Upload
others
View
5
Download
0
Embed Size (px)
Citation preview
Carbon Nanostructured for Energy Storage
Bingqing (B. Q.) Wei
Department of Mechanical EngineeringUniversity of Delaware
Newark, DE 19716, USAEmail: [email protected]
http://www.me.udel.edu/Faculty/wei_group/index.html
NIST Workshop 2011BQWei 1
[1] S.Iijima, Nature, 1991, 354, 56.[2] S.Iijima et al., Nature, 1993, 363, 603.[3] D.S.Bethune et al., Nature, 1993, 363, 605.[4] A.Thess et al., Science, 1996, 273, 483.[5] C.Journet et al., Nature, 1997, 388, 756.[6] H.Zhu et al., Science, 2002, 296, 884.
C60
MWNT [1]SWNT [2,3]
1985
1991
1993
1996
1997
Arc [5]Laser [4]
[7] Z. Wu et al., Science, 2004, 305, 1273.[8] K. Hata et al., Science, 2004, 306, 1362.[9] M. Zhang et al. Science, 2004, 306, 1358. [10] M. Zhang et al., Science, 2005, 309, 1217.
20022004
2004
1-D Strands [6]2-D Film [7] 3-D Arrays [8]
Yarns [9]
2005Macro-sheet[10]
2004
NIST Workshop 2011BQWei 2
Assembly of nanoscale building blocks (CNTs)
into controlled 2-D multifunctional macroscopic
structures for various applications
NIST Workshop 2011BQWei
Properties:
• Low resistivity
Ballistic Electron Conduction
• Small Dimensions
• Mechanical Robustness
• Chemical Stability
• Structural Stability
• High Thermal Conductivity
Low Dissipation
• High Current Densities (~109 A/cm2)
• High Surface Areas
3
Why CNT Films for Supercapacitors?
Films are synthesized by utilizing
a liquid free precursor system in
which ferrocene/sulfur powders
(atomic ratio Fe: S = 10: 1) are
mixed uniformly and evaporated in
a CVD reactor under argon
atmosphere
Synthesis
• Si •Copper• Stainless steel• Aluminum• Nickel mesh• Polymer• …
Zhu and WeiChem. Comm., 2007
Synthesis of Flexible CNT Macro-Films
NIST Workshop 2011BQWei 4
movie1.avi
NIST Workshop 2011BQWei
• Characteristic of SWNT film: demonstrates structural combination of
mesoporous and macroporous materials.
• Compared with nanoporous carbon materials, counterions are
expected to easily and quickly reside at the SWNT electrode/electrolyte
interface without having to enter the pores, leading to an exohedral
supercapacitor with a higher power density feature.
2 4 6 8 10 12 140.00
0.08
0.16
0.24
0.32
Po
re V
olu
me
(c
m3/g
)
Pore Width (Ao)
Surface area of SWNT film: 700 m2/g
Structural Features of SWNT Films
5
SWNT bundles
Flexible, Machinable, Freestanding SWNT films
NIST Workshop 2011BQWei 6
α=148o α=85o α=121o
H2O
H2O
H2O
H2O
C2H5OH
C2H5OH
C2H5OHDWNT-1 DWNT-2 DWNT-3
α=70o
Hydrophilicity Tuning
Hydrophobic
Hydrophilic
Wei, et al.,Adv. Mater., 18, 1695 (2006).
Heat treatment in air at 450 0C for
half hour to remove amorphous
carbon
Treatment in 100% hydrochloric
acid at room temperature for half
hour to remove catalyst particles
Purification
Hydrophilicity
NIST Workshop 2011BQWei 7
Schematic Representation of Electrical
Double Layer Capacitor
Separator
Current collector
(+) (-)
Porous electrode
(SWNT film)
Electrolyte
(TEABF4/PC)
Positive charge
Negative charge
Anions
Cations
Electrical double
layer
Electrolyte: Tetraethylammonium tetrafluoroborate/Polypropylene carbonate
Charge-Discharge cycles: Diffusion and charge accumulation near the electrodes
8NIST Workshop 2011BQWei
Comparison of Li Ion Battery and
Supercapacitor
Rechargeable Li battery
• Involves chemical reactions
• Long duration charge discharge
cycles (several hours)
• High energy density low power
density device
• Low self discharge
• Life time: 1000 - 2000 cycles
• Typical energy density: 10 – 300
Wh/kg
• Typical power density: 100 – 1000
W/kg
Supercapacitor
• No major chemical reactions
involved
• Short duration charge discharge
cycles (few seconds to minutes)
• High power density-low energy
density device
• High self discharge
• Life time: hundreds of thousands
of cycles
• Typical energy density: 0.1 – 5
Wh/kg
• Typical power density: 1000 –
1000,000 W/kg
9NIST Workshop 2011BQWei
Punching Nanotube Electrodes
Purified SWNT films are dispersed
in water and are deposited on a
wire mesh to get a free standing
film
SWNT electrodes are directly
obtained by punching using an arc
punch with required diameter
Flexible, Machinable, Freestanding SWNT films
NIST Workshop 2011BQWei 10
Motivation
NIST Workshop 2011BQWei 11
New Sony Technology %5bwww.keepvid.com%5d.mp4Nokia.wmv
Wavy Silicon StructuresKhang, Jiang, Huang, Rogers, Science, 2006
• Flat Si ribbon becomes buckled due to pre-strained PDMS
Fabricate thin ribbon
Si device elements
Si
Bond elements to prestrained
elastomeric substrate PDMS
PDMS
Peel back PDMS;
flip over
LdLpre
pre
PDMS
mother wafer
NIST Workshop 2011BQWei 12
Buckled CNT-Macro-films on PDMS
4 m
NIST Workshop 2011BQWei
Adv. Mater., 2009.
13
Interface Bonding
• Surface treatment on PDMS substrate
Ultraviolet/ozone (UVO) treatment to
oxide PDMS surface and generate active
OH- group
• Functional group in CNT macro-films
contact condensation reaction
PDMS CNT macro-films
interfacePDMS
CNT macro-film
hole
FIB/SEM image
3 m
NIST Workshop 2011BQWei
4 m
14
NIST Workshop 2011BQWei
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-0.0016
-0.0008
0.0000
0.0008
0.0016
0.0024 Stretchable supercapacitor
Stretchable supercapacitor
subjected to 30% applied strain
Scan rate: 1000 mV/s
Cu
rren
t (A
)
Voltage (V) 0 200 400 600 800 10000
15
30
45
0
15
30
45
Stretchable supercapacitor
Supercapacitor
Sp
ec
ific
cap
ac
ita
nc
e (
F/g
)
0
15
30
45
Stretchable supercapacitor
subjected to 30% applied strain
I = 1 A/g
I = 1 A/g
Cycle number
I = 1 A/g
100 1000 10000
10
8
6
4
2
Stretchable supercapacitor
Stretchable supercapacitor
subjected to 30% applied strain
Supercapacitor
En
ergy d
ensi
ty (
Wh
/Kg)
Power density (W/Kg)
Reversibly Stretchable Supercapacitor
15
NIST Workshop 2011BQWei
Wettability and Ion-size Effect of
Different Aqueous Electrolytes
ACS Nano, 2010
16
Electrochemical Behavior of SWNT Supercapacitors
under Compressive Stress
NIST Workshop 2011BQWei
Pressure (psi) Knee frequency (Hz)
LiOH NaOH KOH LiCl NaCl KCl KNO3
0.37 0.16 0.16 0.16 4 4 13 4
1.12 0.85 0.85 0.85 13 13 34 13
6.58 41 41 41 72 72 72 72
19.74 126 126 126 385 385 385 385
118.44 672 672 672 672 672 672 672
250.04 1172 1172 1172 1172 1172 1172 1172
Knee frequency (experiment data) vs. Pressure
An Excellent High-power Capability under Pressure
17
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-0.0010
-0.0005
0.0000
0.0005
0.0010
25 0C
50 0C
75 0C
100 0C
Cu
rre
nt
(A)
Voltage (V)
Scan rate: 50 mV/s
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5-0.015
-0.010
-0.005
0.000
0.005
0.010
0.015
25 0C
50 0C
75 0C
100 0C
Cu
rre
nt
(A)
Voltage (V)
Scan rate: 1000 mV/s
Capacitance obtained from CV at Different
Temperatures with Different Scan Rates
NIST Workshop 2011BQWei
Masarapu, et al., ACS Nano, 2009
18
0 2500 5000 7500 100000
5
10
15
20
25
30
25 0C
100 0C
Ca
pa
cit
an
ce
(F
/g)
50 A/g
100 A/g
Cycle Number
20 A/g
0
6
12
18
24
30
25 0C
100 0C
0
7
14
21
28
35
25 0C
100 0C
c
0 2 4 6 8 10 12 14-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Over Shoot
Vo
lta
ge
(V
)
Time (sec)
Over Shoot
20 A/g
100 oC
a
0 1 2 3 4 5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Vo
lta
ge
(V
)
Time (sec)
100 oC
100 A/g
b
NIST Workshop 2011BQWei 19
Super-high Power Density
Long Lifetime Supercapacitors at a High Temperature
NIST Workshop 2011BQWei
0 80000 160000 2400000
8
16
240
8
16
24
20 A/g
25 oC
Efficiency: 82%
Ca
pa
cit
an
ce
(F
/g)
Cycle number
20 A/g
100 oC
Efficiency: 84%
20
Masarapu, et al., ACS Nano, 2009
SWNT Supercapacitor
0.1 1 10 100 1000
0.1
1
10
100
1000
DOE
target
SWNT
capacitor
from this
experiment
Batteries
Carbon
capacitors
Metal oxide
capacitors
En
erg
y d
en
sit
y (
Wh
/kg
)
Power density (kW/kg)
Flywheels
Department of Energy
(DOE) Target
Ragone Chart
NIST Workshop 2011BQWei
100 1000 10000
0.01
0.1
1
10
En
erg
y d
en
sit
y (
Wh
/Kg
)
Power density (W/Kg)
25 oC
100 oC
21
The best energy retention capability of SCs
NIST Workshop 2011BQWei
We have studied and understood that there
are different mechanisms over self-
discharge of capacitors, indicating
combination of electrode/electrolyte
governs the self-discharge mechanism. By
selecting the right combination of
electrode/electrolyte, more than 70%
charged energy retained after self-
discharge for 36 hrs
22
Si subtrate
MOSFET
Gate
CMOS via
CMOS wiring
SiO2 Insulation
CMOS to
CNT Via
SWNT film
Polymer electrolyte film
SWNT film
Drain Source
The CNT SCs will be attached to the
top of CMOS chip with
interconnection between them, using
one extra post-CMOS process.
Therefore, it will provide a new low-
cost manufacturing method for
highly functional and compact
systems.
Fully on-chip capacitive devices for SoC design
Besides acting as the energy sources, CNT SCs can also be used to meet the
requirements on large capacitor design for signal processing, sample and hold,
frequency compensation, noise decoupling, tuned resonator, memory design and so on,
enabling fully on-chip capacitive devices.
NIST Workshop 2011BQWei 23
Heterogeneous Integration of CNT
supercapacitors on CMOS process
New Energy Storage and Management Structure
Power
Converter 1
Power
Converter 2
Power
Converter 3
Power
Converter 4
Module 1
Module 2
Module 3
Module 4
Main
Storage SC0
SC1
SC2
SC3
SC4 Point-of-Load
(POL) Sources
Energy
Harvester
Energy Storage and Management System
Power Management Unit
Energy Storage and Sources: a main storage SC0 and four point-of-load (POL) sources, SC1~SC4.
PMU: hardware-based executing platform for power management, mainly composed of power converters, i.e., DC-DC converters. (four modules are shown as an example)
Features:
Multi-energy-source structure: SC0~SC4 are all energy sources for the MSN, which provides the system with
flexibility to assign appropriate voltages to different functional modules. .
Global power management capability: a global energy management strategy can be introduced to deliver energy among energy storage and sources.
NIST Workshop 2011BQWei 24
IEEE TRANSACTIONS ON POWER ELECTRONICS, 2010.
NIST Workshop 2011BQWei
•Si makes it an excellent candidate for electrode materials
in Li-ion batteries. However, volumetric change (400%)
upon insertion and extraction of Li (Li22Si5 alloy), resulting
in pulverization and early capacity fading.
Si: An Excellent Material for Li-ion Batteries
0 10 20 30 400
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
Sp
ec
ific
Ca
pa
cit
y (
mA
h/g
)
Cycle Number
Si anode
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Specific Capacity (mAh/g)
Graphite
Silicon
25
NIST Workshop 2011BQWei 26
Si thin film
CNT film
Current collector
Tandem Structure Formation
Electrode Preparation
High-Vacuum
Electron-Beam
Evaporation
Tandem Structure
Si-SWNT-Cu
Si-Cu
Substrates
Vapor
Si target
Electron Source
NIST Workshop 2011BQWei
ACS Nano, 2010
27
NIST Workshop 2011BQWei
Preliminary Results
Si film thickness easily controlled within 1
nm, with ultimate thickness up to 1-2 µm
achievable
Increased Energy Density
by 3.6 times
Improved Cycle Life
28
Preliminary Results
Si Structure Evolution
LithiationLithiation
SWNT
Si
Cu
Delithiation Delithiation
Si
Cu
Si
Cu
Si
Cu
SWNT
29NIST Workshop 2011BQWei
Conclusions
• Different supercapacitors can be assembled that
demonstrated different functions for promising
applications in electronics:
High Flexibility/stretchability
High operation temperature
Long lifetime
Super-high power density
Mechanical robust under compression
High energy retention with small leakage
NIST Workshop 2011BQWei 30
CNT Power Sources for: