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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