carbon nanostructured for energy storage bingqing (b. q.) wei• compared with nanoporous carbon...

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


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


movie1.avi


• 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


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


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


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


Motivation


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


Buckled CNT-Macro-films on PDMS

4 m


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


4 m

14


-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


Supercapacitor

Sp

ec

ific

cap

ac

ita

nc

e (

F/g

)

0

15

30

45



I = 1 A/g

I = 1 A/g

Cycle number

I = 1 A/g

100 1000 10000

10

8

6

4

2




Supercapacitor

En

ergy d

ensi

ty (

Wh

/Kg)

Power density (W/Kg)

Reversibly Stretchable Supercapacitor

15


Wettability and Ion-size Effect of

Different Aqueous Electrolytes

ACS Nano, 2010

16

Electrochemical Behavior of SWNT Supercapacitors

under Compressive Stress


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


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


Super-high Power Density

Long Lifetime Supercapacitors at a High Temperature


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


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


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.


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.


IEEE TRANSACTIONS ON POWER ELECTRONICS, 2010.


•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


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


ACS Nano, 2010

27


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


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


CNT Power Sources for:

carbon nanostructured for energy storage bingqing (b. q.) wei• compared with nanoporous carbon...

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