High Surface Area Electrodes Derived from Polymer Wrapped Carbon

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High surface area electrodes derived from polymer wrapped carbon nanotubes for enhanced energy storage devices Amir Ahmad Bakhtiary Davijani, Hsiang-Hao Clive Liu, Kishor Gupta, and Satish Kumar ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b08845 • Publication Date (Web): 24 Aug 2016 Downloaded from http://pubs.acs.org on August 25, 2016

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ACS Applied Materials & Interfaces

High surface area electrodes derived from polymer wrapped carbon nanotubes for enhanced energy storage devices Amir A Bakhtiary Davijani, H Clive Liu, Kishor Gupta, Satish Kumar* School of Materials Science and Engineering Georgia Institute of Technology Atlanta GA, USA 30332-0295 *Corresponding author: [email protected] Abstract Electrical double layer capacitors store energy on two adjacent layers, resulting in fast charging and discharging, but their energy density is limited by the available surface area. In this study, using poly(methyl methacrylate) assisted sonication, carbon nanotube buckypapers with specific surface area as high as 950 m2/g have been processed. Performance of these high surface area buckypapers have been evaluated as supercapacitor electrodes. The energy density of these high surface area electrodes at low power density of 0.68 kW/kg was 22.3 Wh/kg, and at high power density of 84 kW/kg, it was 3.13 Wh/kg using the ionic liquid electrolyte. Keywords: Carbon nanotubes, Supercapacitors, High surface area, Poly(methyl methacrylate), Polymer wrapping

Introduction Supercapacitors or electric double layer capacitors (EDLCs) are suitable for high power applications, as they can provide quick bursts of energy in short durations. Carbon based materials in a variety of dimensions, including activated carbon,1-3 graphene4-6 and carbon

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nanotubes (CNT),7, 8 in various forms, such as powders,9 gels,10-12 and composites,13-15 have been commercially used and/or scientifically studied for energy storage applications. Activated carbon, due to its low cost, porous structure and high specific surface area (SSA), is widely used in commercial supercapacitors. Energy storage is expected to increase linearly with surface area if all pores are accessible to the electrolyte. Any deviation from this relation is attributed to psuedocapacitance or inaccessibility of the electrolyte to the pores. Lin et al. concluded that pores smaller than 0.8 nm do not contribute to the double layer capacitance.10 The importance of larger pores has been highlighted in other studies, confirming that pores accessible to electrolyte ions at low charge/discharge rates may not be accessible at higher rates.16, 17 In recent years there has been substantial focus on tailoring the porous structure of carbon materials to improve capacitance and rate performance.18 Microporous, mesoporous and macroporous carbon materials have been synthesized by physical or chemical activation, zeolite and silica templating, and by carbonization of polymer blends and organic aerogels.19,

20

A

microporous doped carbon structure synthesized using zeolite templates exhibited a capacitance of 300 F/g at 0.1 A/g, and the capacitance decreased by 25% after 10,000 charge/discharge cycles.21 Other forms of carbon such as CNTs and graphene which have high electrical conductivity, porous structure and high surface area are suitable candidates for EDLCs. Both of these materials suffer from aggregation and agglomeration and thus in bulk form, result in significantly lower surface area than theoretically predicted, and this effects their supercapacitor performance. As a result, different techniques have been used to increase their surface area and supercapacitor performance.3,

22-33

Hybrid structures of single wall carbon nanotubes (SWNT)

and graphene have been made to overcome aggregation, to increase SSA, and to enhance pore accessibility to the electrolyte.22-25 Adding functional groups to these carbon based materials also

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leads to increased capacitance due to contributions from pseudo capacitance.34, 35 Acid treatment, KOH activation and plasma treatment have been used to increase SSA by inducing defects and opening CNT tips.3, 26-32 There has been no study on the influence of CNT surface area on energy storage without inducing defects, opening them, or without adding functional groups. All these factors influence the pseudo capacitance of the CNT electrodes, and it is important to study the effect of surface area alone without the added contribution from pseudo capacitance. Theoretically, an individual SWNT has an SSA of 1313 m2/g, but in bulk materials made from SWNTs, such as buckypapers, the highest specific surface area reported to date is about 650 m2/g due to bundling.36 The highest SSA reported for densified SWNT forest is 1000 m2/g.37 Supercapacitors made using these aligned high surface SWNT forest resulted in capacitance of 14.25 F/g at 1 A/g (which corresponds to specific capacitance of 57 F/g) in 1 M Et4NBF4/propylene carbonate electrolyte. Previously, we reported that the process of buckypaper formation from SWNT via poly(methyl methacrylate) (PMMA) wrapping prevents SWNT aggregation and results in significantly enhanced surface area.38 PMMA helically wraps SWNTs in an ordered manner that results in a strong diffraction peak in the wide angle X-ray diffraction (WAXD). This strong diffraction peak corresponds to the pitch of PMMA helix wrapped along the SWNT length. Using few wall carbon nanotubes (FWNT) and SWNTs, and this novel PMMA wrapped processing scheme, buckypapers with specific surface area in the range of 300 to 950 m2/g have been fabricated in this study and their supercapacitor performance has been characterized. The PMMA wrapping alters the SWNT porous structure by preventing SWNT bundling and by acting as a sacrificial component. The high surface area SWNT films exhibit high energy density at ultrahigh power density, significantly surpassing the performance of recently developed CNT and CNT/graphene based EDLCs.22, 39



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Experimental Materials HiPcoTM SWNTs (grade SP300, average diameter 0.9 nm, purity 98%) and few wall CNTs (FWNTs) (grade XOC231U, average diameter 2.7 nm, mainly two and three walled, purity 98.8%) were obtained from Carbon Nanotechnologies, Inc. Dimethylformamide (DMF, ACS grade, 99.8% purity) and PMMA (Mw= 350,000 g/mol) polymer were obtained from Sigma Aldrich. PTFE membrane (Zefon International, FPTPT147) with 1 µm pore size was used for the filtration. Sample preparation A suspension containing 8 mg SWNT in 100 ml DMF was homogenized (IKA ULTRATURRAX T18) for 30 minutes and then 80 mg PMMA (dissolved in 40 ml DMF) was added to this SWNT/DMF suspension. After vigorous shaking, this PMMA/SWNT/DMF suspension was sonicated for 24 hours (Branson 3510R-MT, 100 W, 42 kHz). The suspension was filtered using the PTFE membrane and washed with methanol to remove DMF. The PMMA/SWNT buckypaper was peeled from the PTFE membrane and dried in vacuum oven at 70 °C for three days. The PMMA in the buckypaper was removed by heating to 400 °C at 10 °C/min under nitrogen and then by holding at 400 °C for 5 minutes. It is noted that under these conditions, PMMA completely burns out and does not leave any carbon residue, and at the same time SWNTs are not affected (Figure S1).38 The resulting sample is referred to as high-surface SWNT (HS-SWNT) buckypaper. SWNT and FWNT buckypapers were also made without the aid of PMMA. For these buckypapers, SWNT was dispersed at 1.3 mg/100 ml in DMF and sonicated for 24 hours. FWNT was dispersed at 1.3 mg/100 ml in DMF and sonicated for 5 minutes. Both


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the SWNT and FWNT suspensions were filtered using the PTFE membrane, washed in methanol, and the dried in vacuum at 70 °C for three days. 1.1 Characterization For surface area and pore size analysis, isothermal N2 gas adsorption study was carried out on various buckypapers using ASAP 2020 (Micromeritics Inc.) at 77 K. BET and BJH theories were used to obtain the specific surface area and pore size distribution, respectively. Scanning electron microscopy (SEM) was performed on a Hitachi SU8010 at an accelerating voltage of 5 kV. SEM was done on buckypapers without any metal coating. X-ray photoelectron spectroscopy (XPS) (Thermal Scientific K-alpha XPS instrument) was employed to analyze the buckypaper chemical composition. Raman spectroscopy on the buckypapers was carried out using 785 nm laser HORIBA XploRA Raman Microscope System. Galvanostatic constant current (CC) charging-discharging and cyclic voltammetry (CV) measurements were carried out on Solartron 1470 at room temperature, using two film electrodes. Electrode diameter, thickness and mass were approximately 6.4 mm, 15 µm, and 0.3 mg, respectively. Electrical conductivity of the buckypapers was measured by a four-point probe configuration (Signatone). The electrodes were free standing and completely composed of CNTs without any binding material (Table S1). The electrode density was 0.63 ± 0.02 g/cm3, and the electrodes were separated by Celgard 3400 microporous membrane and were sandwiched between two stainless steel current collectors. KOH aqueous solution (6 M) with potential range of 0 to 1 V and 1-Ethyl-3methylimidazolium tetrafluoroborate (EMIMBF4) with a potential range of 0 to 3 V were used as the electrolytes. For the constant current measurements, the specific capacitance was obtained using ‫ܥ‬௦௣ =

ூ∆௧

(

ଵ

∆௏ ௠భ

ଵ

+ ௠ ) where I is the current, m1 and m2 are the masses of the two electrodes, మ

∆t is the discharge time, ∆V is the discharge voltage during that time. Determination of ∆t/∆V 5 ACS Paragon Plus Environment


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excludes the IR drop occurring at the beginning of the discharge. The energy density was calculated using ‫= ܧ‬

‫ ׬‬௏ூௗ௧ , ௠భ ା௠మ

and power density is ܲ =

ா ௧೏

, where td is the total discharge time.

The specific capacitance of the cyclic voltammetry measurements of each electrode was obtained using ‫ܥ‬௦௣ =

‫ ׬‬ூௗ௏ ଵ ( ଶோ∆௏ ௠భ

+

ଵ ௠మ

) , where the integral is the area enclosed in the V-I plot, R is the CV

scan rate and ∆V is the potential window.

Results and Discussions Porosity The buckypaper made from FWNT had the SSA of 300 m2/g, and the one made from SWNT without the aid of PMMA had the SSA of 650 m2/g. The highest surface area SWNT buckypaper obtained with the aid of PMMA, exhibited the surface area of 950 m2/g, and this buckypaper is denoted as HS-SWNT buckypaper (Figure 1). The SWNT has lower SSA than HS-SWNT, as in the absence of PMMA, nanotubes re-bundle after sonication. The increase of SSA for the PMMA processed SWNT buckypaper compared to the buckypaper without the use of PMMA, supports the hypothesis that PMMA wrapping (Figure 2) results in smaller diameter SWNT bundles and hence higher specific surface area, after PMMA has been removed. HSSWNT, not only shows higher surface area than SWNT and FWNT buckypapers, but it also shows higher pore volume (Figure 3). The data presented in Figure 3 shows that the higher pore volume was mostly due to micro and mesopores, with sizes in the range of 1 to 11 nm.


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HS-SWNT

800 700 600 500

SWNT

400 300 200 100

FWNT

0 0.0

0.2

0.4

0.6

0.8

1.0

Relative Pressure (p/p°)

Figure 1. N2 gas adsorption isotherms of FWNT, SWNT, and HS-SWNT buckypapers at 77 K.

Figure 2. PMMA wrapping around SWNTs prevent them from aggregating. Micropores are created when the wrapped PMMA from adjacent SWNTs is removed.

FWNT SWNT HS-SWNT

60 50 40 30 20 10

b Pore volume (cm3/g)

a Surface Area (m2/g)

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Quantity Adsorbed (cm³/g STP)

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0

FWNT SWNT HS-SWNT

0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00

1

10

1

Pore Width (nm)

10

Pore Width (nm)


100


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Figure 3. (a) Surface area, and (b) pore volume as a function of Pore size as determined from BJH theory. SEM images of the three buckypaper (FWNT, SWNT, and HS-SWNT) surfaces are given in Figure 4. The average CNT bundle diameters for FWNT, SWNT and HS-SWNT buckypapers measured from these images, using ImageJ software, are 22 ± 10 nm, 9 ± 4 nm, and 3 ± 2 nm respectively. These bundle diameters are qualitatively consistent with the surface area values measured from the nitrogen gas adsorption. In other words, as expected, buckypapers with low surface area have large bundle diameter and vice-versa.

b

a

c

Figure 4. SEM images of (a) FWNT, (b) SWNT, and (c) HS-SWNT buckypapers. Nitrogen gas adsorption behavior of these three buckypapers is shown in Figures 1.


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Electrochemical performance The CC charge-discharge plots of the three different types of electrodes (FWNT, SWNT, and HS-SWNT) are shown in Figure S2. The specific capacitance and energy density values obtained from the CC measurements are given in Figure 5a and 5b. The capacitance and energy density decrease with increasing current density. The energy density was calculated directly from ଵ

current, voltage and discharge time, rather than from capacitance (‫ ܸܥ = ܧ‬ଶ ), as sometimes ଶ

done. Thermogravimetric analysis shows that PMMA is completely removed under the heat treatment conditions used for HS-SWNT processing, and there is no degradation and/or functionalization of SWNT (Figure S1).38 This has also been confirmed by Raman spectroscopy and XPS. Raman G/D ratio for both SWNT and HS-SWNT was ~11 (Figure S3). Presence of any amorphous carbon or SWNT functionalization would have resulted in a decreased G/D ratio, but this has not been observed. XPS data show that the C/O ratio in both SWNT and HS-SWNT buckypapers is also the same (table S2, Figure S4). This confirms that the enhanced energy storage of HS-SWNT was only due to its higher surface area as compared to SWNT. Figure 5c shows the IR drop for each electrode as a function of current density, and shows that among the three types of electrodes studied in this work, at a given current density HS-SWNT shows much lower IR-drop, as compared to SWNT and FWNT electrodes. Lower internal resistance of the HS-SWNT capacitor suggests that the electrolyte is more readily accessible to various pores in HS-SWNT, as compared to SWNT and FWNTs, even at high current densities. This is despite the fact that HS-SWNT has lower electrical conductivity than SWNT (Table S1), and this reinforces the idea that ion mobility is an important factor. The CV measurements do not show an oxidation peak, confirming the absence of pseudo capacitance (Figure 6a and Figure S5). HS-



SWNT electrode exhibited good rate capability, with a capacitance of 23 F/g at a high rate of 50 V/s (Figure 6b).

a 100

b Energy Density (Wh/kg)

FWNT SWNT HS-SWNT

90

Capacitance (F/g)

80 70 60 50 40 30 20 10

FWNT SWNT HS-SWNT

2.5 2.0 1.5 1.0 0.5

0 0.1

1

10

0.1

100

c

1

10

100

Current Density (A/g)


IR drop (V)

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1

0.1

FWNT SWNT HS-SWNT

0.01

0.001 0.1

1

10

100

1000


Figure 5. Evaluation of the electrochemical performance of FWNT, SWNT and HS-SWNT electrodes in KOH electrolyte. (a) Specific capacitance as a function of current density. (b) Energy density as a function of current density. (c) IR-drop of the electrodes as a function of current density.


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0.5 V/s 1 V/s 2 V/s

40 30 20 10 0 -10 -20 -30 -40

50 V/s

250

b Current density (A/g)

a Current density (A/g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


200 150 100 50 0 -50 -100 -150 -200

-50 0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

E (V)

0.4

0.6

0.8

1.0

E (V)

Figure 6. Cyclic voltammetry of HS-SWNT in KOH electrolyte at various scan rates, (a) 0.5, 1 and 2 V/s, and (b) 50 V/s. For EDLCs, if the entire surface area is accessible, then capacitance should increase linearly with SSA. PMMA processing of SWNTs repeatedly produced buckypapers with specific surface area above 900 m2/g. Measurements of 11 PMMA processed buckypapers yielded an average specific surface area of 943 ± 69 m2/g (nitrogen gas adsorption isotherms for these 11 samples are shown in Figure S6). Two trials using PMMA, resulted in buckypapers with surface areas of 805 and 870 m2/g, and these were also tested for their performance as supercapacitor electrode. Thus in total five electrodes were tested with surface area in the range of 300 to 950 m2/g, and their specific capacitance as a function of specific surface area are plotted at 5 and 100 mV/s in Figure 7, showing reasonable correlation within experimental error.



b

FWNT SWNT

120 100

120

Capacitance (F/g)

a Capacitance (F/g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

80 60 40

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FWNT SWNT

100 80 60 40 20

20 0 300 400 500 600 700 800 900 1000

300 400 500 600 700 800 900 1000

SSA (m2/g)

SSA (m2/g)

Figure 7. Buckypaper capacitance as a function of specific surface area (SSA) measured using 6 M KOH electrolyte at (a) 5 mV/s and (b) 100 mV/s. Typical of CNT electrodes, the HS-SWNT displayed excellent capacitance retention after 10000 charge-discharge cycles (Figure 8a). The HS-SWNT electrode was also tested using ionic liquid electrolyte, EMIMBF4. CC, CV plots and cycling stability of HS-SWNT using ionic electrolyte are given in Figure S7-S9. The Ragone plots of the HS-SWNT electrodes based on EMIMBF4 and KOH electrolyte tests area given in Figure 8b. As expected, due to large potential window, the energy density is about 9 times higher using the EMIMBF4 electrolyte than 6 molar KOH electrolyte.


a

Power Density (W/cm3) Energy Density (Wh/kg)

b 120

Retention (%)

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100 80 60 40 20 0 0

0.064

0.64

6.4

64

10

6.4

1

2500 5000 7500 10000

0.64

KOH EMIMBF4

0.1

Number of cycles

1

Energy Density (mWh/cm3)

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10

100

Power Density (kW/kg)

Figure 8. (a) Capacitance retention of HS-SWNT electrode with 6 M KOH electrolyte for 10000 charge - discharge cycles. The cell was charged and discharged at a rate of 1 A/g. (b) Ragone plots (in gravimetric and volumetric units) of HS-SWNT electrodes using 6M KOH and EMIMB4 electrolytes. Considering actual applications, packaging and size of the energy storage device are also important factors. If the volumetric capacitance is too low, then a large electrode volume will be required for storing certain amount of charge. This may not always be practical. Therefore, along with high gravimetric capacitance, a high electrode density is often required. The density of the HS-SWNT film was 0.63±0.02 g/cm3. Since supercapacitors are primarily used for high power applications, the HS-SWNT provides excellent performance. To demonstrate the performance of the HS-SWNT, a Ragone plot is presented in Figure 9, comparing the performance of HS-SWNT with recent best literature data on SWNT and graphene electrodes. This includes a commercial 3.5 V/25 mF activated carbon supercapacitor, CNT/graphene,22 laser scribed graphene,39 carbon onion micro-supercapacitor,40 and mechanically densified SWNT forest41 electrodes. The volumetric energy density of HS-SWNT electrode is significantly higher than the previously reported high energy density of CNT or graphene based supercapacitors with no 13 ACS Paragon Plus Environment


pseudocapacitance at the very high power density. Pseudocapacitance results in high capacitance and energy density but low power density. For example, high density porous graphene macroform (HPGM), which has a density of 1.58 g/cm3, has a capacitance of 106 F/g at 0.5 A/g and delivers an energy density of 23.1 Wh/kg at a power density of 0.31 kW/kg.42 Micro-supercapacitors have gained attention due to their application as power sources in micro-electrical systems. Micro-supercapacitors can also be made using the current technique, as the PMMA wrapped SWNTs can be deposited on any substrate. The simple processing method for achieving high surface area SWNT buckypapers with record high energy and power densities, makes this method an excellent candidate for future commercial applications.

Densified SWNT forest

Energy Density (mWh/cm3)

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10

HS-SWNT

Graphene/CNT

LSG

1

Carbon onion

3.5V/25mF supercapacitor

0.1 0.01

1

100

Power Density (W/cm3)

Figure 9. Ragone plot of HS-SWNT using EMIMBF4 electrolyte. For comparison, commercial 3.5 V/25 mF activated carbon supercapacitor (total device volume),40 carbon onion microsupercapacitor,40 laser scribed graphene (LSG, organic electrolyte 0-3 V) supercapacitor,39 mechanically densified SWNT forest (ionic liquid electrolyte 0-3 V),41 and graphene/CNT (ionic liquid electrolyte)22 micro-supercapacitor Ragone plots are also given. Please note that all the


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data in this figure is based on the volume of the electrode except for the commercial supercapacitor, which is based on the total volume of the device.

Conclusion Carbon nanotube supercapacitor electrodes with specific surface area in the range of 300 to 950 m2/g were fabricated to understand the influence of surface area on energy storage. This was achieved without introducing defects or functionalizing the nanotubes, and thus all the electrodes exhibited no pseudo capacitance. The SWNT buckypaper with a surface area of 950 m2/g (referred to as HS-SWNT buckypaper) exhibited high energy density of 3.13 kWh/kg at a high power density of 84 kW/kg. Supporting Information: Adsorption isotherms, electrochemical measurements, XPS, TGA, Raman spectroscopy Acknowledgement: This work is supported by a grant from the Air Force Office of Scientific Research (FA9550-09-1-0150 and FA9550-14-1-0194). Assistance of Kumar group members in this study is gratefully acknowledged. References (1)

Endo, M.; Maeda, T.; Takeda, T.; Kim, Y. J.; Koshiba, K.; Hara, H.; Dresselhaus, M. S. Capacitance and Pore-Size Distribution in Aqueous and Nonaqueous Electrolytes Using Various Activated Carbon Electrodes. J. Electrochem. Soc. 2001, 148, A910-A914.

(2)

Qu, D. Studies of the Activated Carbons Used in Double-Layer Supercapacitors. J. Power Sources 2002, 109, 403-411.

(3)

Jiang, Q.; Qu, M. Z.; Zhou, G. M.; Zhang, B. L.; Yu, Z. L. A Study of Activated Carbon Nanotubes as Electrochemical Super Capacitors Electrode Materials. Mater. Lett. 2002, 57, 988-991.



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(4)

Page 16 of 20

Vivekchand, S. R. C.; Rout, C.; Subrahmanyam, K. S.; Govindaraj, A.; Rao, C. N. R. Graphene-Based Electrochemical Supercapacitors. J. Chem. Sci. 2008, 120, 9-13.

(5)

Stoller, M. D.; Park, S.; Zhu, Y.; An, J.; Ruoff, R. S. Graphene-Based Ultracapacitors. Nano Lett. 2008, 8, 3498-3502.

(6)

Wang, Y.; Shi, Z.; Huang, Y.; Ma, Y.; Wang, C.; Chen, M.; Chen, Y. Supercapacitor Devices Based on Graphene Materials. J. Phys. Chem. C 2009, 113, 13103-13107.

(7)

Niu, C.; Sichel, E. K.; Hoch, R.; Moy, D.; Tennent, H. High Power Electrochemical Capacitors Based on Carbon Nanotube Electrodes. Appl. Phys. Lett. 1997, 70, 1480.

(8)

Frackowiak, E.; Jurewicz, K.; Delpeux, S.; Beguin, F. Electrochemical Application of Carbon Nanotubes. In Low-Dimensional Systems: Theory, Preparation, and Some Applications, Liz-Marzán, L.; Giersig, M., Eds. Springer Netherlands: 2003; Vol. 91, pp 305-318.

(9)

Gamby, J.; Taberna, P. L.; Simon, P.; Fauvarque, J. F.; Chesneau, M. Studies and Characterisations of Various Activated Carbons Used for Carbon/Carbon Supercapacitors. J. Power Sources 2001, 101, 109-116.

(10) Lin, C.; Ritter, J. A.; Popov, B. N. Correlation of Double-Layer Capacitance with the Pore Structure of Sol-Gel Derived Carbon Xerogels. J. Electrochem. Soc. 1999, 146, 3639-3643. (11) Garcia, B. B.; Candelaria, S. L.; Liu, D.; Sepheri, S.; Cruz, J. A.; Cao, G. High Performance High-Purity Sol-Gel Derived Carbon Supercapacitors from Renewable Sources. Renewable Energy 2011, 36, 1788-1794. (12) Li, W.; Reichenauer, G.; Fricke, J. Carbon Aerogels Derived from Cresol–Resorcinol–Formaldehyde for Supercapacitors. Carbon 2002, 40, 2955-2959. (13) Zhou, C.; Liu, T.; Wang, T.; Kumar, S. PAN/SAN/SWNT Ternary Composite: Pore Size Control and Electrochemical Supercapacitor Behavior. Polymer 2006, 47, 5831-5837.


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(14) Kalpana, D.; Omkumar, K. S.; Kumar, S. S.; Renganathan, N. G. A Novel High Power Symmetric Zno/Carbon Aerogel Composite Electrode for Electrochemical Supercapacitor. Electrochim. Acta 2006, 52, 1309-1315. (15) Carlson, T.; Ordéus, D.; Wysocki, M.; Asp, L. E. Structural Capacitor Materials Made from Carbon Fibre Epoxy Composites. Compos. Sci. Technol. 2010, 70, 1135-1140. (16) Qu, D.; Shi, H. Studies of Activated Carbons Used in Double-Layer Capacitors. J. Power Sources 1998, 74, 99-107. (17) Tamai, H.; Kouzu, M.; Morita, M.; Yasuda, H. Highly Mesoporous Carbon Electrodes for Electric Double-Layer Capacitors. Electrochem. Solid-State Lett. 2003, 6, A214-A217. (18) Lim, E.; Jo, C.; Lee, J. A Mini Review of Designed Mesoporous Materials for Energy-Storage Applications: From Electric Double-Layer Capacitors to Hybrid Supercapacitors. Nanoscale 2016, 8, 7827-7833. (19) Lee, J.; Kim, J.; Hyeon, T. Recent Progress in the Synthesis of Porous Carbon Materials. Adv. Mater. 2006, 18, 2073-2094. (20) Gong, Y.; Wei, Z.; Wang, J.; Zhang, P.; Li, H.; Wang, Y. Design and Fabrication of Hierarchically Porous Carbon with a Template-Free Method. Sci. Rep. 2014, 4, 6349. (21) Ania, C. O.; Khomenko, V.; Raymundo-Piñero, E.; Parra, J. B.; Béguin, F. The Large Electrochemical Capacitance of Microporous Doped Carbon Obtained by Using a Zeolite Template. Adv. Funct. Mater. 2007, 17, 1828-1836. (22) Lin, J.; Zhang, C.; Yan, Z.; Zhu, Y.; Peng, Z.; Hauge, R. H.; Natelson, D.; Tour, J. M. 3-Dimensional Graphene Carbon Nanotube Carpet-Based Microsupercapacitors with High Electrochemical Performance. Nano Lett. 2013, 13, 72-78.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 20

(23) Zhu, Y.; Li, L.; Zhang, C.; Casillas, G.; Sun, Z.; Yan, Z.; Ruan, G.; Peng, Z.; Raji, A.-R. O.; Kittrell, C.; Hauge, R. H.; Tour, J. M. A Seamless Three-Dimensional Carbon Nanotube Graphene Hybrid Material. Nat. Commun. 2012, 3, 1225. (24) Pham, D. T.; Lee, T. H.; Luong, D. H.; Yao, F.; Ghosh, A.; Le, V. T.; Kim, T. H.; Li, B.; Chang, J.; Lee, Y. H. Carbon Nanotube-Bridged Graphene 3d Building Blocks for Ultrafast Compact Supercapacitors. ACS Nano 2015, 9, 2018-2027. (25) Fan, Z.; Yan, J.; Zhi, L.; Zhang, Q.; Wei, T.; Feng, J.; Zhang, M.; Qian, W.; Wei, F. A ThreeDimensional Carbon Nanotube/Graphene Sandwich and Its Application as Electrode in Supercapacitors. Adv. Mater. 2010, 22, 3723-3728. (26) Yoon, B.-J.; Jeong, S.-H.; Lee, K.-H.; Seok Kim, H.; Gyung Park, C.; Hun Han, J. Electrical Properties of Electrical Double Layer Capacitors with Integrated Carbon Nanotube Electrodes. Chem. Phys. Lett. 2004, 388, 170-174. (27) Lu, W.; Qu, L.; Henry, K.; Dai, L. High Performance Electrochemical Capacitors from Aligned Carbon Nanotube Electrodes and Ionic Liquid Electrolytes. J. Power Sources 2009, 189, 1270-1277. (28) Frackowiak, E.; Metenier, K.; Bertagna, V.; Beguin, F. Supercapacitor Electrodes from Multiwalled Carbon Nanotubes. Appl. Phys. Lett. 2000, 77, 2421-2423. (29) Frackowiak, E.; Delpeux, S.; Jurewicz, K.; Szostak, K.; Cazorla-Amoros, D.; Béguin, F. Enhanced Capacitance of Carbon Nanotubes through Chemical Activation. Chem. Phys. Lett. 2002, 361, 3541. (30) Jagannathan, S.; Chae, H. G.; Jain, R.; Kumar, S. Structure and Electrochemical Properties of Activated Polyacrylonitrile Based Carbon Fibers Containing Carbon Nanotubes. J. Power Sources 2008, 185, 676-684.


Page 19 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(31) Jagannathan, S.; Liu, T.; Kumar, S. Pore Size Control and Electrochemical Capacitor Behavior of Chemically Activated Polyacrylonitrile – Carbon Nanotube Composite Films. Compos. Sci. Technol. 2010, 70, 593-598. (32) Liu, T.; Sreekumar, T. V.; Kumar, S.; Hauge, R. H.; Smalley, R. E. SWNT/PAN Composite Film-Based Supercapacitors. Carbon 2003, 41, 2440-2442. (33) Shao, Y.; El-Kady, M. F.; Wang, L. J.; Zhang, Q.; Li, Y.; Wang, H.; Mousavi, M. F.; Kaner, R. B. Graphene-Based Materials for Flexible Supercapacitors. Chem. Soc. Rev. 2015, 44, 3639-3665. (34) Barisci, J. N.; G., W. G.; Baughman, R. H. Electrochemical Studies of Single-Wall Carbon Nanotubes in Aqueous Solutions. J. Electroanal. Chem. 2000, 488, 92-98. (35) Zhou, C.; Kumar, S.; Doyle, C. D.; Tour, J. M. Functionalized Single Wall Carbon Nanotubes Treated with Pyrrole for Electrochemical Supercapacitor Membranes. Chem. Mater. 2005, 17, 1997-2002. (36) Muramatsu, H.; Hayashi, T.; Kim, Y. A.; Shimamoto, D.; Kim, Y. J.; Tantrakarn, K.; Endo, M.; Terrones, M.; Dresselhaus, M. S. Pore Structure and Oxidation Stability of Double-Walled Carbon Nanotube-Derived Bucky Paper. Chem. Phys. Lett. 2005, 414, 444-448. (37) Futaba, D. N.; Hata, K.; Yamada, T.; Hiraoka, T.; Hayamizu, Y.; Kakudate, Y.; Tanaike, O.; Hatori, H.; Yumura, M.; Iijima, S. Shape-Engineerable and Highly Densely Packed Single-Walled Carbon Nanotubes and Their Application as Super-Capacitor Electrodes. Nat. Mater. 2006, 5, 987-994. (38) Bakhtiary Davijani, A. A.; Kumar, S. Ordered Wrapping of Poly(Methyl Methacrylate) on Single Wall Carbon Nanotubes. Polymer 2015, 70, 278-281. (39) El-Kady, M. F.; Strong, V.; Dubin, S.; Kaner, R. B. Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors. Science 2012, 335, 1326-1330. (40) Pech, D.; Brunet, M.; Durou, H.; Huang, P.; Mochalin, V.; Gogotsi, Y.; Taberna, P.-L.; Simon, P. Ultrahigh-Power Micrometre-Sized Supercapacitors Based on Onion-Like Carbon. Nat. Nanotechnol. 2010, 5, 651-654.



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Page 20 of 20

(41) Zhou, Y.; Ghaffari, M.; Lin, M.; Parsons, E. M.; Liu, Y.; Wardle, B. L.; Zhang, Q. M. High Volumetric Electrochemical Performance of Ultra-High Density Aligned Carbon Nanotube Supercapacitors with Controlled Nanomorphology. Electrochim. Acta 2013, 111, 608-613. (42) Tao, Y.; Xie, X.; Lv, W.; Tang, D.-M.; Kong, D.; Huang, Z.; Nishihara, H.; Ishii, T.; Li, B.; Golberg, D.; Kang, F.; Kyotani, T.; Yang, Q.-H. Towards Ultrahigh Volumetric Capacitance: Graphene Derived Highly Dense but Porous Carbons for Supercapacitors. Sci. Rep. 2013, 3, 2975.


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