High Capacitance Carbons for Electrochemical Double Layer Capacitors

Patricia H. Smith, Ph.D.Naval Surface Warfare Center- Carderock

(301) 227-4168Patricia.H.Smith1@navy.mil

Goal: High Power, High Energy Density Energy Storage Device for Load Leveling

GOAL

Discharge Time: 10 to 100s sec.Cycle Life: 1,000,000 cycles

ED: 15-25 Wh/kg (70-130 J/cc)PD: 1000-2000 W/kg

G.G. Amatucci, F. Badway, A. Du Pasquier , and T. Zheng, J. Electrochem. Soc., 148 A930 (2001)

EDL Capacitor Li Ion Battery

Asymmetric Hybrid DL Capacitor

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 20 40 60 80 100Vo

ltage

(V)

Depth of Discharge (%)

Li Ion

Asymmetric

EDL

C C LixC6

Li1-xMOY

=

C

Li1-xMOY

E = ½ CV2

Approach: Non-Aqueous, Asymmetric Hybrid DL Capacitor

Low voltage (1.5V vs. Li Ref.)Long cycle life (0% expansion/contraction of crystal lattice) Good rate capability (high surface area nanostructuredmaterial)Undergoes faradaic reaction (battery intercalation process)Good capacity (150 mAh/g)

Negative electrode: Li4Ti5O12

Li4Ti5O12 + 3Li+ + 3e- Li7Ti5O12

Lithium Titanate/Carbon

Courtesy of Altairnano

Collaboration with Glenn Amatucci, Rutgers University

High Voltage (3V vs. Li Ref)Undergoes non-faradaic reaction. (Energy stored electrostatically.)Excellent rate capability and long cycle life.Low capacity (10-30 mAh/g)

Lithium Titanate/Carbon

Positive and negative electrodes not balanced.Energy density limited by carbon.

Positive electrode: Activated Carbon

μM

Investigation

Identify carbons that display high capacitance with lithium electrolytes.

Investigate:Commercially available materialsExperimental materials (SBIRs, Universities)

Minimum voltage decayGood high temperature stability

Non-Aqueous, Asymmetric EDL Capacitor Employing Li Electrolytes

Negative: Lithium TitanatePositive: Activated Carbon

• G.G. Amatucci, F. Badway, A. Du Pasquier , and T. Zheng, J. Electrochem. Soc., 148 A930 (2001).

Negative: Activated Carbon/Pitch compositePositive: Activated Carbon

• A. Yoshino, T. Tsubata, M. Shimoyamads, H. Satake, Y. Okano, S. Mori, and S. Yata, J. Electrochem. Soc., 151 A2180 (2004).

Negative: Lithium Ion (graphitic carbon)Positive: Activated Carbon

• O.Hatozaki, Proceedings from Advanced Capacitors World Summit 2006, San Diego.

Lithium Ion Capacitor

Evaluation of Carbons

Commercial & Experimental Carbons

2” x 3” Pouch Cell

Binding Energy (eV)160162164166168170

Inte

nsity

(cou

nts/

seco

nd)

600

800

1000

1200

1400

1600

1800

2000TDA1

TDA2

TDA3

AMS62C

S 2p

Physical & Chemical Analysis

Electrode Fabrication0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 50 100 150 200 250 300 350 400 450 500

Electrochemical Analysis-0.005

-0.004

-0.003

-0.002

-0.001

0

0.001

0.002

0.003

0.004

0.005

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0

Potenial (V)

Cur

rent

(A)

1.922040PitchKuraray NK260

1.991939Fructose, GlucoseTDA-AMS 62 C

2.352265Fructose, GlucoseTDA3

1.902114SucroseTDA2

2.042053SucroseTDA1

2.951796Pine Saw DustPica BP-10

3.49969PeatNorit SX-Ultra

2.051989Coconut ShellNorit Supra 50

2.991622Mixed HardwoodMeadWestvaco Nuchar RGC

2.381479Coconut ShellKuraray YP-18X

2.031516Coconut ShellKuraray YP-17D

1.941318Phenolic ResinKuraray RP-15

Unknown2,000*ProprietaryW.L. Gore

4.14402Resorcinol FormaldehydeMarkekTech International Aerogel Cloth

Average Pore Size (nm)

BET Surface Area (m2/g)

PrecursorCarbon

Analysis of Carbon Powders

* Supplied by manufacturer.

Surface Composition of Carbons Determined by XPS

0.00400.00.370.0099.63HOPG

0.05710.60 (Na)5.350.3493.70TDA-AMS62C

0.05490.005.190.2494.58TDA-3

0.06380.61 (S)5.901.0592.44TDA-2

0.04980.07 (S)4.720.3494.87TDA-1

0.06330.05.940.2493.82Pica BP-10

0.03590.44 (Na)3.440.4295.70Norit SX Ultra

0.05430.53 (Na)5.110.3394.03Norit DLC Supra 50

0.04930.004.690.1195.20Mead Westvaco Nuchar RGC

0.06430.97 (Na)0.13 (S)

5.950.4492.5Kuraray NK-260

0.08660.007.950.2591.80Kuraray YP-18X

0.07030.006.540.4193.05Kuraray YP-17

0.11840.0010.490.9088.61Kuraray RP-15

0.06161.24 (Na)5.720.2092.83Aerogel

Ratio (O/C)At% Na or SAt% OAt% NAt% CCarbon Material

Carbons as received. No heat treatment.

Experimental Carbons-Electrode Fabrication

Limited quantities of sampleFabricated at NSWCDoctor Blade ProcessBinder: PolyvinylideneFluoride (Kynar ®)Thickness: 12-14µm 2” x 3” electrodes

Sufficient quantities of carbon samplesElectroflex® ProcessUltrahigh molecular weight polyethyleneUses extrusion, calendaring and extraction technology.Films 50-500 µm thick, 21 cm wide.

Robert Waterhouse, Amtek Research International

Commercially Available Carbons-Electrode Fabrication

GORE® EDLC electrodes Activated carbon/polytetrafluoroethylene(PTFE) compositeThickness: 80 -1000µm Width: 25 - 200 mm

David Zuckerbrod, W.L. Gore & Associates

Commercially Available Electrodes- Fabrication

2.121.9212852040PitchKuraray NK260

2.041.9915981939Fructose, GlucoseTDA-AMS 62 C

2.332.3511312265Fructose, GlucoseTDA3

Not Avail.1.90Not avail.2114SucroseTDA2

2.042.0415882053SucroseTDA1

3.152.9510371796Pine Saw DustPica BP-10

4.353.49475969PeatNorit SX-Ultra

2.092.0511981989Coconut ShellNorit Supra 50

3.102.9911471622Mixed HardwoodMeadWestvaco Nuchar RGC

2.472.3810181479Coconut ShellKuraray YP-18X

2.082.039161516Coconut ShellKuraray YP-17D

1.961.949371318Phenolic ResinKuraray RP-15

2.03Unknown18452,000*ProprietaryW.L. Gore

7.614.14336402Resorcinol Formaldehyde

MarkekTech International Aerogel Cloth

ElectrodePowderElectrodePowder

Average Pore Size(nm)

BET Surface Area(m2/g)PrecursorCarbon

Analysis of Carbons & Electrodes

154148Kuraray NK-260 (80)

10610099TDA-AMS 62C (81)

92

98

90

58

87

90

92

99

168

1M TEATFBAN

(F/g)

147139W.L. Gore (83)

91104TDA-3 (81)

101113TDA-2 (81)

86100TDA-1 (81)

8077Pica BP-10 (80)

5552Norit SX-Ultra (80)

8176Norit Supra 50 (80)

8286MeadWestvaco Nuchar RGC (80)

8883Kuraray YP-17D (80)

9287Kuraray YP-18X (84)

9083Kuraray RP-15 (92)

2822MarkeTech Aerogel Cloth (100)

2M LiBF4AN

(F/g)

1M LiPF6 50%EC:50%EMC

(F/g)Carbon

(% Active Carbon Material)

Results of Symmetric EDLC Tests50th discharge, 2” X 3” cells charged at 1mA/cm2 and discharged at 10mA/cm2

9.5 mS/cm 54.6 mS/cm17.3 mS/cm

Cell0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 50 100 150 200 250 300 350 400 450 500

Three-Electrode Evaluation to Determine Limiting Electrode

Cell

Negative Electrodevs. Li Reference

Positive Electrodevs. Li Reference

(Gore Electrode, 1M LiPF6 Dissolved in 50% Ethylene Carbonate: 50% Ethylmethyl Carbonate)

Volta

ge (V

)

50th Discharge Time (sec)

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350 400 450 500

50th Discharge Time (sec.)

Volta

ge (V

)

Cell

Positive Electrodevs. Li Reference

- (Negative Electrodevs. Li Reference)

(Gore, 1M LiPF6 Dissolved in 50% Ethylene Carbonate: 50% Ethylmethyl Carbonate)

Three-Electrode Evaluation to Determine Limiting Electrode

½ Cell CV Experiments

1M NEt4 BF4 in AN (1/2 cell Anode Exp)

-0.006

-0.005

-0.004

-0.003

-0.002

-0.001

0

0.001

0.002

0.003

0.004

0.005

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0

Potential (V)

Cur

rent

(A)

1M NEt4 BF4 in AN 1/2 Cell Cathode Exp

-0.008

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

0 0.2 0.4 0.6 0.8 1 1.2

Potential (V)

Cur

rent

(I)

2M Li BF4 in AN

-0.005

-0.004

-0.003

-0.002

-0.001

0

0.001

0.002

0.003

0.004

0.005

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0

Potenial (V)

Cur

rent

(A)

2M LiBF4 in AN

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

0.01

0 0.2 0.4 0.6 0.8 1 1.2

Potential (V)

Cur

rent

(A)

1M NEt4 BF4 in AN

2M Li BF4 in AN

NegativeNEt4+: 93 F/g

PositiveBF4

-: 109 F/g

Mead Westvaco Nuchar RGC

NegativeLi+: 70 F/g

PositiveBF4

-: 94 F/g

Results Suggests…Cell is limited by negative electrode.Ionic Radius (no solvation):

NEt4+ : 3.4 - 3.7 ÅLi+: 0.8 - 1.2 ÅBF4

-: 2.3 - 2.4 ÅLi+ solvation sphere radius must be larger than NEt4+

solvation sphere. For same charge species: As radius decreases hydration (solvation) energy increases.

+-Power Supply

+

++

+

-

++

+

+

-

------

Solvated Anion

+

+

Solvated Cation+

+Li+ NEt4+

Cotton and Wilkinson

154148Kuraray NK-260 (80)

10610099TDA-AMS 62C (81)

92

98

90

58

87

90

92

99

168

1M TEATFBAN

(F/g)

147139W.L. Gore (83)

91104TDA-3 (81)

101113TDA-2 (81)

86100TDA-1 (81)

8077Pica BP-10 (80)

5552Norit SX-Ultra (80)

8176Norit Supra 50 (80)

8286MeadWestvaco Nuchar RGC (80)

8883Kuraray YP-17D (80)

9287Kuraray YP-18X (84)

9083Kuraray RP-15 (92)

2822MarkeTech Aerogel Cloth (100)

2M LiBF4AN

(F/g)

1M LiPF6 50%EC:50%EMC

(F/g)Carbon

(% Active Carbon Material)

Results of Symmetric EDLC Tests50th discharge, 2” X 3” cells charged at 1mA/cm2 and discharged at 10mA/cm2

9.5 mS/cm 54.6 mS/cm17.3 mS/cm

?

Binding Energy (eV)160162164166168170

Inte

nsity

(cou

nts/

seco

nd)

600

800

1000

1200

1400

1600

1800

2000TDA1

TDA2

TDA3

AMS62C

S 2p

0.0570.00 (0.60)

0.345.3593.70TDA AMS 62C

.00040.000.000.3799.63HOPG

0.0550.000.245.1994.58TDA3

0.0640.611.055.9092.44TDA2

0.0500.070.344.7294.87TDA1

O/C Ratio

At% S (Na)

At% N

At% O

At% CSample

XPS Results

Sulfur 2pTDA Carbons Analysis

Binding Energy (eV)02004006008001000

x105

Inte

nsity

(cou

nts/

seco

nd)

0

1

2HOPG

TDA1

TDA2

TDA3

AMS62C

C

ON

S Si

O(KLL)

C(KVV)

Na

5 nanometer XPS penetration

Effect of C Powder Surface Area on Specific Capacitance

0

20

40

60

80

100

120

140

160

180

0 500 1000 1500 2000 2500

Carbon Powder Surface Area (m2/g)

Cap

acita

nce

(F/g

of A

ctiv

e C

)

1M LiPF6 in 50%EC, 50%EMC 2M LiBF4 in AN

(50th Discharge, D:10mA/cm2, C:1mA/cm2)

Effect of Electrode Surface Area on Specific Capacitance

0

20

40

60

80

100

120

140

160

180

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Electrode Surface Area (m2/g)

Cap

acita

nce

(F/g

Act

ive

C)

1M LiPF6 50% EC/50%EMC 2M LiBF4 in AN

(50th Discharge, D:10mA/cm2, C:1mA/cm2)

Results of Symmetric EDLC Tests50th discharge, 2” X 3” cells charged at 1mA/cm2 and discharged at 10mA/cm2

4338Kuraray NK-260 (80)

373535TDA-AMS 62C Doctor Blade (81)

25

33

31

22

29

30

59

66

1M TEATFBAN

(F/cc)

5855W.L. Gore (83)

22 32TDA-3 Doctor Blade (81)

3332TDA-2 Doctor Blade (81)

29 36TDA-1 Doctor Blade (81)

2627Pica BP-10 (80)

2117Norit SX-Ultra (80)

2725Norit Supra 50 (80)

1920MeadWestvaco Nuchar RGC (80)

2926Kuraray YP-17D (80)

4742Kuraray YP-18X (84)

5651Kuraray RP-15 (92)

1711MarkeTech Aerogel Cloth (100)

2M LiBF4AN

(F/cc)

1M LiPF6 50%EC:50%EMC

(F/cc)Carbon

(% Active Material)

139

87

113

F/g

148

Effect of Electrode Surface Area on Volumetric Capacitance

(50th Discharge, D:10mA/cm2, C:1mA/cm2)

0

10

20

30

40

50

60

70

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Electrode Surface Area (m2/g)

Cap

acita

nce

(F/c

c El

ectr

ode)

1M LiPF6 in 50%EC/50%EMC 2M LiBF4 in AN

AMTEK, Doctor Blade (80-81%)

W.L. Gore(83%)

AMTEK (92%)

AMTEK (84%)

MarkeTech (100%)

Electrode Processing is Important!

Voltage Decay

1.4

1.6

1.8

2

2.2

2.4

2.6

0 5 10 15 20

Rest Time (Hours)

Volta

ge (v

olts

)

Mead Westvaco Norit DLC Supra 50 Kuraray YP-17 Kuraray YP-18X

Pica BP10 (10mil) Kuraray RP-15 Gore Electrode

Causes of Voltage DecayMechanical short (e.g. fibrils piercing separator)Metal impurities (e.g. Fe+3, Fe+2) and adsorbed O2 that can be reduced and re-oxidized.Oxygen functional groups, commonly residing on the edges of graphitic particles undergoing redox reactions. Amount and type depend on manufacturing conditions:

- Basic Groups: formed after heating C in a vacuum or inert air then exposing to O2 on cooling.- Acid Groups: formed when C treated with O2 at high temperatures (400 to 500oC)

1. carboxyl, 2. phenolic, 3. quinone, 4. lactone, 5. carboxyl anhydride, 6. peroxide

C-H Kim and S-I Pyun, J Korean Ceramic Soc., 40, 819 (2003)

Groups Can React with Electrolyte Increasing Cell Impedance

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

1 week rt +1 wk 60C 2wks 60C 3wks 60C 4 wks 60C 5 wks 60C

cycling conditions

impe

danc

e (m

ohm

/cm

2)

MK 231MK261

NK 331NK 260

Impedance of Li4Ti5O12/C Cells Using Different Carbons2M LiBF4 in AN, 2.5V constant storage, 60oC

Impedance of hybrid cells comparing different carbons

0.00

1.00

2.00

3.00

4.00

5.00

6.00

1 w eek rt +1 w k 60C 4 w ks 60C

cycling conditions

impe

danc

e (m

ohm

/cm

2)

MK 231

MK 261

ASupra

Commercial

NK 331

NK 260

Impedance of Li4Ti5O12/C Cells Using Different Carbons

2M LiBF4 in AN, 2.5V constant storage, 60oC

SummaryNSWC-Carderock collaborating with Rutgers University in developing non-aqueous asymmetric hybrid DLCs for load leveling applications.Capacitance of thirteen carbons using two lithium based electrolytes determined.

Greatest capacitance achieved with W.L. Gore Carbon and Kuraray NK-260.Electrode processing is important.

Cells containing 2M LiBF4 in AN electrolyte generally:Gave 5% higher capacitance (F/g) than cells containing 1M LiPF6 in EC/EMC.Exception: TDA-1, TDA-2, TDA-3 displayed highest capacitance with 1M LiPF6 EC/EMC.

Efforts underway to determine:Why TDA carbons utilizing carbonate electrolytes yielded higher capacitance than NEt4BF4 in ANRole of C’s surface functional groups on self-discharge.

Acknowledgements

My colleagues, Mrs. Michelle Cervenak, Dr. Azzam Mansour, & Dr. Glenn Zoski

Dr. Glenn Amatucci, Rutgers University

Dr. Michele Anderson, ONR