- Email: [email protected]
polyaniline inks
Accepted Manuscript Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline Inks Yanfei Xu, Ingolf Hennig, Dieter Freyberg, Andrew James Strudwick, Matthias Georg Schwab, Thomas Weitz, Kitty Chih-Pei Cha PII:
S0378-7753(13)01602-9
DOI:
10.1016/j.jpowsour.2013.09.096
Reference:
POWER 18058
To appear in:
Journal of Power Sources
Received Date: 25 May 2013 Revised Date:
14 September 2013
Accepted Date: 24 September 2013
Please cite this article as: Y. Xu , I. Hennig, D. Freyberg, A. James Strudwick, M. Georg Schwab, T. Weitz, K. Chih-Pei Cha, Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline Inks, Journal of Power Sources (2013), doi: 10.1016/j.jpowsour.2013.09.096. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Highlights (POWER 18058) (1) Graphene/polyaniline (NGP/PANI) inks have been formulated successfully.
RI PT
(2) NGP/PANI electrodes are produced by inkjet-printed technology. (3) Two-electrode supercapacitors are fabricated using NGP/PANI electrodes.
(4) Supercapacitors show high electrochemical performance and a long cycle life.
AC C
EP
TE D
M AN U
SC
(5) The above results show a promising field of printed supercapacitors.
ACCEPTED MANUSCRIPT
Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline Inks Yanfei Xu1*, Ingolf Hennig2, Dieter Freyberg3, Andrew James Strudwick1, Matthias Georg Schwab1, Thomas Weitz3, Kitty Chih-Pei Cha1
RI PT
Dr. Y. Xu, Dr. A. Strudwick, Dr. M. Schwab, Dr. K. Cha, Carbon Materials Innovation Center, GVM/I, BASF SE, 67056 Ludwigshafen, Germany Dr. I. Hennig, GMC/R, BASF SE, 67056 Ludwigshafen, Germany
D. Freyberg, Dr. T. Weitz, GVE/F, BASF SE, 67056 Ludwigshafen, Germany
SC
*Corresponding author Tel/ fax: +49 621 6095198 [email protected]
Abstract: In this work, graphene/polyaniline (NGP/PANI) inks are formulated; inkjet printing
M AN U
technology is then used to produce NGP/PANI thin-film electrodes from these inks. With this inkjet printing, good control over a number of key film properties including pattern geometry, pattern location, film thickness, and electrical conductivity is achieved. Two-electrode supercapacitors are fabricated using these thin-film electrodes. Electrochemical measurements with a 1M H2SO4 electrolyte yield a maximum specific capacitance of 82 F g-1, power density of
TE D
124 kW kg-1 and energy density of 2.4 Wh kg-1 when a scan rate of 20 mV s-1 is applied. The supercapacitors show a long cycle life over 1000 cycles. Keyword: graphene/polyaniline ink, inkjet printing, thin-film electrode, supercapacitor, industrial
1. Introduction
EP
applicability.
Continuing advances in the miniaturization of electronic devices has resulted in an increased
AC C
demand for rechargeable power sources that can be rapidly charged and have a long cycle life [1]. To provide peak power, conventional charge storage devices, such as batteries, need to be bulky and heavy, and are not suitable for use in the next generation of portable electronic devices, which are required to be lightweight, ultrathin, and fully flexible [2,3]. As a consequence, lightweight supercapacitors with the advantages of high power density, high energy density and long cycle life are considered to be one of the most promising energy storage devices to satisfy future energy storage needs.
1
ACCEPTED MANUSCRIPT
Printable energy storage devices are of great interest for industrial applications in terms of commercially viable energy storage products and can be produced on a large scale via solution based roll-to-roll methods [4]. Recent successful alternative methods include a spray method to produce SWNT thin film electrodes for supercapacitors [5], and use of the Meyer rod coating
RI PT
method to spread carbon nanotubes on paper for use in both supercapacitors and lithium ion batteries [6]. However, the above mentioned methods typically produce continuous films with no control over geometry and position. Inkjet printing provides the capability of printing films in
SC
controlled geometries and at specific locations on various substrates as it is a direct write process. Inkjet printing methods have been used as one of the key technologies in the fields of organic transistors [7], light-emitting devices [8], solar cells [9], and sensors [10]. To date there have been
addresses this key application.
M AN U
few reports on the production of energy storage devices via inkjet printing [4], the present work
Since the performance of inkjet-printable supercapacitor electrode is strongly governed by the ink that is applied during the process, it is therefore necessary to investigate which materials are best suited for the functional ink formulation. The large surface area and high electrical
TE D
conductivity of graphene makes this versatile carbon material promising for the ink formulation and practical electric double-layer capacitor (EDLC) applications [11-14]. Recent work by several groups produced curved nano graphene platelets (NGP) by oxidation of graphite according to a modified Hummers’ method followed by a subsequent thermal shock exposure exfoliation method
EP
[15-19]. The specific capacitances of these NGP based supercapacitors in an ionic liquid electrolyte are 100-250 F g-1, with an energy density of 85.6 Wh kg-1. This shows a great
AC C
improvement on the previous best result of 28.5 Wh kg-1 obtained elsewhere using graphene materials produced via the hydrazine reduction of graphene oxide [20]. Conducting polymers are another promising electrode material for supercapacitors due to their
high pseudocapacitance [21]. The pseudocapacitance originates from the conducting polymer undergoing fast and reversible faradic redox reactions. As a typical conducting polymer, polyaniline (PANI) has long been a very favorable material for supercapacitor electrode due to its ease of synthesis, processability, and special redox activity [21,22]. However, one of the drawbacks for PANI as supercapacitor electrode is its poor cycling stability because PANI is 2
ACCEPTED MANUSCRIPT
usually brittle and weak in mechanical strength. Additionally, PANI exhibits only moderate electrical conductivity. Graphene has been used as an excellent substrate to host active polymer nanomaterial [23], to overcome these drawbacks of PANI, NGP can also serve as a stable and underlying conductive
RI PT
network for the PANI when combining the NGP and PANI together [22,24]. As such, high capacitance and improved stability is expected to be achieved with NGP/PANI hybrid materials. It
is attractive to formulate NGP/PANI inks to harness these excellent synergistic capacitive
SC
properties.
Here, we formulate NGP/PANI inks and demonstrate the fabrication of supercapacitor electrodes via inkjet printing of these inks. The electrochemical properties of the supercapacitors
impedance spectroscopy techniques. 2. Experimental section 2.1 NGP ink production
M AN U
are investigated by means of cyclic voltammetry (CV), galvanostatic charge discharge and
For the NGP ink production, NGP powder (200 mg), SDBS surfactant (200 mg) and H2O (100
TE D
mL) are added to a glass bottle. The mixture is then probe ultrasonicated for 1 hour (400 watts, 24 kHz), at 10 oC. After this process, the above solution is centrifugated at 500 rpm for 10 minutes; the supernatant is collected and used as the NGP ink. 2.2 NGP/PANI ink production
EP
In a similar process to above the NGP inks are formulated by, NGP powder (200 mg), SDBS surfactant (200 mg) and H2O (100 mL) are added to a glass bottle. The mixture is then probe
AC C
ultrasonicated for 1 hour (400 watts, 24 kHz), at 10 oC. After this process, PANI (200 mg) is added to the above mixture, and probe ultrasonicated for 30 minutes (400 watts, 24 kHz), at 10 oC. Finally, the above solution is centrifugated at 500 rpm for 10 minutes; the supernatant is collected and used as NGP/PANI ink. 2.3 Inkjet printing experiment Inkjet printing experiment is performed at room temperature, the printing parameters are as follows: A voltage of 86 V is used along with a pulse length of 40 µs, the strobe delay is 400 µs, at a frequency of 500 Hz, and a pressure of -5 mbar. The printing is carried out with a grid size of 3
ACCEPTED MANUSCRIPT
800 points, and a grid distance of 0.013 mm. After the printing process, the samples are dried for 2 hours at 80 oC. The weight of the NGP/PANI electrode materials (1.5 mg/cm2) is calculated from the difference in weight between the substrate weight before printing and the substrate weight after printing.
RI PT
3. Results and discussion
The presence of oxygen-containing groups in NGP renders it strongly hydrophilic and water
soluble [25]. Results of atomic force microscopy (AFM, Supporting Information, Figure S1) have
SC
confirmed that NGP can be easily “unfolded” by applying liquid-assisted exfoliation procedures [25,26]. Transmission electron microscopy (TEM) characterization also confirm that NGP and NGP/PANI materials can be dispersed homogenously in water and consist of very thin exfoliated
M AN U
sheets as indicated by their high translucency to the electrons used in TEM analysis shown in
TE D
Figure 1A and 1B.
Figure 1. (A) TEM image of NGP. (B) TEM image of NGP/PANI. TEM results confirm that
EP
NGP, NGP/PANI material can be dispersed homogenously in water, which consists of single and few-layers crumpled NGP sheets.
AC C
As the key property of inks viable for inkjet printing is their ability to generate droplets, it is
very important to prevent nozzle clogging during the inkjet printing. Therefore, the quality of ink depends highly on the NGP/PANI particle size, the ink surface tension and especially the viscosity of the ink. From AFM analysis it can be seen that a wrinkle-like structure exists in the NGP and that the platelets have a typical thickness of 5-10 nm (Figure S1A). And analysis of a large number of NGP/PANI images revealed that most of the continuous sheets have lateral dimensions of hundreds of nanometers with heights in the range 40-80 nm, as shown in Figure S1B. The surface tension values for the NGP and NGP/PANI inks are 34 and 36 mN m-1 respectively. The 4
ACCEPTED MANUSCRIPT
NGP and NGP/PANI inks used herein show a viscosity of around 1 mPa•s observed at a shearing rate of 300-3000 s-1 (Figure S2). From the surface tension and viscosity results we conclude that the ink formulation used in this work fits the inkjet-printing requirements [27]. Next, we turn to the description of the inkjet printing process that is applied in this study. The
RI PT
inkjet printing process involves the ejection of a fixed quantity of ink from a chamber, via a nozzle
due to a sudden, quasi-adiabatic reduction of the chamber volume via piezoelectric action (Figure
S3). The chamber, filled with liquid, is contracted in response to application of an external voltage.
SC
This sudden reduction causes a shockwave in the liquid, which leads to the ejection of a liquid
drop from the nozzle. The ejected drop falls until it impinges on the substrate, spreads under
then dries through solvent evaporation [28].
M AN U
momentum acquired in the motion, and surface tension aided flow along the surface. The drop
A common challenge with inkjet printing is the inability to produce thin and homogeneous films. Here we show that these problems can be avoided with electrically conductive NPG and NGP/PANI films obtained on quartz substrates merely through multiple prints over the same pattern. The NGP/PANI thin film is printed on the quartz substrate, and the conductivity for the
TE D
NGP thin film (5 prints, thickness ~41µm) is 3.67 S/cm (99 Ohm/sq), while the conductivity for the NGP/PANI thin film (5 prints, thickness ~28 µm) is 0.29 S/cm (846 Ohm/sq), while the pure PANI conductivity is only 10-9 S/cm [29].
In addition, homogeneous NGP/PANI thin films can be easily printed on the carbon fabric
EP
substrate, with good control over pattern geometry and location (Figure S4). Compared with quartz substrates, conductive carbon fabric substrates dramatically improve film adhesion even
AC C
without binder, and simplify the coating process due to the fibrous paper-like structure of the material. Moreover, as the carbon fabric substrates are electrically conductive, NGP/PANI thin films printed on these substrates can be used as electrodes directly for supercapacitor devices. Raman spectroscopy (Figure 2) is used to study the surface compositions of the NGP and
NGP/PANI films. NGP shows two distinctive peaks centered at ~1363 cm-1 and ~1590 cm-1 that correspond to D and G bands, respectively [30]. Three new representative peaks arising from PANI can be indexed at 1184, 1234, 1508 cm-1, apart from the D/G bands of graphene. They correspond to the C-H bending vibration of benzenoid rings, C-N stretching vibration of 5
ACCEPTED MANUSCRIPT
benzenoid rings, and stretching vibrating of C=N in quinonoid ring systems of PANI [31]. PANI
SC
RI PT
is possibly adsorbed onto the surface of NGP by π-π stacking [32].
Figure 2. Raman spectrum of NGP and NGP/PANI thin films. A 20X optical objective is used to
M AN U
focus the laser spot which is filtered to 10% of its maximum power using a neutral density filter (leading to ~1 mW power on the sample surface). The exposure time used is 100 s. Figure 3 shows scanning electron microscope (SEM) images of the surface of NGP and NGP/PANI thin films that have been printed onto the carbon fabric substrates. The NGP formed homogeneous networks on the substrate surface, as shown in Figures 3A and 3C. Figures 3B and 3D show the cross section of the NGP and NGP/PANI thin films. NGP exhibits a layer structure
TE D
on the conductive substrate, keeping the advantage of the entangled network of the NGP that also
AC C
EP
promotes good access of the electrolyte to the active PANI material.
Figure 3. (A) SEM surface images of NGP thin film on carbon substrate. (B) SEM cross section images of the NGP thin films on the substrate. (C) SEM surface images of NGP/PANI thin film on carbon substrate. (D) SEM cross section images of the NGP/PANI thin films on the substrate. 6
ACCEPTED MANUSCRIPT
Nitrogen adsorption-desorption analysis is used to determine the specific surface area of the NGP and NGP/PANI thin films. The corresponding values are 69 m2 g-1 and 287 m2 g-1 respectively, while the specific surface area for pure PANI and blank carbon substrate is only 34 and 2 m2 g-1 respectively [20,33]. We suggest that the adsorption of PANI can serve as spacer to
RI PT
further separate NGP neighboring sheets, increases the specific surface area of NGP. This is favorable for increasing the EDLC of supercapacitors.
Using best-practice methods for determining an electrode material’s performance for
SC
supercapacitors, we constructed and measured the performance of two-electrode symmetrical
supercapacitor devices on the basis of NGP/PANI electrodes and H2SO4 electrolyte [13]. Two asprinted NGP/PANI electrodes on carbon fabric substrate are used as electrodes without any further
M AN U
treatment, and sandwiched together with a separator to form an electrochemical capacitor, using a 1M H2SO4 electrolyte, as shown in Figure 4A. The printed NGP/PANI films on carbon substrates used in the fabrication of supercapacitors are typically 5 prints. It should be noted that the two electrode supercapacitor test fixture configuration closely matches the performance of a packaged supercapacitor cell[34]. The NGP/PANI thin film is used as an active electrode, with the carbon
TE D
fabric substrate serving as a current collector (Supporting Information for the supercapacitor test cells setup details). The electrochemical behaviors of the resulting supercapacitors are investigated by CV methods. Figures 4B and 4C show the CV results of NGP and NGP/PANI electrodes obtained at different scan rates. The redox peaks of NGP/PANI films are attributed to the redox of
PANI,
corresponding
EP
transition
to
its
leucoemeraldine/emeraldine
and
emeraldine/pernigraniline structural conversions [25]. This observation additionally confirms the
AC C
presence of pseudocapacitive PANI in the electrodes. There is an increase in the current density at high scan rate; this demonstrates good conductivity
and capacitive behavior of the NGP and NGP/PANI electrodes [24]. The specific capacitance (Csp) is calculated based on the integrated area of the CV discharge curves yielding an average discharge current (Id). Csp = 2 C/m (C is the measured capacitance for the two-electrode cell C=Id/(dV/dt), and m is the average mass of one electrode, including the mass of SDBS surfactant). At a high scan rate of 20 mV s-1, the NGP/PANI supercapacitor delivers a specific capacitance of 70 F g-1 (Figure 4D), while the NGP based supercapacitor delivers a specific capacitance of 10 F 7
ACCEPTED MANUSCRIPT
g-1. These measurement results show the synergistic effect of NGP/PANI resulting from the
M AN U
SC
RI PT
pseudocapacitance of PANI and from the physical charge storage contribution of the NGP.
Figure 4 (A) Supercapacitor device structure. (B) CV curves of NGP electrodes measured at
TE D
different scan rates, in 1M H2SO4 electrolyte, two-electrode system. (C) CV curves of NGP/PANI electrodes measured at different scan rates, in 1M H2SO4 electrolyte, two-electrode system. (D) Specific capacitance as a function of scan rate in two electrode system, with 1M H2SO4 aqueous
EP
electrolyte.
In Figure 5A, the Nyquist plot of supercapacitors with NGP/PANI electrodes show a straight
AC C
line in the low-frequency region and an unconspicuous arc in the high frequency region. These plots do not show semicircle regions, probably due to the low faradaic resistances of the NGP/PANI electrode [24]. The high frequency part of NGP/PANI shows a Warburg type impedance behavior and is related to the diffusion of ions within the porous structure.[20]. The vertical shape at lower frequencies indicates a purely capacitive behavior; the more vertical the curve, the more closely the supercapacitor behaves as an ideal capacitor. The equivalent series resistance (ESR), as estimated from the intercept of the curve on the x-axis, is about 0.28 Ω (Figure 5A inset). The ESR measurement can be used to estimate the rate at which the 8
ACCEPTED MANUSCRIPT
supercapacitor can be charged-discharged, and it is an important factor in determining the power density of the device. Consequently, the maximum power density of the supercapacitor has been calculated according to the equation Pmax=Vmax2/4MR, where Vmax is the maximum voltage, R is the ESR and M is the mass of the two electrodes [20]. The energy density E is given by:
RI PT
E=CVmax2/2M. With a cell voltage of 1.0 V, the NGP/PANI supercapacitor exhibits a high power density of 124 kW kg-1, with an energy density of 2.4 Wh kg-1 at a scan rate of 20 mV s-1 (this
value was calculated based on the active material including SDBS surfactant.). In comparison, the NGP supercapacitor exhibits power density of 132 kW kg-1, with an energy density of 0.3 Wh kg-1
AC C
EP
TE D
M AN U
SC
at a scan rate of 20 mV s-1.
Figure 5 (A) Nyquist plots of NGP and NGP/PANI supercapacitor device. (B) Cycling stability of the supercapacitor device over 1000 cycles, cycling stability measured at a constant current density of 1.4 A/g, with 1M H2SO4 electrolyte. To further confirm the merits of the NGP/PANI thin films as supercapacitor electrodes, a typical galvanostatic charge/discharge behavior of the two-electrode NGP/PANI supercapacitor at constant current density of 1.4 A/g, is presented in Figure 5B. The charge/discharge time interval 9
ACCEPTED MANUSCRIPT
has been kept constant. As shown in Figure S5, the resulting curves are not fully linear, and the observed sweep can be attributed to the pseudocapacitive behavior of the PANI component. From the galvanostatic data, the specific capacitance is calculated according to the equation Csp=2I∆t/(m∆V), where I is the applied discharge current, ∆t is the discharging time period for the
RI PT
potential change ∆V, ∆V=Vmax-0.5Vmax, and m is average active mass of one electrode including the mass of SDBS surfactant [34]. After 1000 cycles, the specific capacitance for the NGP/PANI
device is 82 F g-1, while the specific capacitance for the pure NGP device is only 10 F g-1. The
SC
cycling measurements cause an increase in the capacitance up to 250 cycles. It can be possibly
related to a cycling measurement induced improvement in the surface wetting of the electrode, leading to more electroactive surface area [35]. The specific capacitance value for NGP/PANI still
M AN U
persists after 1000 cycles, highlighting the good electrochemical stability of the materials used. The combination of high NGP conductivity along with PANI reversible redox properties is regarded as necessary to achieve supercapacitor with long cycle-life.
The reason for the rather moderate capacitance of current supercapacitor is probably due to the SDBS surfactant contained in the NGP and NGP/PANI electrodes and thus, the SDBS may lead to
TE D
the “dead surface” in the printed electrode and thus, may limit the efficient charging/discharging of the supercapacitor [36]. Further improvement in the ink formulation and supercapacitor performance is under study. Most importantly, the performances of printed NGP/PANI thin films
electronics”. 4. Conclusion
EP
show them to be viable candidates for the manufacture of energy storage devices in “printed
AC C
In conclusion, it is shown that NGP/PANI inks can be formulated successfully; and a
commercially scalable inkjet printing technique used to prepare thin-film electrodes with superior control over pattern geometry and pattern location when compared to preparation techniques such as Meyer rod coating methods. The supercapacitors formed with NGP/PANI electrode exhibit good electrochemical performance and a long cycle life. The key result of this work is the applicability of the inkjet printing technique used and the formulation of NGP/PANI from cheap and abundant, commercially available materials to allow an industrially scalable route to achieving printable energy storage devices. 10
ACCEPTED MANUSCRIPT
Acknowledgements The authors would like to thank Thomas Kolb and Waldemar Bartuli for supercapacitor measurements. This work was financially supported by a Marie-Curie Fellowship within the frame of the GENIUS project (FP7 – PEOPLE Programme).
RI PT
Electronic Supplementary Information (ESI) is available from the Online Library or from the author. References
SC
[1] M. Winter, R. J. Brodd, Chem. Rev. 104 (2004) 4245-4269. [2] F. El-Kady, V. S. Sergey Dubin, B. Kaner, Science 16 (2012)1326-1330.
[3] Y. Jung, B. Karimi, G. Hahm, M. Ajayan, J. Jung, Scientific Reports 2 (2012) 773.
M AN U
[4] P. C. Chen, H. T. Chen, J. Qiu, C. W. Zhou, Nano Res. 3 (2010) 594-603.
[5] M. Kaempgen, C. K. Chan, J. Ma, Y. Cui, G. Gruner, Nano Lett. 9 (2009) 1872-1876. [6] L. B. Hu, J. W. Choi, Y. Yang, S. Jeong, F. La Mantia, L. F. Cui, Y. Cui, PANS 106 (2009) 21490-21494.
[7] H. Yan, Z. H. Chen, Y. Zheng, C. Newman, J. R. Quinn, F. Dotz, M. Kastler, A. Facchetti,
TE D
Nature 457 (2009) 679-686.
[8] H. M. Lee, H. B. Lee, D. S. Jung, J. Y. Yun, S. H. Ko, S. B. Park, Langmuir 28 (2012) 1312713135.
[9] X. Pi, L. Zhang, D. Yang, J. Phys. Chem. C 116 (2012) 21240-21243.
EP
[10] V. Dua, S. P. Surwade, S. Ammu, S. R. Agnihotra, S. Jain, K. E. Roberts, S. Park, R. S. Ruoff, S. K. Manohar, Angew. Chem. Int. Ed. 49 (2010) 2154-2157.
AC C
[11] P. Simon, Y. Gogotsi, Nat. Mater. 7 (2008) 845-854. [12] E. Frackowiak, F. Beguin, Carbon 39 (2001) 937-950. [13] Y. Zhu, S. Murali, M. D. Stoller, K. J. Ganesh, W. W. Cai, P. J. Ferreira, A. Pirkle, R. M. Wallace, K. A. Cychosz, M. Thommes, D. Su, E. A. Stach, R. S. Ruoff, Science 332 (2011) 15371541. [14] Y. Huang, J. Liang, Y. Chen, Small 8 (2012)1805-1834. [15] H. S. Schniepp, J. Li, M. J. McAllister, H. Sai, M. Herrera-Alonso, D. H. Adamson, R. K. Prud'homme, R. Car, D. A. Saville, I. A. Aksay, J. Phys. Chem. B 110 (2006) 8535-8539 11
ACCEPTED MANUSCRIPT
[16] M. M. McAllister, J. Li, D. H. Adamson, H. C. Schniepp, A. A. Abdala, J. Liu, M. HerreraAlonso, D. L. Milius, R. Car, R. K. Prud'homme, I. A. Aksay, Chem. Mater. 19 (2007) 4396-4404. [17] C. Liu, Z. Yu, D. Neff, A. Zhamu, B. Z. Jang, Nano Lett. 10 (2010) 4863-4868.
[19] B. Z. Jang, A. Z., United States Patent 2010, US2010055025A.
RI PT
[18] B. Z. Jang, A. Z., United States Patents 2010, US2010056819A.
[20] Y. Wang, Z. Shi, Y. Huang, Y. Ma, C. Wang, M. Chen, Y. Chen, J. Phys. Chem. C 113 (2009)13103-13107.
SC
[21] J. Zhang, X. Zhao, J. Phys. Chem. C 116 (2012) 5420-5426.
[22] K. Zhang, L. Zhang, X. Zhao, J. Wu, Chem. Mater. 22 (2010) 1392-1401.
(2011)1844-1851.
M AN U
[23] S. Das, A. S. Wajid, J. L. Shelburne, Y. Liao, M. J. Green, ACS Appl. Mater. Interfaces 3
[24] Q. Wu, Y. Xu, Z. Yao, A. Liu, G. Shi, ACS Nano 4 (2010) 1963-1970. [25] Y. Xu, M. Schwab, A. Strudwick, I. Hennig, X. Feng, Z. Wu, K. Müllen, Adv. Energy Mater. 3 (2013) 1035-1040..
[26] Y. Xu, Z. Liu, X. Zhang, Y. Wang, J. Tian, Y. Huang, Y. Ma, X. Zhang, Y. Chen, Adv.
TE D
Mater. 21 (2009) 1275–1279.
[27] F. Torrisi, T. Hasan, W. P. Wu, Z. P. Sun, A. Lombardo, T. S. Kulmala, G. W. Hsieh, S. J. Jung, F. Bonaccorso, P. J. Paul, D. P. Chu, A. C. Ferrari, ACS Nano 6 (2012) 2992-3006. [28] M. Singh, H. M. Haverinen, P. Dhagat, G. E. Jabbour, Adv. Mater. 22 (2010) 673-685.
EP
[29] D. Li, J. Huang, R. B. Kaner, Acc. Chem. Res. 42 (2009) 135-145. [30] S. Stankovich, D. A. Dikin, R. D. Piner, K. A. Kohlhaas, A. Kleinhammes, Y. Jia, Y. Wu, S.
AC C
T. Nguyen, R. S. Ruoff, Carbon 45 (2007) 1558-1565. [31] J. An, J. Liu, Y. Zhou, H. Zhao, Y. Ma, M. Li, M. Yu, S. Li, J. Phys. Chem. C 116 (2012) 19699-19708.
[32] N. A. Kumar, H. J. Choi, Y. R. Shin, D. W. Chang, L. M. Dai, J. B. Baek, ACS Nano 6 (2012)1715-1723. [33] D. Wang, F. Li, J. Zhao, W. Ren, Z. Chen, J. Tan, Z. Wu, I. Gentle, G. Lu, H. Cheng, ACS Nano 3 (2009) 1745-1752. [34] M. D. Stoller, R. S. Ruoff, Energy Environ. Sci. 3 (2010) 1294-1301. 12
ACCEPTED MANUSCRIPT
[35] H. Wang,; C. M. B. Holt, Z. Li, X. Tan, B. S. Amirkhiz, Z. Xu, B. C. Olsen, T. Stephenson, D. Mitlin, Nano Res. 5 (2012) 605-617.
AC C
EP
TE D
M AN U
SC
RI PT
[36] C. Zhou, Y. Zhang, Y. Li, J. Liu, Nano Lett. 13 (2013) 2078−2085.
13
ACCEPTED MANUSCRIPT
Supplementary Information Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline
RI PT
Inks Yanfei Xu1*, Ingolf Hennig 2, Dieter Freyberg3, Andrew James Strudwick1, Matthias Georg Schwab1, Thomas Weitz3, Kitty Chih-Pei Cha1
SC
Materials
Nano graphene platelet (NGP, “N002-PDR”) is purchased from Angstron Materials
M AN U
Inc., the NGP thickness is ~1-10 nm, electrical conductivity is around 50-75 S/cm, when measured in form of a compressed pellet. Polyaniline (CAS Number 25233-301, 556459 Aldrich) is purchased from Sigma-Aldrich. The polyaniline (emeraldine base, undoped) average molecular weight is ~5000, electrical conductivity is ~10-9 S/cm. Sodium dodecylbenzenesulphonate (SDBS) is purchased from Sigma-Aldrich.
TE D
The flexible carbon substrates (H2315 IX 11) are purchased from Freudenberg. All materials are used as purchased.
Instruments and measurements
EP
Ultrasonic experiments are carried out using an ultrasonic processor (UP400S, Hielscher, 400 watts, 24 kHz), and sonotrodes (Spitze H7). Surface tension
AC C
measurement is carried out using Tensiometer Lauda (TE2 Lauda with ring diameter 2cm). The printing experiments are carried out using an inkjet Printer (Microdrop, MD-K-140, nozzle diameter 100 µm). Viscosity is measured by HAAKE analytical instruments, using a 60 mm Ø, 0.5o cone and plate. Scanning electron microscope (SEM) measurements are carried out with a Zeiss Ultra 55 (FE-SEM), operated at 5 kV. Nitrogen adsorption and desorption isotherm measurements are carried out at 77 K with a Quantachrom Autosorb 6B analyzer. Raman spectra are taken with an NT-
ACCEPTED MANUSCRIPT
MDT NTEGRA Raman spectrometer (grating with 600 lines/mm used) with an Argon Ion laser operating at a wavelength of 514 nm. A 20X optical objective is used to focus the laser spot which is filtered to 10% of its maximum power using a neutral
RI PT
density filter (leading to ~1 mW power on the sample surface). The exposure time used is 100 s.
Viscosity Measurement: In order to investigate the flow behavior of the inks, we perform rheological measurements using the rheometer and the cone-plate equipment.
SC
Flow curves are carried out by increasing the shear rate from 1 to 3000 s-1. This
M AN U
enables us to determine the high and low shear viscosity regime of our samples. BET measurement: Nitrogen adsorption and desorption isotherm measurements are carried out at 77 K with a Quantachrom Autosorb 6B analyzer. Before the measurements, the samples are dried for 2 h at 80 oC.
In a symmetric two-electrode system, the NGP/PANI electrodes (diameter 2 cm) on
TE D
the carbon fabric substrate are assembled in a stainless steel supercapacitor cell with titanium electrodes. All electrochemical measurements are carried out using 1 M H2SO4 as the electrolyte. The electrochemical impedance spectroscopy, cyclic and
galvanostatic
EP
voltammetry,
charge-discharge
were
measured
AC C
electrochemical workstation IM6eX Zahner Elektrik at room temperature.
on
an
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
Figure S1. (A) AFM image of NGP. (B) AFM image of NGP/PANI. Analysis of a large number of NGP/PANI images reveal that most of the continuous sheets have lateral dimensions of hundreds of nanometers with heights in the range 40-80 nm.
AC C
EP
Figure S2. The viscosity vs. shear rate curves for NGP and NGP/PANI based inks.
Figure S3. Schematic illustration of the inkjet printing process. The thin film thickness is controlled by the printing times. The NGP/PANI dry thin film thickness (5 printing times measured on quartz) is typically ~30 µm.
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
Figure S4. The NGP/PANI patterns are inkjet-printed on the carbon fabric substrate (5 prints).
AC C
EP
Figure S5. Galvanostatic charge-discharge curves of NGP/PAN thin-film electrodes.
S0378-7753(13)01602-9
DOI:
10.1016/j.jpowsour.2013.09.096
Reference:
POWER 18058
To appear in:
Journal of Power Sources
Received Date: 25 May 2013 Revised Date:
14 September 2013
Accepted Date: 24 September 2013
Please cite this article as: Y. Xu , I. Hennig, D. Freyberg, A. James Strudwick, M. Georg Schwab, T. Weitz, K. Chih-Pei Cha, Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline Inks, Journal of Power Sources (2013), doi: 10.1016/j.jpowsour.2013.09.096. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Highlights (POWER 18058) (1) Graphene/polyaniline (NGP/PANI) inks have been formulated successfully.
RI PT
(2) NGP/PANI electrodes are produced by inkjet-printed technology. (3) Two-electrode supercapacitors are fabricated using NGP/PANI electrodes.
(4) Supercapacitors show high electrochemical performance and a long cycle life.
AC C
EP
TE D
M AN U
SC
(5) The above results show a promising field of printed supercapacitors.
ACCEPTED MANUSCRIPT
Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline Inks Yanfei Xu1*, Ingolf Hennig2, Dieter Freyberg3, Andrew James Strudwick1, Matthias Georg Schwab1, Thomas Weitz3, Kitty Chih-Pei Cha1
RI PT
Dr. Y. Xu, Dr. A. Strudwick, Dr. M. Schwab, Dr. K. Cha, Carbon Materials Innovation Center, GVM/I, BASF SE, 67056 Ludwigshafen, Germany Dr. I. Hennig, GMC/R, BASF SE, 67056 Ludwigshafen, Germany
D. Freyberg, Dr. T. Weitz, GVE/F, BASF SE, 67056 Ludwigshafen, Germany
SC
*Corresponding author Tel/ fax: +49 621 6095198 [email protected]
Abstract: In this work, graphene/polyaniline (NGP/PANI) inks are formulated; inkjet printing
M AN U
technology is then used to produce NGP/PANI thin-film electrodes from these inks. With this inkjet printing, good control over a number of key film properties including pattern geometry, pattern location, film thickness, and electrical conductivity is achieved. Two-electrode supercapacitors are fabricated using these thin-film electrodes. Electrochemical measurements with a 1M H2SO4 electrolyte yield a maximum specific capacitance of 82 F g-1, power density of
TE D
124 kW kg-1 and energy density of 2.4 Wh kg-1 when a scan rate of 20 mV s-1 is applied. The supercapacitors show a long cycle life over 1000 cycles. Keyword: graphene/polyaniline ink, inkjet printing, thin-film electrode, supercapacitor, industrial
1. Introduction
EP
applicability.
Continuing advances in the miniaturization of electronic devices has resulted in an increased
AC C
demand for rechargeable power sources that can be rapidly charged and have a long cycle life [1]. To provide peak power, conventional charge storage devices, such as batteries, need to be bulky and heavy, and are not suitable for use in the next generation of portable electronic devices, which are required to be lightweight, ultrathin, and fully flexible [2,3]. As a consequence, lightweight supercapacitors with the advantages of high power density, high energy density and long cycle life are considered to be one of the most promising energy storage devices to satisfy future energy storage needs.
1
ACCEPTED MANUSCRIPT
Printable energy storage devices are of great interest for industrial applications in terms of commercially viable energy storage products and can be produced on a large scale via solution based roll-to-roll methods [4]. Recent successful alternative methods include a spray method to produce SWNT thin film electrodes for supercapacitors [5], and use of the Meyer rod coating
RI PT
method to spread carbon nanotubes on paper for use in both supercapacitors and lithium ion batteries [6]. However, the above mentioned methods typically produce continuous films with no control over geometry and position. Inkjet printing provides the capability of printing films in
SC
controlled geometries and at specific locations on various substrates as it is a direct write process. Inkjet printing methods have been used as one of the key technologies in the fields of organic transistors [7], light-emitting devices [8], solar cells [9], and sensors [10]. To date there have been
addresses this key application.
M AN U
few reports on the production of energy storage devices via inkjet printing [4], the present work
Since the performance of inkjet-printable supercapacitor electrode is strongly governed by the ink that is applied during the process, it is therefore necessary to investigate which materials are best suited for the functional ink formulation. The large surface area and high electrical
TE D
conductivity of graphene makes this versatile carbon material promising for the ink formulation and practical electric double-layer capacitor (EDLC) applications [11-14]. Recent work by several groups produced curved nano graphene platelets (NGP) by oxidation of graphite according to a modified Hummers’ method followed by a subsequent thermal shock exposure exfoliation method
EP
[15-19]. The specific capacitances of these NGP based supercapacitors in an ionic liquid electrolyte are 100-250 F g-1, with an energy density of 85.6 Wh kg-1. This shows a great
AC C
improvement on the previous best result of 28.5 Wh kg-1 obtained elsewhere using graphene materials produced via the hydrazine reduction of graphene oxide [20]. Conducting polymers are another promising electrode material for supercapacitors due to their
high pseudocapacitance [21]. The pseudocapacitance originates from the conducting polymer undergoing fast and reversible faradic redox reactions. As a typical conducting polymer, polyaniline (PANI) has long been a very favorable material for supercapacitor electrode due to its ease of synthesis, processability, and special redox activity [21,22]. However, one of the drawbacks for PANI as supercapacitor electrode is its poor cycling stability because PANI is 2
ACCEPTED MANUSCRIPT
usually brittle and weak in mechanical strength. Additionally, PANI exhibits only moderate electrical conductivity. Graphene has been used as an excellent substrate to host active polymer nanomaterial [23], to overcome these drawbacks of PANI, NGP can also serve as a stable and underlying conductive
RI PT
network for the PANI when combining the NGP and PANI together [22,24]. As such, high capacitance and improved stability is expected to be achieved with NGP/PANI hybrid materials. It
is attractive to formulate NGP/PANI inks to harness these excellent synergistic capacitive
SC
properties.
Here, we formulate NGP/PANI inks and demonstrate the fabrication of supercapacitor electrodes via inkjet printing of these inks. The electrochemical properties of the supercapacitors
impedance spectroscopy techniques. 2. Experimental section 2.1 NGP ink production
M AN U
are investigated by means of cyclic voltammetry (CV), galvanostatic charge discharge and
For the NGP ink production, NGP powder (200 mg), SDBS surfactant (200 mg) and H2O (100
TE D
mL) are added to a glass bottle. The mixture is then probe ultrasonicated for 1 hour (400 watts, 24 kHz), at 10 oC. After this process, the above solution is centrifugated at 500 rpm for 10 minutes; the supernatant is collected and used as the NGP ink. 2.2 NGP/PANI ink production
EP
In a similar process to above the NGP inks are formulated by, NGP powder (200 mg), SDBS surfactant (200 mg) and H2O (100 mL) are added to a glass bottle. The mixture is then probe
AC C
ultrasonicated for 1 hour (400 watts, 24 kHz), at 10 oC. After this process, PANI (200 mg) is added to the above mixture, and probe ultrasonicated for 30 minutes (400 watts, 24 kHz), at 10 oC. Finally, the above solution is centrifugated at 500 rpm for 10 minutes; the supernatant is collected and used as NGP/PANI ink. 2.3 Inkjet printing experiment Inkjet printing experiment is performed at room temperature, the printing parameters are as follows: A voltage of 86 V is used along with a pulse length of 40 µs, the strobe delay is 400 µs, at a frequency of 500 Hz, and a pressure of -5 mbar. The printing is carried out with a grid size of 3
ACCEPTED MANUSCRIPT
800 points, and a grid distance of 0.013 mm. After the printing process, the samples are dried for 2 hours at 80 oC. The weight of the NGP/PANI electrode materials (1.5 mg/cm2) is calculated from the difference in weight between the substrate weight before printing and the substrate weight after printing.
RI PT
3. Results and discussion
The presence of oxygen-containing groups in NGP renders it strongly hydrophilic and water
soluble [25]. Results of atomic force microscopy (AFM, Supporting Information, Figure S1) have
SC
confirmed that NGP can be easily “unfolded” by applying liquid-assisted exfoliation procedures [25,26]. Transmission electron microscopy (TEM) characterization also confirm that NGP and NGP/PANI materials can be dispersed homogenously in water and consist of very thin exfoliated
M AN U
sheets as indicated by their high translucency to the electrons used in TEM analysis shown in
TE D
Figure 1A and 1B.
Figure 1. (A) TEM image of NGP. (B) TEM image of NGP/PANI. TEM results confirm that
EP
NGP, NGP/PANI material can be dispersed homogenously in water, which consists of single and few-layers crumpled NGP sheets.
AC C
As the key property of inks viable for inkjet printing is their ability to generate droplets, it is
very important to prevent nozzle clogging during the inkjet printing. Therefore, the quality of ink depends highly on the NGP/PANI particle size, the ink surface tension and especially the viscosity of the ink. From AFM analysis it can be seen that a wrinkle-like structure exists in the NGP and that the platelets have a typical thickness of 5-10 nm (Figure S1A). And analysis of a large number of NGP/PANI images revealed that most of the continuous sheets have lateral dimensions of hundreds of nanometers with heights in the range 40-80 nm, as shown in Figure S1B. The surface tension values for the NGP and NGP/PANI inks are 34 and 36 mN m-1 respectively. The 4
ACCEPTED MANUSCRIPT
NGP and NGP/PANI inks used herein show a viscosity of around 1 mPa•s observed at a shearing rate of 300-3000 s-1 (Figure S2). From the surface tension and viscosity results we conclude that the ink formulation used in this work fits the inkjet-printing requirements [27]. Next, we turn to the description of the inkjet printing process that is applied in this study. The
RI PT
inkjet printing process involves the ejection of a fixed quantity of ink from a chamber, via a nozzle
due to a sudden, quasi-adiabatic reduction of the chamber volume via piezoelectric action (Figure
S3). The chamber, filled with liquid, is contracted in response to application of an external voltage.
SC
This sudden reduction causes a shockwave in the liquid, which leads to the ejection of a liquid
drop from the nozzle. The ejected drop falls until it impinges on the substrate, spreads under
then dries through solvent evaporation [28].
M AN U
momentum acquired in the motion, and surface tension aided flow along the surface. The drop
A common challenge with inkjet printing is the inability to produce thin and homogeneous films. Here we show that these problems can be avoided with electrically conductive NPG and NGP/PANI films obtained on quartz substrates merely through multiple prints over the same pattern. The NGP/PANI thin film is printed on the quartz substrate, and the conductivity for the
TE D
NGP thin film (5 prints, thickness ~41µm) is 3.67 S/cm (99 Ohm/sq), while the conductivity for the NGP/PANI thin film (5 prints, thickness ~28 µm) is 0.29 S/cm (846 Ohm/sq), while the pure PANI conductivity is only 10-9 S/cm [29].
In addition, homogeneous NGP/PANI thin films can be easily printed on the carbon fabric
EP
substrate, with good control over pattern geometry and location (Figure S4). Compared with quartz substrates, conductive carbon fabric substrates dramatically improve film adhesion even
AC C
without binder, and simplify the coating process due to the fibrous paper-like structure of the material. Moreover, as the carbon fabric substrates are electrically conductive, NGP/PANI thin films printed on these substrates can be used as electrodes directly for supercapacitor devices. Raman spectroscopy (Figure 2) is used to study the surface compositions of the NGP and
NGP/PANI films. NGP shows two distinctive peaks centered at ~1363 cm-1 and ~1590 cm-1 that correspond to D and G bands, respectively [30]. Three new representative peaks arising from PANI can be indexed at 1184, 1234, 1508 cm-1, apart from the D/G bands of graphene. They correspond to the C-H bending vibration of benzenoid rings, C-N stretching vibration of 5
ACCEPTED MANUSCRIPT
benzenoid rings, and stretching vibrating of C=N in quinonoid ring systems of PANI [31]. PANI
SC
RI PT
is possibly adsorbed onto the surface of NGP by π-π stacking [32].
Figure 2. Raman spectrum of NGP and NGP/PANI thin films. A 20X optical objective is used to
M AN U
focus the laser spot which is filtered to 10% of its maximum power using a neutral density filter (leading to ~1 mW power on the sample surface). The exposure time used is 100 s. Figure 3 shows scanning electron microscope (SEM) images of the surface of NGP and NGP/PANI thin films that have been printed onto the carbon fabric substrates. The NGP formed homogeneous networks on the substrate surface, as shown in Figures 3A and 3C. Figures 3B and 3D show the cross section of the NGP and NGP/PANI thin films. NGP exhibits a layer structure
TE D
on the conductive substrate, keeping the advantage of the entangled network of the NGP that also
AC C
EP
promotes good access of the electrolyte to the active PANI material.
Figure 3. (A) SEM surface images of NGP thin film on carbon substrate. (B) SEM cross section images of the NGP thin films on the substrate. (C) SEM surface images of NGP/PANI thin film on carbon substrate. (D) SEM cross section images of the NGP/PANI thin films on the substrate. 6
ACCEPTED MANUSCRIPT
Nitrogen adsorption-desorption analysis is used to determine the specific surface area of the NGP and NGP/PANI thin films. The corresponding values are 69 m2 g-1 and 287 m2 g-1 respectively, while the specific surface area for pure PANI and blank carbon substrate is only 34 and 2 m2 g-1 respectively [20,33]. We suggest that the adsorption of PANI can serve as spacer to
RI PT
further separate NGP neighboring sheets, increases the specific surface area of NGP. This is favorable for increasing the EDLC of supercapacitors.
Using best-practice methods for determining an electrode material’s performance for
SC
supercapacitors, we constructed and measured the performance of two-electrode symmetrical
supercapacitor devices on the basis of NGP/PANI electrodes and H2SO4 electrolyte [13]. Two asprinted NGP/PANI electrodes on carbon fabric substrate are used as electrodes without any further
M AN U
treatment, and sandwiched together with a separator to form an electrochemical capacitor, using a 1M H2SO4 electrolyte, as shown in Figure 4A. The printed NGP/PANI films on carbon substrates used in the fabrication of supercapacitors are typically 5 prints. It should be noted that the two electrode supercapacitor test fixture configuration closely matches the performance of a packaged supercapacitor cell[34]. The NGP/PANI thin film is used as an active electrode, with the carbon
TE D
fabric substrate serving as a current collector (Supporting Information for the supercapacitor test cells setup details). The electrochemical behaviors of the resulting supercapacitors are investigated by CV methods. Figures 4B and 4C show the CV results of NGP and NGP/PANI electrodes obtained at different scan rates. The redox peaks of NGP/PANI films are attributed to the redox of
PANI,
corresponding
EP
transition
to
its
leucoemeraldine/emeraldine
and
emeraldine/pernigraniline structural conversions [25]. This observation additionally confirms the
AC C
presence of pseudocapacitive PANI in the electrodes. There is an increase in the current density at high scan rate; this demonstrates good conductivity
and capacitive behavior of the NGP and NGP/PANI electrodes [24]. The specific capacitance (Csp) is calculated based on the integrated area of the CV discharge curves yielding an average discharge current (Id). Csp = 2 C/m (C is the measured capacitance for the two-electrode cell C=Id/(dV/dt), and m is the average mass of one electrode, including the mass of SDBS surfactant). At a high scan rate of 20 mV s-1, the NGP/PANI supercapacitor delivers a specific capacitance of 70 F g-1 (Figure 4D), while the NGP based supercapacitor delivers a specific capacitance of 10 F 7
ACCEPTED MANUSCRIPT
g-1. These measurement results show the synergistic effect of NGP/PANI resulting from the
M AN U
SC
RI PT
pseudocapacitance of PANI and from the physical charge storage contribution of the NGP.
Figure 4 (A) Supercapacitor device structure. (B) CV curves of NGP electrodes measured at
TE D
different scan rates, in 1M H2SO4 electrolyte, two-electrode system. (C) CV curves of NGP/PANI electrodes measured at different scan rates, in 1M H2SO4 electrolyte, two-electrode system. (D) Specific capacitance as a function of scan rate in two electrode system, with 1M H2SO4 aqueous
EP
electrolyte.
In Figure 5A, the Nyquist plot of supercapacitors with NGP/PANI electrodes show a straight
AC C
line in the low-frequency region and an unconspicuous arc in the high frequency region. These plots do not show semicircle regions, probably due to the low faradaic resistances of the NGP/PANI electrode [24]. The high frequency part of NGP/PANI shows a Warburg type impedance behavior and is related to the diffusion of ions within the porous structure.[20]. The vertical shape at lower frequencies indicates a purely capacitive behavior; the more vertical the curve, the more closely the supercapacitor behaves as an ideal capacitor. The equivalent series resistance (ESR), as estimated from the intercept of the curve on the x-axis, is about 0.28 Ω (Figure 5A inset). The ESR measurement can be used to estimate the rate at which the 8
ACCEPTED MANUSCRIPT
supercapacitor can be charged-discharged, and it is an important factor in determining the power density of the device. Consequently, the maximum power density of the supercapacitor has been calculated according to the equation Pmax=Vmax2/4MR, where Vmax is the maximum voltage, R is the ESR and M is the mass of the two electrodes [20]. The energy density E is given by:
RI PT
E=CVmax2/2M. With a cell voltage of 1.0 V, the NGP/PANI supercapacitor exhibits a high power density of 124 kW kg-1, with an energy density of 2.4 Wh kg-1 at a scan rate of 20 mV s-1 (this
value was calculated based on the active material including SDBS surfactant.). In comparison, the NGP supercapacitor exhibits power density of 132 kW kg-1, with an energy density of 0.3 Wh kg-1
AC C
EP
TE D
M AN U
SC
at a scan rate of 20 mV s-1.
Figure 5 (A) Nyquist plots of NGP and NGP/PANI supercapacitor device. (B) Cycling stability of the supercapacitor device over 1000 cycles, cycling stability measured at a constant current density of 1.4 A/g, with 1M H2SO4 electrolyte. To further confirm the merits of the NGP/PANI thin films as supercapacitor electrodes, a typical galvanostatic charge/discharge behavior of the two-electrode NGP/PANI supercapacitor at constant current density of 1.4 A/g, is presented in Figure 5B. The charge/discharge time interval 9
ACCEPTED MANUSCRIPT
has been kept constant. As shown in Figure S5, the resulting curves are not fully linear, and the observed sweep can be attributed to the pseudocapacitive behavior of the PANI component. From the galvanostatic data, the specific capacitance is calculated according to the equation Csp=2I∆t/(m∆V), where I is the applied discharge current, ∆t is the discharging time period for the
RI PT
potential change ∆V, ∆V=Vmax-0.5Vmax, and m is average active mass of one electrode including the mass of SDBS surfactant [34]. After 1000 cycles, the specific capacitance for the NGP/PANI
device is 82 F g-1, while the specific capacitance for the pure NGP device is only 10 F g-1. The
SC
cycling measurements cause an increase in the capacitance up to 250 cycles. It can be possibly
related to a cycling measurement induced improvement in the surface wetting of the electrode, leading to more electroactive surface area [35]. The specific capacitance value for NGP/PANI still
M AN U
persists after 1000 cycles, highlighting the good electrochemical stability of the materials used. The combination of high NGP conductivity along with PANI reversible redox properties is regarded as necessary to achieve supercapacitor with long cycle-life.
The reason for the rather moderate capacitance of current supercapacitor is probably due to the SDBS surfactant contained in the NGP and NGP/PANI electrodes and thus, the SDBS may lead to
TE D
the “dead surface” in the printed electrode and thus, may limit the efficient charging/discharging of the supercapacitor [36]. Further improvement in the ink formulation and supercapacitor performance is under study. Most importantly, the performances of printed NGP/PANI thin films
electronics”. 4. Conclusion
EP
show them to be viable candidates for the manufacture of energy storage devices in “printed
AC C
In conclusion, it is shown that NGP/PANI inks can be formulated successfully; and a
commercially scalable inkjet printing technique used to prepare thin-film electrodes with superior control over pattern geometry and pattern location when compared to preparation techniques such as Meyer rod coating methods. The supercapacitors formed with NGP/PANI electrode exhibit good electrochemical performance and a long cycle life. The key result of this work is the applicability of the inkjet printing technique used and the formulation of NGP/PANI from cheap and abundant, commercially available materials to allow an industrially scalable route to achieving printable energy storage devices. 10
ACCEPTED MANUSCRIPT
Acknowledgements The authors would like to thank Thomas Kolb and Waldemar Bartuli for supercapacitor measurements. This work was financially supported by a Marie-Curie Fellowship within the frame of the GENIUS project (FP7 – PEOPLE Programme).
RI PT
Electronic Supplementary Information (ESI) is available from the Online Library or from the author. References
SC
[1] M. Winter, R. J. Brodd, Chem. Rev. 104 (2004) 4245-4269. [2] F. El-Kady, V. S. Sergey Dubin, B. Kaner, Science 16 (2012)1326-1330.
[3] Y. Jung, B. Karimi, G. Hahm, M. Ajayan, J. Jung, Scientific Reports 2 (2012) 773.
M AN U
[4] P. C. Chen, H. T. Chen, J. Qiu, C. W. Zhou, Nano Res. 3 (2010) 594-603.
[5] M. Kaempgen, C. K. Chan, J. Ma, Y. Cui, G. Gruner, Nano Lett. 9 (2009) 1872-1876. [6] L. B. Hu, J. W. Choi, Y. Yang, S. Jeong, F. La Mantia, L. F. Cui, Y. Cui, PANS 106 (2009) 21490-21494.
[7] H. Yan, Z. H. Chen, Y. Zheng, C. Newman, J. R. Quinn, F. Dotz, M. Kastler, A. Facchetti,
TE D
Nature 457 (2009) 679-686.
[8] H. M. Lee, H. B. Lee, D. S. Jung, J. Y. Yun, S. H. Ko, S. B. Park, Langmuir 28 (2012) 1312713135.
[9] X. Pi, L. Zhang, D. Yang, J. Phys. Chem. C 116 (2012) 21240-21243.
EP
[10] V. Dua, S. P. Surwade, S. Ammu, S. R. Agnihotra, S. Jain, K. E. Roberts, S. Park, R. S. Ruoff, S. K. Manohar, Angew. Chem. Int. Ed. 49 (2010) 2154-2157.
AC C
[11] P. Simon, Y. Gogotsi, Nat. Mater. 7 (2008) 845-854. [12] E. Frackowiak, F. Beguin, Carbon 39 (2001) 937-950. [13] Y. Zhu, S. Murali, M. D. Stoller, K. J. Ganesh, W. W. Cai, P. J. Ferreira, A. Pirkle, R. M. Wallace, K. A. Cychosz, M. Thommes, D. Su, E. A. Stach, R. S. Ruoff, Science 332 (2011) 15371541. [14] Y. Huang, J. Liang, Y. Chen, Small 8 (2012)1805-1834. [15] H. S. Schniepp, J. Li, M. J. McAllister, H. Sai, M. Herrera-Alonso, D. H. Adamson, R. K. Prud'homme, R. Car, D. A. Saville, I. A. Aksay, J. Phys. Chem. B 110 (2006) 8535-8539 11
ACCEPTED MANUSCRIPT
[16] M. M. McAllister, J. Li, D. H. Adamson, H. C. Schniepp, A. A. Abdala, J. Liu, M. HerreraAlonso, D. L. Milius, R. Car, R. K. Prud'homme, I. A. Aksay, Chem. Mater. 19 (2007) 4396-4404. [17] C. Liu, Z. Yu, D. Neff, A. Zhamu, B. Z. Jang, Nano Lett. 10 (2010) 4863-4868.
[19] B. Z. Jang, A. Z., United States Patent 2010, US2010055025A.
RI PT
[18] B. Z. Jang, A. Z., United States Patents 2010, US2010056819A.
[20] Y. Wang, Z. Shi, Y. Huang, Y. Ma, C. Wang, M. Chen, Y. Chen, J. Phys. Chem. C 113 (2009)13103-13107.
SC
[21] J. Zhang, X. Zhao, J. Phys. Chem. C 116 (2012) 5420-5426.
[22] K. Zhang, L. Zhang, X. Zhao, J. Wu, Chem. Mater. 22 (2010) 1392-1401.
(2011)1844-1851.
M AN U
[23] S. Das, A. S. Wajid, J. L. Shelburne, Y. Liao, M. J. Green, ACS Appl. Mater. Interfaces 3
[24] Q. Wu, Y. Xu, Z. Yao, A. Liu, G. Shi, ACS Nano 4 (2010) 1963-1970. [25] Y. Xu, M. Schwab, A. Strudwick, I. Hennig, X. Feng, Z. Wu, K. Müllen, Adv. Energy Mater. 3 (2013) 1035-1040..
[26] Y. Xu, Z. Liu, X. Zhang, Y. Wang, J. Tian, Y. Huang, Y. Ma, X. Zhang, Y. Chen, Adv.
TE D
Mater. 21 (2009) 1275–1279.
[27] F. Torrisi, T. Hasan, W. P. Wu, Z. P. Sun, A. Lombardo, T. S. Kulmala, G. W. Hsieh, S. J. Jung, F. Bonaccorso, P. J. Paul, D. P. Chu, A. C. Ferrari, ACS Nano 6 (2012) 2992-3006. [28] M. Singh, H. M. Haverinen, P. Dhagat, G. E. Jabbour, Adv. Mater. 22 (2010) 673-685.
EP
[29] D. Li, J. Huang, R. B. Kaner, Acc. Chem. Res. 42 (2009) 135-145. [30] S. Stankovich, D. A. Dikin, R. D. Piner, K. A. Kohlhaas, A. Kleinhammes, Y. Jia, Y. Wu, S.
AC C
T. Nguyen, R. S. Ruoff, Carbon 45 (2007) 1558-1565. [31] J. An, J. Liu, Y. Zhou, H. Zhao, Y. Ma, M. Li, M. Yu, S. Li, J. Phys. Chem. C 116 (2012) 19699-19708.
[32] N. A. Kumar, H. J. Choi, Y. R. Shin, D. W. Chang, L. M. Dai, J. B. Baek, ACS Nano 6 (2012)1715-1723. [33] D. Wang, F. Li, J. Zhao, W. Ren, Z. Chen, J. Tan, Z. Wu, I. Gentle, G. Lu, H. Cheng, ACS Nano 3 (2009) 1745-1752. [34] M. D. Stoller, R. S. Ruoff, Energy Environ. Sci. 3 (2010) 1294-1301. 12
ACCEPTED MANUSCRIPT
[35] H. Wang,; C. M. B. Holt, Z. Li, X. Tan, B. S. Amirkhiz, Z. Xu, B. C. Olsen, T. Stephenson, D. Mitlin, Nano Res. 5 (2012) 605-617.
AC C
EP
TE D
M AN U
SC
RI PT
[36] C. Zhou, Y. Zhang, Y. Li, J. Liu, Nano Lett. 13 (2013) 2078−2085.
13
ACCEPTED MANUSCRIPT
Supplementary Information Inkjet-Printed Energy Storage Device Using Graphene/Polyaniline
RI PT
Inks Yanfei Xu1*, Ingolf Hennig 2, Dieter Freyberg3, Andrew James Strudwick1, Matthias Georg Schwab1, Thomas Weitz3, Kitty Chih-Pei Cha1
SC
Materials
Nano graphene platelet (NGP, “N002-PDR”) is purchased from Angstron Materials
M AN U
Inc., the NGP thickness is ~1-10 nm, electrical conductivity is around 50-75 S/cm, when measured in form of a compressed pellet. Polyaniline (CAS Number 25233-301, 556459 Aldrich) is purchased from Sigma-Aldrich. The polyaniline (emeraldine base, undoped) average molecular weight is ~5000, electrical conductivity is ~10-9 S/cm. Sodium dodecylbenzenesulphonate (SDBS) is purchased from Sigma-Aldrich.
TE D
The flexible carbon substrates (H2315 IX 11) are purchased from Freudenberg. All materials are used as purchased.
Instruments and measurements
EP
Ultrasonic experiments are carried out using an ultrasonic processor (UP400S, Hielscher, 400 watts, 24 kHz), and sonotrodes (Spitze H7). Surface tension
AC C
measurement is carried out using Tensiometer Lauda (TE2 Lauda with ring diameter 2cm). The printing experiments are carried out using an inkjet Printer (Microdrop, MD-K-140, nozzle diameter 100 µm). Viscosity is measured by HAAKE analytical instruments, using a 60 mm Ø, 0.5o cone and plate. Scanning electron microscope (SEM) measurements are carried out with a Zeiss Ultra 55 (FE-SEM), operated at 5 kV. Nitrogen adsorption and desorption isotherm measurements are carried out at 77 K with a Quantachrom Autosorb 6B analyzer. Raman spectra are taken with an NT-
ACCEPTED MANUSCRIPT
MDT NTEGRA Raman spectrometer (grating with 600 lines/mm used) with an Argon Ion laser operating at a wavelength of 514 nm. A 20X optical objective is used to focus the laser spot which is filtered to 10% of its maximum power using a neutral
RI PT
density filter (leading to ~1 mW power on the sample surface). The exposure time used is 100 s.
Viscosity Measurement: In order to investigate the flow behavior of the inks, we perform rheological measurements using the rheometer and the cone-plate equipment.
SC
Flow curves are carried out by increasing the shear rate from 1 to 3000 s-1. This
M AN U
enables us to determine the high and low shear viscosity regime of our samples. BET measurement: Nitrogen adsorption and desorption isotherm measurements are carried out at 77 K with a Quantachrom Autosorb 6B analyzer. Before the measurements, the samples are dried for 2 h at 80 oC.
In a symmetric two-electrode system, the NGP/PANI electrodes (diameter 2 cm) on
TE D
the carbon fabric substrate are assembled in a stainless steel supercapacitor cell with titanium electrodes. All electrochemical measurements are carried out using 1 M H2SO4 as the electrolyte. The electrochemical impedance spectroscopy, cyclic and
galvanostatic
EP
voltammetry,
charge-discharge
were
measured
AC C
electrochemical workstation IM6eX Zahner Elektrik at room temperature.
on
an
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
Figure S1. (A) AFM image of NGP. (B) AFM image of NGP/PANI. Analysis of a large number of NGP/PANI images reveal that most of the continuous sheets have lateral dimensions of hundreds of nanometers with heights in the range 40-80 nm.
AC C
EP
Figure S2. The viscosity vs. shear rate curves for NGP and NGP/PANI based inks.
Figure S3. Schematic illustration of the inkjet printing process. The thin film thickness is controlled by the printing times. The NGP/PANI dry thin film thickness (5 printing times measured on quartz) is typically ~30 µm.
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
Figure S4. The NGP/PANI patterns are inkjet-printed on the carbon fabric substrate (5 prints).
AC C
EP
Figure S5. Galvanostatic charge-discharge curves of NGP/PAN thin-film electrodes.