very bad mesoporous distribution!!!2/3 of the pore size are smaller than 2 nm and so are unpercolated)
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materials Conclusion and perspectivesFunding
Electrode material
� CNT/graphene/graphite composite
2. Experimental section
Research & Technology
22
U. Khan, J. N. Coleman et al Carbon (2010)
Can we improve the Power output (P∝∝∝∝ 1/R)?
Why to use Graphite/Graphite/CNTs mixings?
Resistance is reduced by a factor of 4 compared tobare CNTs layers
75% the conductivity is optimized
2. Experimental sectionWhy to use Graphite/Graphite/CNTs mixings?
Pristine graphene/graphite
Graphene/graphite/CNTsmixing
• CNTs prevent restacking (higher surface, higher energy stored)• CNTs/graphite/graphene improve conduction (higher power delivered)• CNTs prevent the disintegration of the composite
reduced charge diffusion
and surface
2. Experimental section
Graphite flakes
OUR APPROACH
CNTs
Separated weighing
Separated dispersion (solvent = NMP )
Dilution to get Csolide = 0,5g/l
25
2. Experimental section
Initial sonication- CNT : 10’ high power- Graphite : 18h low power
Centrifugation 10 minutes x2
OUR APPROACH
Final sonication of the mixture : 18h low power
OUR APPROACH
Deposition method
� Excellent reproducibility
� Versatile, easily scalable for large-area applications
� Extremely uniform deposition with no “coffee-ring” effect
Introduction
27
z
y
x
Noozle
Heating plate3-axes displacement
Dynamic spray-gun deposition method
Process patented
Air-brush deposition
� Gun spraying
� Masking
� Several samples fabricated at the same time
Research & Technology
28
2. Experimental section
Supercapacitor CellFlexible electrodes
Electrode design and cell fabrication
2cm²
Electrode design
Panasonic Graphite bucky paper
Research & Technology
29
2. Experimental sectionSample Morphology (cross section)
Graphite/graphene
Excellent intercalation of graphite/graphene layers
A - Influence of the CNT concentration (Electrodes)
� Energy max. ~4,5Wh/kg for 75wt%CNT
� Power max. ~35 kW/kg for 25wt%CNT (enhancement of 2,5)
3. Results
30Results : Energy and Power as a function of the concentration
25% 75%
Sample characteristics : • weight = 1.8mg• surface = 2cm² (circular design)• thickness ~ 20µm
Last measurements : new option for green suspension s
Advantages• Aqueous based supensions• Very stable suspensions• Low temperature process (120°C)
Mixing of Graphene Oxyde and Oxydised Carbon Nanotu bes in water
GO dispersion CNTox dispersion
Blending of the suspensionsUltrasonication
CNT oxidation
Depot/coating on collectorSpray
Surface expansion Thermal treatment
HNO3H2SO4
CNTs
bundlesSWCNTs
HO
O
HOOC
HO
OH
O
HOOC
COOHCOOH COOH
COOH
COOH
Aqueous dispersion
Nanostructuredmaterials
Mixed dispersion pre-assembly
Hybrid hierarchical architectureHigh electrolyte-accessible area
Aqueous dispersion
Stacking graphene structureLow electrolyte-accessible area
Electrodes preparation
Bought
Oxidised CNTs can be put into water based suspensio ns very easily
Non-oxidised CNTsOxidized CNTs
New packaged prototypes
GO
GO 50% CNT 50%CNT 100%
Previous results
Patent submitted
C (F/g)
mV/s
Strong enhancement of the capacitance For spray gan based samples compared to Bucky paper
Performances for different GO concentrations
E vs Ag/AgC (V)0,50-0,5
I (A
/g)
3
2
1
0
-1
-2
-3
-4
spray 60/40 GO/CNToxspray 70/30 GO/CNToxspray 80/20 GO/CNToxspray 90/10 GO/CNTox
Three-electrodes configuration
Aqueous electrolyte : LiNO 3 3M
Windows of potentiel : 1,6 V
C = 88 F/gC = 109 F/g
C = 106 F/g
C = 117 F/g
C = 112 F/g
spray 100% GO
At 20 mV/s :
Power density
Re(Z)/Ohm5000
-Im
(Z)/
Ohm
450
400
350
300
250
200
150
100
50
0
Re(Z)/Ohm151050
-Im
(Z)/
Oh
m
6
5
4
3
2
1
0
GO/SWCNT 80/20GO/SWCNT 70/30GO 100%G3-IIT/SWCNT
Power density :
100 % GO : 14 kW/kg90/10 : 31 kW/kg80/20 : 29 kW/kg70/30 : 21 kW/kg
To be improved :
- on large surface electrode- by changing the current collector- on large scale- by optimizing the interface electrode material/current collectorand electrode material/electrolyte- By changing electrolyte
Graphene from IIT / SWCNT
0
20
40
60
80
100
120
140
0 100 200 300 400 500 600
Spray graphene exfolié 50/50 et CNT dans NMP
Spray GO pur 170 °C
Spray GO pur 200 °C
Spray GO/SWCNT (75/25) 200 °C
Spray GO/SWCNT (50/50) 200 °C
Spray GO/SWCNT (25/75) 200 °C
Spray SWCNT pur 200 °C
C (
F/g
)
Scan rate (mV/s)
Spray graphene IIT and CNT 50/50 in NMP
Electrochemical performances
Graphene 50%
GO 50%
GO 50% SWCNT 50% and Graphene 50% SWCNT 50% show similar capacitance
GO 75% SWCNT 25%
E (V)1,210,80,60,40,20
0,5
0,4
0,3
0,2
0,1
0
-0,1
-0,2
-0,3
-0,4
-0,5
-0,6
I (A
/g)
initial1000 cycles2000 cycles3000 cycles4000 cycles5000 cycles
-1 0 1 2 3 4 5 6 7
0,0
0,2
0,4
0,6
0,8
1,0
1,2
E (
V)
time (s)
initial after 1000 cycles after 2000 cycles after 3000 cycles after 4000 cycles after 5000 cycles
Galvanostatic charge/discharge experiment
two-electrodes configuration
���� complete system
m = 1,15 mg (x2)
5000 cycles
I= 10mA
Graphene exfoliated by IIT :
- Loss essentially during the 1000 first cycles
-P= 92,3 kW/kg
Electrochemical performances
P=V²/(4RESR2m)
P∝∝∝∝ 1/RESR
0,0 0,5 1,0 1,5 2,0 2,5 3,00
20
40
60
80
100
120
140
160
180
200
220S
peci
fic P
ower
(kW
/Kg)
Weight (mg)
200kW/kg0.25mg (~6Wh/Kg)
60kW/kg
42kW/kg20kW/kg
Graphene exfoliated by IIT :
P= 92,3 kW/kg (It was 16kW/Kg)
Before : (with the mixture Graphene platelets-Graphi te-/CNT)���� High Power density only with very thin layer of act ive material
Now : (with the IIT graphene/CNT)���� High power density, even with such a mass of active material
Factor 5
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materials Conclusions and perspectivesFunding
� New patent on supercaps based electrodes using mixtures of GO andOxidized CNT. Green solution and reduction of process time and of energy(reduced temperature of the process ~120°C, for NMP it was 250°C)
� Improvement of the capacitance using a CNT oxidized/GO composite
� Graphene shows a massive increase in power
� Graphene and Graphene oxide shows similar performances in case ofcapacitance (120F/g) a sample at 90% of GO showed a 100F/g capacitancefor a whole cell (work in progress)
� Very good capacitance with easily implementable fabrication technique
44
Conclusion
Conclusions and perspectives
Perspectives
� To scale up fabrication �
� To transfer the process (Thales Research and Technology is a technology provider)
� To increase the voltage windows by using other kind of electrolytes : organic, ionic liquids…
Supercapacitor electrode based on mixtures of graphite and carbonnanotubes deposited using a new dynamic air-brush deposition technique, PBondavalli, C.Delfaure, P.Legagneux, D.Pribat JECS 160 (4 ) A1-A6, 2013
Non-faradic carbon nanotubes based supercapacitors : state of the art, P.Bondavalli, D.Pribat, C.Delfaure, P.Legagneux, L. Baraton, L.Gorintin, J-P. Schnell, Eur. Phys. J. Appl. Phys. 60,10401, 2012
Outline
Thales group presentationWhat’s a supercapacitors? Visible applications of supercapacitorsWhy to use nanomaterials?Supercapacitors based on Graphene related materialsConclusion and perspectivesFundings
Funding S
Thanks to
In the frame of the Graphene Flagship• Francesco Bonaccorso of IIT for exfoliated Graphene• Graphenea for GO in water
My colleague• Gregory Pognon (Chemistry Lab) Electrochemical characterizationand nanomaterial functionalisation
Thank you for your attention!!!
