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Single-walled carbon nanotube embedded porous carbon nanofiber with enhanced electrochemical capacitive performance
Materials Letters 144 (2015) 123–126
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Single-walled carbon nanotube embedded porous carbon nanofiber with enhanced electrochemical capacitive performance Lin Cheng a,c, Junjia He a, Yu Jin b, Hongyuan Chen b, Minghai Chen b,n a
College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074, China Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, China c State Grid Electric Power Research Institute, Luoyu Road 143, Wuhan 430074, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 4 November 2014 Accepted 7 January 2015 Available online 15 January 2015
Active carbon nanofibers (CNFs) with porous structure show highly electrochemical double-layer capacitance for supercapacitors because of their large specific area. However, their poor crystallization induced the low conductivity, which could largely limit the electrochemical performance of the porous CNFs. In this research, porous CNFs with single-walled carbon nanotubes (SWCNTs) were prepared by electrospinning and high temperature carbonization. The introduction of SWCNTs into porous CNFs could largely enhance the conductivity of the porous CNF nanotextiles, thus the electrochemical performance of the composite nanotextile was largely enhanced. The specific capacitance of the composite could achieve 417 F/g at a current density of 0.5 A/g, and keep 193 F/g at the high current density of 10 A/g. Furthermore its specific capacitance could keep 96% after 2000 cycles of charge/ discharge at the current density of 10 A/g. This nanotextile could be a promising candidate for the binder-free and filler-free electrodes of high-performance supercapacitors. & 2015 Elsevier B.V. All rights reserved.
Keywords: Electrospinning Carbon nanotube Porous carbon nanofiber Energy storage and conversion
1. Introduction Supercapacitors (also called electrochemical capacitors (ECs)) could provide higher power and longer cyclic lifetime than batteries, thus could be widely used in numerous applications such as power sources in electrical vehicles and portable electronic devices [1]. Porous carbon with large specific area plays an important role as the electrodes of the electrochemical doublelayer capacitors (EDLCs) for its high performance and low price [2]. Up to now, various porous carbon materials with different structures and morphologies have been fabricated for highperformance EDLCs [3]. The results suggested that high conductivity was as important a porous structure with large specific area for the electrodes of EDLCs [4]. The carbon structure with large specific area but low conductivity could not provide high capacitance at large current densities, in another word, its rate performance and power densities were largely limited. Designing porous carbon nanostructures with both large specific area and high conductivity was a key issue for the development of highperformance EDLCs. Recently, carbon nanotube and graphene were investigated as the porous electrodes of energy storage
n
Corresponding author. Tel./fax: þ 86 512 62872806. E-mail address: [email protected] (M. Chen).
http://dx.doi.org/10.1016/j.matlet.2015.01.020 0167-577X/& 2015 Elsevier B.V. All rights reserved.
devices such as EDLCs [5,6] and lithium batteries [7], for their superior conductivity to commercialized porous active carbon. However, their high price largely limited their applications in EDLCs. Electrospinning strategy was widely used to prepare polymer nanofiber non-woven nanotextiles. The chemical composition and diameter of these nanofibers could be easily controlled by tuning the precursor liquids and the electrospinning process parameters. Recently, these polymer nanofiber mats were used as the precursors to prepare carbon nanofiber (CNF) mat by carbonization process [8]. Porous CNF nanotextiles could be derived by introducing pore-makes into the liquid precursors of polymer for electrospinning. Inorganic metallic compounds such as ZnCl2 could largely increase the specific area of the as-prepared porous CNF nanotextiles to more than 500 cm2/g, which could induce large electrochemical double-layer capacitance [9]. However, the rate performance of the nanotextile was still limited without other conductive fillers. The liquid precursors of electrospinning could be coated onto CNT mat to form a CNT@porous carbon core-shell structural nanowire mat with the aim of enhancing the conductivity of porous carbon [10]. The rate performance of the composite mat could be effectively improved, but the practical specific capacitance was low for the small content of porous carbon in the composites. Highly conductive carbon nanomaterials such as multi-walled CNTs (MWCNTs) and graphene could be embedded
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L. Cheng et al. / Materials Letters 144 (2015) 123–126
into porous CNFs from electrospinning process for the applications of supercapacitors [11–13] and lithium batteries [14], thus the conductivity of the as-prepared porous CNF nanotextiles could be enhanced. However, the introduction of large-diameter MWCNTs into the CNF could induce the destruction of fiber shape, and graphene may decrease the practical specific area of the porous CNF mat by closing the pores in porous CNFs. In this research, single-walled CNTs were introduced into porous CNFs by dispersing SWCNTs into the liquid precursors of electrospinning. The composite nanotextile shows superior electrochemical performance to porous CNF, which makes it be a promising candidate for the electrodes of supercapacitors.
2. Experimental Single-walled carbon nanotubes (SWCNTs) were prepared by chemical vapor deposition (CVD) method [15] and purified by hydrochloric acid solution (2 M). The SWCNT had a purity of more than 90% with the Fe catalyst residual fewer than 10%, and its
specific was 400 m2/g. Polyacrylonitrile (PAN, MW ¼230,000) was purchased from Goodfollow Company Inc. Zinc acetate (Zn (CH2COO)2 2H2O), HCl (38%), potassium hydroxide (KOH) and N, N-dimethylformamide (DMF) were purchased from Sinopharm Chemical Reagent Co., Ltd. All reagents were directly used as received without further purification. The porous CNF/SWCNT nanotextiles were prepared through an electrospinning-carbonization procedure. Typically, 0.78 g of PAN was dissolved into 3 mL of DMF until the solution became transparent through stirring at 75 1C. 1.95 g of Zn(AC)2 2H2O was dissolved in 2 mL of DMF; and 0.03 g of SWCNT was dispersed in 5 mL of DMF by probe ultrasonication. The three solutions were mixed together with stirring for 3 h. The obtained homogeneous solution was used for electrospinning with a home-made setup. The electrospun fiber web was stabilized in air at 280 1C for 1.5 h and then carbonized at 800 1C for 2 h in argon. Finally, the obtained CNF nanotextile was soaked into nitric acid solution (1 M) for 1.5 h to remove the residual zinc oxide, and then CNFs became porous with large specific surface area. In order to illustrate the role of SWCNT in composite nanofiber, two samples, which are conventional non-porous CNF and porous
Fig. 1. SEM images of CNF (a, b), porous CNF (c, d) and porous CNF/SWCNT (e, f).
L. Cheng et al. / Materials Letters 144 (2015) 123–126
CNF without SWCNT, were synthesized with the same electrospinning and carbonization process. The surface morphologies of different products were observed by scanning electron microscope (SEM, HITACHI, S-4800, Japan). The specific surface areas and pore size distributions of the samples were evaluated using BET analysis (ASAP 2020, Micromeritics, USA). Raman spectroscopy (LABRAM HR, Horriba-JY, Japan) was used to determine the carbon structures. Conductivity test was carried out by a four-probe tester (ST-2258A, Jingge Electronic Co. Ltd., China). The electrochemical performance of the porous CNF/SWCNT composite nanotextile was tested by a CHI660C electrochemical workstation. A three-electrode system was used to evaluate the electrochemical performance, in which Pt foil (1 2 cm2) was the counter electrode and saturated calomel electrode was the reference electrode. 6 M KOH aqueous solution was used as the electrolyte.
3. Results and discussion The SEM images of CNF, porous CNF and porous CNF/SWCNT were shown in Fig. 1. Compared with other samples, CNF shows a finer diameter (Fig. 1a) with smoother surface (Fig. 1b), suggesting that pure PAN solution has excellent electrospinning performance. With the addition of Zn(AC)2 as pore maker, porous CNF shows uneven diameter size with rough surface, which could largely increase the specific surface area. The image of its fracture section shows many pore pipes along the surface and radial direction, which were resulted from the removing the ZnO. These pipes formed by removing ZnO indicated that the introduction of SWCNTs may change the distribution of ZnO in these CNFs. BET test shows that pristine non-porous CNF has the lowest specific surface area (10.97 m2/g), while porous CNF/SWCNT shows the highest specific surface area (132.70 m2/g), higher than porous CNF without SWCNTs (118.73 m2/g). It could largely increase the electrochemical double-layer capacitance. Although the specific areas of the samples are not as high as pure SWCNT films, the surface chemical inert and metallic catalyst residual of the latter limited their practical performance [16]. Fig. 2 shows the Raman spectra of CNF, porous CNF, porous CNF/ SWCNT and pristine SWCNTs, respectively. Fig. 2a shows significant G-band (1590 cm 1) and D-band (1360 cm 1) for the three samples, indicating their effective carbonization. Furthermore, the RBM peaks between 100 and 300 cm 1 existed in porous CNF/SWCNT samples. They are also existed in the Raman spectrum of pristine SWCNTs, which means the effective composition of SWCNTs into the porous CNFs. These SWCNTs could largely increase the conductivity of porous CNFs. Table 1 shows the conductivity comparison of the three samples, which suggests CNF/SWCNT composite has much higher conductivity (8.92 S/m) than pristine porous CNF (2.68 S/m). It could be beneficial for enhancing the electrochemical rate performance of the composite nanotextiles. Cyclic voltammetry (CV), charge/discharge and cycle life tests were carried out to investigate the electrochemical performance of the samples. Fig. 3a shows CV curves of different samples (CNF, porous CNF, and lamellar porous CNF/SWCNT) at a scan rate of 5 mV/s. It can be seen that all the three samples show the typical square shaped CV curves, which indicate ideal electrochemical double-layer capacitive behaviors. The larger cycle area of CV indicates the higher specific capacitance. Among the three samples, porous CNF/SWCNT nanotextile shows not only the most ideal square-shaped CV curve but also the highest peak current density and the largest cycle area, indicating the superior capacitive performances. Fig. 3b shows the charge/discharge curves at the current density of 1 A/g, and the symmetrical triangle curves indicate the good reversibility of electrodes. The specific
125
capacitance of the electrode was calculated from discharge curve. Fig. 3c show the calculated rate performance comparison of the three samples, which indicates the introduction of SWCNTs into porous CNF can dramatically increase both the practical specific capacitance and the rate performance. The specific capacitance of the porous nanotextile could achieve 417 F/g at current density of 0.5 A/g and keep 193 F/g at high current density of 10 A/g. Furthermore, its specific capacitance could keep 96% after 2000 cycles of charge/discharge at 10 A/g (see Fig. 3d). Thus this nanotextile could serve as the electrodes of high-performance electrochemical double-layer supercapacitors.
4. Conclusions In summary, SWCNTs could be uniformly composted with polymer nanofibers in electrospinning process. The porous CNF/ SWCNT nanotextile was achieved after carbonization and ZnO pore-maker removing. The composite nanotextile shows higher practical specific capacitance and better rate performance than the pure porous CNF nanotextile for the enhancement of electrical conductivity. Its specific capacitance can achieve 417 F/g at the current density of 0.5 A/g, and keep 193 F/g at the current density Table 1 Conductivity for different carbon nano-fibers. Samples
CNF
Porous CNF
Lamellar porous CNF/SWCNT
Conductivity (S/m)
36.80
2.68
8.92
Fig. 2. Raman spectra: (a) different CNFs and (b) SWCNTs.
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Fig. 3. Electrochemical performance: (a) CV curves at 5 mV/s; (b) charge/discharge curves at the current density of 1 A/g; (c) rate performance comparison; (d) cyclic lifetime curve of lamellar porous CNF/SWCNT at current density of 10 A/g.
of 10 A/g. Furthermore, this composite nanotextile shows excellent cyclic performance at large current densities. Thus it could be expected to be a highly promising candidate for application in high-performance electrochemical double-layer supercapacitors. Acknowledgements The project was supported by the National Science Foundation of China (no. 21203238). References [1] Simon P, Gogotsi Y. Nat Mater 2018;7:845–854. [2] Dutta S, Bhaumik A, Wu KCW. Energy Environ Sci 2014;7:3574–92. [3] Beguin F, Presser V, Balducci A, Frackowiak E. Adv Mater 2014;26:2219–51.
[4] Geng Y, Song Y, Zhong M, Shi J, Guo Q, Liu L. Mater Lett 2010;64:2673–5. [5] Niu Z, Dong H, Zhu B, Li J, Hng HH, Zhou W, Chen X, Xie S. Adv Mater 2013;25:1058–64. [6] Chen Y, Zhang X, Zhang D, Ma Y. Mater Lett 2012;68:475–7. [7] Peng HJ, Huang JQ, Zhao MQ, Zhang Q, Cheng XB, Liu XY, Qian WZ, Wei F. Adv Funct Mater 2014;24:2772–81. [8] Inagaki M, Yang Y, Kang F. Adv Mater 2012;24:2547–66. [9] Kim C, Ngoc BTN, Yang KS, Kojima M, Kim YA, Kim YJ, Endo M, Yang SC. Adv Mater 2007;19:2341–6. [10] Chen H, Di J, Jin Y, Chen M, Tian J, Li Q. J Power Sources 2013;237:325–31. [11] Guo Q, Zhou X, Li X, Chen S, Seema A, Greiner A, Hou H. J Mater Chem 2009;19:2810–6. [12] Zhou Z, Wu XF, Fong H. Appl Phys Lett 2012;100:023115. [13] Dong Q, Wang G, Hu H, Yang J, Qian B, Ling Z, Qiu J. J Power Source 2013;243:350–3. [14] Zeng L, Pan F, Li W, Jiang Y, Zhong X, Yu Y. Nanoscale 2014;6:9579–87. [15] Li Q, Yan H, Cheng Y, Zhang J, Liu Z. J Mater Chem 2002;12:1179–83. [16] Niu Z, Zhou W, Chen J, Feng G, Li H, Ma W, Li J, Dong H, Ren Y, Zhao D, Xie S. Energy Environ Sci 2011;4:1440–6.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Single-walled carbon nanotube embedded porous carbon nanofiber with enhanced electrochemical capacitive performance Lin Cheng a,c, Junjia He a, Yu Jin b, Hongyuan Chen b, Minghai Chen b,n a
College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074, China Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, China c State Grid Electric Power Research Institute, Luoyu Road 143, Wuhan 430074, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 4 November 2014 Accepted 7 January 2015 Available online 15 January 2015
Active carbon nanofibers (CNFs) with porous structure show highly electrochemical double-layer capacitance for supercapacitors because of their large specific area. However, their poor crystallization induced the low conductivity, which could largely limit the electrochemical performance of the porous CNFs. In this research, porous CNFs with single-walled carbon nanotubes (SWCNTs) were prepared by electrospinning and high temperature carbonization. The introduction of SWCNTs into porous CNFs could largely enhance the conductivity of the porous CNF nanotextiles, thus the electrochemical performance of the composite nanotextile was largely enhanced. The specific capacitance of the composite could achieve 417 F/g at a current density of 0.5 A/g, and keep 193 F/g at the high current density of 10 A/g. Furthermore its specific capacitance could keep 96% after 2000 cycles of charge/ discharge at the current density of 10 A/g. This nanotextile could be a promising candidate for the binder-free and filler-free electrodes of high-performance supercapacitors. & 2015 Elsevier B.V. All rights reserved.
Keywords: Electrospinning Carbon nanotube Porous carbon nanofiber Energy storage and conversion
1. Introduction Supercapacitors (also called electrochemical capacitors (ECs)) could provide higher power and longer cyclic lifetime than batteries, thus could be widely used in numerous applications such as power sources in electrical vehicles and portable electronic devices [1]. Porous carbon with large specific area plays an important role as the electrodes of the electrochemical doublelayer capacitors (EDLCs) for its high performance and low price [2]. Up to now, various porous carbon materials with different structures and morphologies have been fabricated for highperformance EDLCs [3]. The results suggested that high conductivity was as important a porous structure with large specific area for the electrodes of EDLCs [4]. The carbon structure with large specific area but low conductivity could not provide high capacitance at large current densities, in another word, its rate performance and power densities were largely limited. Designing porous carbon nanostructures with both large specific area and high conductivity was a key issue for the development of highperformance EDLCs. Recently, carbon nanotube and graphene were investigated as the porous electrodes of energy storage
n
Corresponding author. Tel./fax: þ 86 512 62872806. E-mail address: [email protected] (M. Chen).
http://dx.doi.org/10.1016/j.matlet.2015.01.020 0167-577X/& 2015 Elsevier B.V. All rights reserved.
devices such as EDLCs [5,6] and lithium batteries [7], for their superior conductivity to commercialized porous active carbon. However, their high price largely limited their applications in EDLCs. Electrospinning strategy was widely used to prepare polymer nanofiber non-woven nanotextiles. The chemical composition and diameter of these nanofibers could be easily controlled by tuning the precursor liquids and the electrospinning process parameters. Recently, these polymer nanofiber mats were used as the precursors to prepare carbon nanofiber (CNF) mat by carbonization process [8]. Porous CNF nanotextiles could be derived by introducing pore-makes into the liquid precursors of polymer for electrospinning. Inorganic metallic compounds such as ZnCl2 could largely increase the specific area of the as-prepared porous CNF nanotextiles to more than 500 cm2/g, which could induce large electrochemical double-layer capacitance [9]. However, the rate performance of the nanotextile was still limited without other conductive fillers. The liquid precursors of electrospinning could be coated onto CNT mat to form a CNT@porous carbon core-shell structural nanowire mat with the aim of enhancing the conductivity of porous carbon [10]. The rate performance of the composite mat could be effectively improved, but the practical specific capacitance was low for the small content of porous carbon in the composites. Highly conductive carbon nanomaterials such as multi-walled CNTs (MWCNTs) and graphene could be embedded
124
L. Cheng et al. / Materials Letters 144 (2015) 123–126
into porous CNFs from electrospinning process for the applications of supercapacitors [11–13] and lithium batteries [14], thus the conductivity of the as-prepared porous CNF nanotextiles could be enhanced. However, the introduction of large-diameter MWCNTs into the CNF could induce the destruction of fiber shape, and graphene may decrease the practical specific area of the porous CNF mat by closing the pores in porous CNFs. In this research, single-walled CNTs were introduced into porous CNFs by dispersing SWCNTs into the liquid precursors of electrospinning. The composite nanotextile shows superior electrochemical performance to porous CNF, which makes it be a promising candidate for the electrodes of supercapacitors.
2. Experimental Single-walled carbon nanotubes (SWCNTs) were prepared by chemical vapor deposition (CVD) method [15] and purified by hydrochloric acid solution (2 M). The SWCNT had a purity of more than 90% with the Fe catalyst residual fewer than 10%, and its
specific was 400 m2/g. Polyacrylonitrile (PAN, MW ¼230,000) was purchased from Goodfollow Company Inc. Zinc acetate (Zn (CH2COO)2 2H2O), HCl (38%), potassium hydroxide (KOH) and N, N-dimethylformamide (DMF) were purchased from Sinopharm Chemical Reagent Co., Ltd. All reagents were directly used as received without further purification. The porous CNF/SWCNT nanotextiles were prepared through an electrospinning-carbonization procedure. Typically, 0.78 g of PAN was dissolved into 3 mL of DMF until the solution became transparent through stirring at 75 1C. 1.95 g of Zn(AC)2 2H2O was dissolved in 2 mL of DMF; and 0.03 g of SWCNT was dispersed in 5 mL of DMF by probe ultrasonication. The three solutions were mixed together with stirring for 3 h. The obtained homogeneous solution was used for electrospinning with a home-made setup. The electrospun fiber web was stabilized in air at 280 1C for 1.5 h and then carbonized at 800 1C for 2 h in argon. Finally, the obtained CNF nanotextile was soaked into nitric acid solution (1 M) for 1.5 h to remove the residual zinc oxide, and then CNFs became porous with large specific surface area. In order to illustrate the role of SWCNT in composite nanofiber, two samples, which are conventional non-porous CNF and porous
Fig. 1. SEM images of CNF (a, b), porous CNF (c, d) and porous CNF/SWCNT (e, f).
L. Cheng et al. / Materials Letters 144 (2015) 123–126
CNF without SWCNT, were synthesized with the same electrospinning and carbonization process. The surface morphologies of different products were observed by scanning electron microscope (SEM, HITACHI, S-4800, Japan). The specific surface areas and pore size distributions of the samples were evaluated using BET analysis (ASAP 2020, Micromeritics, USA). Raman spectroscopy (LABRAM HR, Horriba-JY, Japan) was used to determine the carbon structures. Conductivity test was carried out by a four-probe tester (ST-2258A, Jingge Electronic Co. Ltd., China). The electrochemical performance of the porous CNF/SWCNT composite nanotextile was tested by a CHI660C electrochemical workstation. A three-electrode system was used to evaluate the electrochemical performance, in which Pt foil (1 2 cm2) was the counter electrode and saturated calomel electrode was the reference electrode. 6 M KOH aqueous solution was used as the electrolyte.
3. Results and discussion The SEM images of CNF, porous CNF and porous CNF/SWCNT were shown in Fig. 1. Compared with other samples, CNF shows a finer diameter (Fig. 1a) with smoother surface (Fig. 1b), suggesting that pure PAN solution has excellent electrospinning performance. With the addition of Zn(AC)2 as pore maker, porous CNF shows uneven diameter size with rough surface, which could largely increase the specific surface area. The image of its fracture section shows many pore pipes along the surface and radial direction, which were resulted from the removing the ZnO. These pipes formed by removing ZnO indicated that the introduction of SWCNTs may change the distribution of ZnO in these CNFs. BET test shows that pristine non-porous CNF has the lowest specific surface area (10.97 m2/g), while porous CNF/SWCNT shows the highest specific surface area (132.70 m2/g), higher than porous CNF without SWCNTs (118.73 m2/g). It could largely increase the electrochemical double-layer capacitance. Although the specific areas of the samples are not as high as pure SWCNT films, the surface chemical inert and metallic catalyst residual of the latter limited their practical performance [16]. Fig. 2 shows the Raman spectra of CNF, porous CNF, porous CNF/ SWCNT and pristine SWCNTs, respectively. Fig. 2a shows significant G-band (1590 cm 1) and D-band (1360 cm 1) for the three samples, indicating their effective carbonization. Furthermore, the RBM peaks between 100 and 300 cm 1 existed in porous CNF/SWCNT samples. They are also existed in the Raman spectrum of pristine SWCNTs, which means the effective composition of SWCNTs into the porous CNFs. These SWCNTs could largely increase the conductivity of porous CNFs. Table 1 shows the conductivity comparison of the three samples, which suggests CNF/SWCNT composite has much higher conductivity (8.92 S/m) than pristine porous CNF (2.68 S/m). It could be beneficial for enhancing the electrochemical rate performance of the composite nanotextiles. Cyclic voltammetry (CV), charge/discharge and cycle life tests were carried out to investigate the electrochemical performance of the samples. Fig. 3a shows CV curves of different samples (CNF, porous CNF, and lamellar porous CNF/SWCNT) at a scan rate of 5 mV/s. It can be seen that all the three samples show the typical square shaped CV curves, which indicate ideal electrochemical double-layer capacitive behaviors. The larger cycle area of CV indicates the higher specific capacitance. Among the three samples, porous CNF/SWCNT nanotextile shows not only the most ideal square-shaped CV curve but also the highest peak current density and the largest cycle area, indicating the superior capacitive performances. Fig. 3b shows the charge/discharge curves at the current density of 1 A/g, and the symmetrical triangle curves indicate the good reversibility of electrodes. The specific
125
capacitance of the electrode was calculated from discharge curve. Fig. 3c show the calculated rate performance comparison of the three samples, which indicates the introduction of SWCNTs into porous CNF can dramatically increase both the practical specific capacitance and the rate performance. The specific capacitance of the porous nanotextile could achieve 417 F/g at current density of 0.5 A/g and keep 193 F/g at high current density of 10 A/g. Furthermore, its specific capacitance could keep 96% after 2000 cycles of charge/discharge at 10 A/g (see Fig. 3d). Thus this nanotextile could serve as the electrodes of high-performance electrochemical double-layer supercapacitors.
4. Conclusions In summary, SWCNTs could be uniformly composted with polymer nanofibers in electrospinning process. The porous CNF/ SWCNT nanotextile was achieved after carbonization and ZnO pore-maker removing. The composite nanotextile shows higher practical specific capacitance and better rate performance than the pure porous CNF nanotextile for the enhancement of electrical conductivity. Its specific capacitance can achieve 417 F/g at the current density of 0.5 A/g, and keep 193 F/g at the current density Table 1 Conductivity for different carbon nano-fibers. Samples
CNF
Porous CNF
Lamellar porous CNF/SWCNT
Conductivity (S/m)
36.80
2.68
8.92
Fig. 2. Raman spectra: (a) different CNFs and (b) SWCNTs.
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L. Cheng et al. / Materials Letters 144 (2015) 123–126
Fig. 3. Electrochemical performance: (a) CV curves at 5 mV/s; (b) charge/discharge curves at the current density of 1 A/g; (c) rate performance comparison; (d) cyclic lifetime curve of lamellar porous CNF/SWCNT at current density of 10 A/g.
of 10 A/g. Furthermore, this composite nanotextile shows excellent cyclic performance at large current densities. Thus it could be expected to be a highly promising candidate for application in high-performance electrochemical double-layer supercapacitors. Acknowledgements The project was supported by the National Science Foundation of China (no. 21203238). References [1] Simon P, Gogotsi Y. Nat Mater 2018;7:845–854. [2] Dutta S, Bhaumik A, Wu KCW. Energy Environ Sci 2014;7:3574–92. [3] Beguin F, Presser V, Balducci A, Frackowiak E. Adv Mater 2014;26:2219–51.
[4] Geng Y, Song Y, Zhong M, Shi J, Guo Q, Liu L. Mater Lett 2010;64:2673–5. [5] Niu Z, Dong H, Zhu B, Li J, Hng HH, Zhou W, Chen X, Xie S. Adv Mater 2013;25:1058–64. [6] Chen Y, Zhang X, Zhang D, Ma Y. Mater Lett 2012;68:475–7. [7] Peng HJ, Huang JQ, Zhao MQ, Zhang Q, Cheng XB, Liu XY, Qian WZ, Wei F. Adv Funct Mater 2014;24:2772–81. [8] Inagaki M, Yang Y, Kang F. Adv Mater 2012;24:2547–66. [9] Kim C, Ngoc BTN, Yang KS, Kojima M, Kim YA, Kim YJ, Endo M, Yang SC. Adv Mater 2007;19:2341–6. [10] Chen H, Di J, Jin Y, Chen M, Tian J, Li Q. J Power Sources 2013;237:325–31. [11] Guo Q, Zhou X, Li X, Chen S, Seema A, Greiner A, Hou H. J Mater Chem 2009;19:2810–6. [12] Zhou Z, Wu XF, Fong H. Appl Phys Lett 2012;100:023115. [13] Dong Q, Wang G, Hu H, Yang J, Qian B, Ling Z, Qiu J. J Power Source 2013;243:350–3. [14] Zeng L, Pan F, Li W, Jiang Y, Zhong X, Yu Y. Nanoscale 2014;6:9579–87. [15] Li Q, Yan H, Cheng Y, Zhang J, Liu Z. J Mater Chem 2002;12:1179–83. [16] Niu Z, Zhou W, Chen J, Feng G, Li H, Ma W, Li J, Dong H, Ren Y, Zhao D, Xie S. Energy Environ Sci 2011;4:1440–6.