Materials in the Flatland: processing,
characterization and beyond.
Towards high efficiency
energy storage
Prof. Valeria Nicolosi
[email protected]
CRANN
Low-dimensional Nanomaterials:
wonder materials with some critical issues
Applications hampered by difficult processing
 How to process these materials?
 Can we correlate and tune structures to properties?
 Is scaling-up feasible? Can we enter these material into
the applied world?
Graphene – A tiny BIG thing:
how can it be made?
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A different approach:
Liquid-phase Exfoliation
In 2008 we found tens of solvents able to
disperse and exfoliate graphite
Gmix  H Mix  TS Mix  0
 Need to reduce HMix
-ve
H Mix
2
 g   sol 2V f

VMix
T flake
g
i
 i  ESur
Need to match total surface energies of
G
Sol
graphite and solvent: ESur
 ESur
Y. Hernandez, V. Nicolosi et al., Nature Nanotechnology, 3, 9, 563-578 (2008)
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ΔHmix is minimised when the total surface energy
of 2D crystal and solvent are matched.
Y. Hernandez, V. Nicolosi et al., Nature Nanotechnology, 3, 9, 563-578 (2008)
Easy, cheap and scalable method…
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NMP
1 mm
500nm
500 nm
-Y. Hernandez et al.,
Nature Nanotechnology, 3, 9, 563-578 (2008)
- Nature Nanotechnology, News and Views, 3, 9, 528-529 (2008)
- Nature Nanotechnology Editorial, , 3, 9, 517 (2008)
Easy to control the final conc.
and the single flake yield
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Aberration-Corrected HRTEM reveals a defect-free structure
2.4
Å1.42 Å
30000000
Intensity (a.u.)
Intensity (a.u.)
300
20000000
200
10000000
100
0
0,0
0,2
0,4
0,10
0,15
0,20
0
0,6
0,8
1,0
0,25
0,30 (nm)
0,35
Distance
Distance (nm)
1,2
0,40
1,4
0,45
0,50
A step further: graphite is not the
only layered material in nature...
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ThisBoron
is justNitride
a flavour:
(BN)
There are hundreds of
different types of layered
TMCs and TMOs:
Tungsten Disulphide
- Metals
(WS2)
- Semiconducting
Molybdenum Disulphide
- Insulators
(MoS2)
How to handle these materials?
Lets learn from graphene dispersions...
MoS2 powder
WS2 powder
hBN powder
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Solvent testing
BN
WS2
MoS2
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J.N. Coleman, et al.,
Science, 331, 6017, 568-571
(2011)
V. Nicolosi, J.N. Coleman
Patent 1101482.6
Exfoliation confirmed by
conventional TEM
Patent application: 1101482.6
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J.N. Coleman, V. Nicolosi, Science, 331, 6017, 568-571 (2011)
Exfoliating the Inorganics:
Aberration-corrected TEM
hB
hBN
hBN
N
MoS
MoS
22
2
WS
W
WS
2 2
S2
2 nm
2 nm
2 nm
hBN
MoS2
WS2
Patent application: 1101482.6
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J.N. Coleman et al., Science, 331, 6017, 568-571 (2011)
Aberration-corrected STEM:
“Z-Contrast”
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Nion UltraSTEM – 60kV
ORNL
 Each hexagonal ring (green circle): three
brighter N atoms and three darker B atoms
but there were some deviations....
O. Krivanek et al., Nature, 464, 7288, 571-574 (2010)
Aberration-corrected STEM:
“Z-Contrast”
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C = yellow
B = red
N = green
O = blue
Quantitative
atomic
“gentle” imaging
From 4.5 to 0.15
eV asresolution
the
now possible…
C contentisisfinally
increased
O. Krivanek
etL.
al.,Song,
Nature,
464,Materials,
7288, 571-574
(2010)(2010).
L. Ci,
Nature
9, 430-435
Some applications:
Free standing films
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Films of MoS2, WS2 and BN (and graphene hybrids) - thickness ranging from ~50
nm to >50 μm.
BN
MoS
2
Graphene
Graphene / Graphene /
BN
MoS2
Patent application: 1101482.6
WS2
Graphene /
WS2
J.N. Coleman et al., Science, 331, 6017, 568-571 (2011)
Some applications:
Free standing films - tensile testing
Young’s modulus
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With the exception of the BN,
all films have:
Ultimate Tensile Strength
Y close to 1 GPa
UTS close to 5 MPa
Strain at break
εb close to 0.5%
Values typical for
weak thermoplastics…
J.N. Coleman et al, Science, 331, 6017, 568-571 (2011)
Some applications:
Composites
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Composites: thermoplastic polyurethane filled with exfoliated
MoS2, WS2 and BN (5wt% and 20wt%)
J.N. Coleman et al., Science, 331, 6017, 568-571 (2011)
Some applications:
Composites- Tensile testing
Young’s
Young’smodulus
modulus
Ultimate
Tensile
strength
Ultimate
Tensile
strength
Strain at break
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significant
in the
To date,increases
it had been
Young’s
modulus
impossible
to
(samecomposites
order as the
prepare
with
best
nanotube
reinforced
exfoliated
TMCs
without
elastomers)
lithium
intercalation
increases in tensile strength
Even then the choice of
(more for the 5% filler)
polymers was very small due
to the extremely limited
solvent choice
some decreases in ductility
(for
CNTs
ductility
usually
Now
we have
a broad
falls
catastrophically)
solvent
choice:
broader application range!
Some applications:
Supercapacitors
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Supercapacitors for Energy Storage
E&P
•high surface area
• porosity
• high conductivity
• electrochemical stability at the
Electrochemical double layer Capacitors
applied Voltages
(Supercapacitors)
• Resistant to temperature
x-C +)
Resistant
to- mechanical
[M]•surf
+ xC+ + xe
([M]strain
x surf
generated by charging/discharging
MOn +
xC+
+
xe-
C MOn
2D materials are ideal!x
P-
• small thickness
W-
Q
1
2
W =
CV ; C =
2
V
P =
V2
4RS
ε0εrA
=
d
Supercaps:
Spraying electrodes
X. Zhao et al,
Nanotechnology, 20, 065605 (2009).
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30 sec
1 min
4 min
8 min
15 min
15 min
B. Sanchez et al, Carbon, accepted
Graphene-based electrodes
Cyclic voltammetry
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• 1M H2SO4 - 1V voltage window
•Range of scan rates from 10 to 10,000 mV/s
•• 500-10,000
10-500 mV/smV/s
• same behaviour up to
mV/s scan rate
•10,000
quasi-rectangular
shape
• significant resistive
only
at at
•behaviour
redox-type
peaks
20,000 mV/sec
~0.4V
B. Sanchez et al, Carbon, accepted
Gravimetric Capacitance Vs Scan Rate
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• C = 542.7 mF/cm2 @ 10,000 mV/s
• 43 % drop @ 10,000 mV/s. (High-performance RuO2-based supercaps (Airbus
380) : 47% drop at 10,000 mV/s)
B. Sanchez et al, Carbon, accepted
Galvanostatic charge/discharge
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Discharge curves @10th cycle
- Current densities of 0.5, 1, 2, 4, 8 A/g:
graphene
• Discharge
• at
CNTs
times: 10s of seconds for graphene - several
minutes for carboxylated SWNTs
least one order of magnitude shorter
than what’s out in the literature for graphene!
Ragone plot
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• voltage scan rates from
10 to 20,000 mV/s
*
*
Max Energy density of
75.4 nWh/cm2 at Power
density of 36.1 nWh/cm2
* Literature data for
ultra-thin graphene
J. J. Yoo et al., Nano Letters, 11,
1423–1427 (2011).
B. Sanchez et al, Carbon, accepted
Cyclability
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cyclic voltammetry for 5,000 cycles at 10,000 mV/s
100 % capacitance retention!
Supercapacitors for Energy Storage
TMCs/TMOs
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• Bulk Birnessite (MnO2) is already very used in
Supercaps technologies
• High dielectric constant - redox activity
(speudo-capacitance)
CONS:
• Not very conductive
• Not very good
cyclability
Bulk Birnessite
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1 μm
-2 -1
Capacitance/
Specific
Acm
g (F/g)Fg
Capacitance
-1
2Mn7  3Mn2  5Mn4
1.2
240
120 0.68 V: cation deintercalation
upon oxidation
0.8
210
100
0.4
180
80
150
0.0
60
120
-0.4
90
40
-0.8
60
V: cation insertion
20 Scan0.5
-1.2
Rate
1000 mV/s
30
upon reduction
0
0-0.2
0.43000
0.64000
0.85000
1.0
00 0.01000
2000.22000
400
600
800
1000
E/V
vs
Ag/AgCl
Scan
Rate
(mV/s)
Cycle
number
Exfoliated Birnessite
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1 μm
0. 2
µm
Hybrids:
Birnessite//Graphene
Capacitance (F/g)
120
100
80
60
40
20
0
33% in weight birnessite/graphene
0
1000 2000 3000 4000 5000
Scan Rate (mV/s)
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Cyclability
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Capacitance Retention (%)
cyclic voltammetry for 3,000 cycles at 5,000 mV/s
110
100
90
80
70
60
33% in weight birnessite/graphene
0
1000
2000
Cycle Number
100 % capacitance retention!
3000
Conclusions
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 Cheap, easy, non-destructive, scalable method for
producing a range of 2D nanostructures
 Aberration-corrected STEM is a UNIQUE way to
investigate these structures at low voltage
 New high-potential applications - Energy Storage:
- combination of electric double layer and pseudo-capacitive
behaviour maintained at scan rates as high as 10,000 mV/s
- Max capacitance of 542.7 mF/cm2
- Capacitive loss of only 43% at 10,000 mV/s
- 100 % capacitance retention up to 5000 cycles
- 100 % capacitance retention at 10,000 mV/s
Acknowledgements
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Beatriz Mendoza
Henrik Pettersson
Mustafa Lotya
Arlene O’Neill
Ronan Smith
Prof. J. N. Coleman
Eleanor Grieveson
Koenraad Theuwissen
Aleksey Shmeliov
Prof. Patrick Grant
Prof. Peter Nellist
Dr. Ondrej Krivanek
Dr. Matt Murfitt
Dr. Niklas Dellby
Prof. Stephen Pennycook
Dr. Matthew Chisholm
: Dr. Timothy Pennycook