A Consecutive Spray Printing Strategy to Construct and Integrate

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A Consecutive Spray Printing Strategy to Construct and Integrate Diverse Supercapacitors on Various Substrates Xinyu Wang, Qiongqiong Lu, Chen Chen, Mo Han, Qingrong Wang, Haixia Li, Zhiqiang Niu, and Jun Chen ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b08833 • Publication Date (Web): 03 Aug 2017 Downloaded from http://pubs.acs.org on August 4, 2017

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ACS Applied Materials & Interfaces

A Consecutive Spray Printing Strategy to Construct and Integrate Diverse Supercapacitors on Various Substrates Xinyu Wang,† Qiongqiong Lu,† Chen Chen,† Mo Han,† Qingrong Wang,† Haixia Li,† Zhiqiang Niu,*,† and Jun Chen†,‡ †

Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of

Chemistry, Nankai University, Tianjin, 300071, P.R. China. ‡

Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai

University, Tianjin, 300071, China.

KEYWORDS: supercapacitor; carbon nanotube; printable; spray printing; diverse structures.

ABSTRACT: The rapid development of printable electronic devices with flexible and wearable characters requires supercapacitor devices to be printable, light, thin, integrated macro- and micro-devices with flexibility. Herein, we developed a consecutive spray printing strategy to controllably construct and integrate diverse supercapacitors on various substrates. In such strategy, all supercapacitor components are fully printable, and their thicknesses and shapes are well controlled. As a result, supercapacitors obtained by this strategy achieve diverse structures and shapes. In addition, different nanocarbon and pseudo-capacitive materials are applicable for the fabrication of these diverse supercapacitors. Furthermore, the diverse supercapacitors can be

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readily constructed on various objects with planar, curved or even rough surface (e.g. plastic film, glass, cloth and paper). More importantly, the consecutive spray printing process can integrate several supercapacitors together in the perpendicular and parallel directions of one substrate by designing the structure of electrodes and separators. It enlightens the construction and integration of fully printable supercapacitors with diverse configurations to be compatible with fully printable electronics on various substrates.

1. Introduction Printable electronics is an emerging field in which electronic devices are usually prepared in a large area on diverse substrates by a variety of processing techniques such as film casting, inkjet printing, spray coating and screen printing.1,

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Currently, some devices, such as transistors,

organic light-emitting diodes, solar cells have been successfully achieved by a direct printing technique.3-6 These printable electronics generally possess three main important features: flexibility, diverse structures and consecutive printing process based on inks.7, 8 To obtain fully printable electronic systems, as an essential component of these systems, their energy storage devices have to possess above features of printable electronics to match them. Among various energy storage devices, supercapacitors have attracted much attention due to their high power and energy densities, and long cycle life.9,

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Therefore, fully printable supercapacitors with

diverse structures on various substrates should be considered. Recently, considerable efforts have been made in the design of printable supercapacitors on different substrates.11-20 However, there are still three remaining issues in the rational design of fully printable supercapacitors with diverse structures on the desired substrates. The first problem is that the printing assembly of all supercapacitor components such as electrode materials, separator and electrolyte is inconsecutive and their orientation is not controlled well.12


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In general, the thin CNT film electrodes were often fabricated by a spraying method. However, after that, the thin film electrodes were often first coated onto the substrates and then the commercial separator and/or gel electrolyte were sandwiched between electrodes on substrates to assemble supercapacitor devices.11, 16, 20 As a result, it cannot engineer all the components of supercapacitors into diverse structures and shapes onto one substrate by a consecutive printing technology and the orientation of supercapacitor components is not tailored. The second problem lies in the limitation of diversity of objective substrate selection.18 In some cases of flexible or wearable electronic system, the substrates with curved and/or rough surfaces are generally used and the supercapacitors have to be integrated with such substrates. Owing to the limitation of suitable integrating approach, all supercapacitor components are hard to be integrated onto the bulky substrates with curved and/or rough surface, impeding the practical application of printable supercapacitors.21, 22 The last one is that different printable supercapacitors cannot be integrated together by interconnecting in series and/or parallel on various substrates during the printing process to improve the output potential and/or current.23 Considering above issues, consecutively and controllably engineering all supercapacitor components on various substrates to integrate the supercapacitors with diverse configurations and shapes is desired. In this work, we present a consecutive spray printing strategy to consecutively and controllably assemble all supercapacitor components, including electrode materials, separator and electrolyte into fully printable supercapacitors on the desired substrates. The fully printable supercapacitors could be readily designed with diverse configurations and shapes on various objects with planar, curved or even rough surfaces, such as plastic film, glass, cloth and paper. In addition, various supercapacitor electrode materials with distinctively different sizes, shapes and properties can be utilized in this method. Importantly, the fully printable process can integrate


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several supercapacitors together on one substrate with a curved and/or rough surface in series or parallel by designing the structures of the electrodes and separators. Therefore, the fully printable supercapacitors with diverse structures and shapes would be well compatible with the integrated electronics system on various substrates. 2. Experimental 2.1 Preparation of SWCNT, CNF and SWCNT/PANI inks The single-walled carbon nanotubes (SWCNTs, Carbon Solutions Inc.) were dispersed in N, N-dimethyl formamide (~2 mg ml-1) with a bath ultrasonator for 2 h. After standing for more than 24 h, the supernatant dispersion of SWCNT solution was used as the SWCNT ink. Cellulose nanofiber (CNF) dispersion (Haojia Nanofiber Tech. Co. LTD, Tianjin) was diluted with deionized water to obtain a concentration of 0.18 wt%. Polyaniline (PANI) nanofibers were prepared as previously reported literature.24 The PANI nanofibers were directly added into the SWCNT suspension to obtain the mixed ink, followed by ultrasonication. The mass ratio of SWCNT to PANI in their inks was controlled in 1:0 to 1:0.5, 1:1, 1:1.5 and 1:2, respectively. 2.2 Fabrication of fully printable supercapacitors. The substrates were covered by the shadow mask with designed pattern to obtain the SWCNT films with desired shape. The SWCNT ink was first spray coated by a hand-held airbrush (IWATA HP-CH) onto pre-heated substrates (e.g. plastic film, glass, cloth and paper) at 90 oC with different number of spray cycles. After each spray, a pause of 5-10 s should be taken for the film to be dried. The mass of the SWCNT films coated on the substrate was measured by weighing the substrates before and after the spray deposition. The CNF ink was then sprayed onto the surface of SWCNT films (size: 1.5×1.5 cm) and dried to form CNF film (size: 2.3×2.3 cm) serving as the separator. After that, another SWCNT film (size: 1.5×1.5 cm) was prepared


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onto the CNF film by a similar spray printing process to act as another electrode of supercapacitor device.

Two devices in parallel were assembled by repeating above spray

printing process of SWCNT and CNF inks. Subsequently, the polyvinyl alcohol (PVA)/H2SO4 and PVA/LiCl gel electrolyte that was prepared according to our previously report

25, 26

was

sprayed onto the top of SWCNT and CNF films at room temperature. Finally, the fully printable thin supercapacitor devices with gel electrolyte were left at room temperature for several hours to diffuse PVA/H2SO4 electrolyte from the top to the bottom and remove the residual solvents, and then encapsulated with thin plastic wrap to obtain the fully printable supercapacitors with diverse configurations on various substrates. 2.3 Characterization The morphologies of fully printable supercapacitors were characterized by field-emission scanning electron microscopy (SEM, JEOL JSM7500F). The thickness of SWCNT films was measured via atomic force microscopy (AFM, Bruker MultiMode Icon). The cyclic voltammetry (CV) and leakage current curves of the supercapacitors were tested on a CHI660E electrochemical workstation (CHI Instruments). The galvanostatic charge/discharge (GCD) curves and cycling life measurement of the supercapacitors were carried out on a supercapacitor test system (Arbin, 2000BT). The resistances of SWCNT films on the substrates were measured by a four-point probe meter (RTS-8). Electrochemical impedance spectrum (EIS) curves were performed in the frequency range from 100 kHz to 10 mHz on an electrochemical workstation (Zennium E, Zahner Elektrik GmbH & Co. KG). 3. Results and discussion A schematic illustration depicting the experimental process of constructing the fully printable supercapacitor by consecutive spray printing is presented in Figure 1a. In a typical experiment,


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SWCNT ink was first sprayed onto the substrate that covered by a shadow mask with designed pattern to obtain SWCNT film with desired shape as one of the supercapacitor electrodes. Subsequently, the CNFs were coated seamlessly onto the surface of SWCNT film to serve as the separator by a similar spray process based on CNF ink (step I of Figure 1a). After that, the SWCNT ink was further sprayed onto the CNF film to act as another electrode of supercapacitor device (step II of Figure 1a). The desired shape of printable supercapacitor depends on the pattern of shadow mask. Afterwards, PVA/H2SO4 electrolyte was sprayed on the top of SWCNT and CNF films (step III of Figure 1a). Subsequently, the supercapacitor device was left at room temperature for the diffusion of PVA/H2SO4 electrolyte from the top to the bottom and removes the residual solvents, obtaining the fully printable supercapacitors on the substrates (Figure 1d). During the spray printing process, a number of atomized SWCNT droplets would sprinkle onto the pre-heated substrate through the desired mask. Simultaneously, the solvent in the SWCNT droplets that reach the substrate was evaporated fast, leaving SWCNTs on the substrate and forming SWCNT film, as depicted in Figure 2a. The SWCNT film shows a porous entangled network (Figure 1b), which would be significant for the accessibility of electrolyte and the transport of the electrons.27 Owing to the strong van der Waals forces between SWCNTs and substrates, the SWCNT film has good mechanical adhesion with the substrate.28, 29 To illustrate such adhesion between SWCNT film and the substrate, the SWCNT film on the substrate was tried to peer off by a Scotch tape, and no SWCNTs were visualized on the tape (Figure S1). As a result, the substrate-supported SWCNT films can be bent without any cracking and peeling off. Furthermore, the thickness of the SWCNT films can be dominated by the concentration of the SWCNT ink and the number of spray printing cycles. The SWCNT films with different thicknesses were prepared by varying the number of spraying cycles at a constant concentration


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of the SWCNT ink (Figure S2). The thickness of the SWCNT films increases almost linearly with the number of spraying cycles, with an average increase of ~ 5.5 nm per cycle (Figure 2b). The sheet resistances (R) of SWCNT films are related to their thicknesses (t) and can be fitted by the following formula:30, 31

σ = 1 / Rt

(1)

where σ is the electrical conductivity. The best fitted electrical conductivity was 624 S cm-1 (Figure 2c). Such a high electrical conductivity of the SWCNT films will have a contribution to the fast electron transport during charge/discharge process.32 Clearly, the resistance of SWCNT films on substrates will affect their performance as the electrodes of supercapacitors.33 To serve as the flexible supercapacitor electrodes, stable sheet resistance of SWCNT films at different bending states is required. Therefore, the sheet resistance of SWCNT films on different substrates, including polyethylene terephthalate (PET) film, cellulose fiber paper and cloth, was measured at different bending levels. The SWCNT films on these substrates show nearly unchanged sheet resistance at different bending states (Figure 2d). To demonstrate their stable electrical conductivity, SWCNT films on cloth were typically used as the connecting wire to illuminate a light emitting diode (LED). They worked well at a high bending state (Inset in Figure 2d). CNF is an ecofriendly material with high flexibility, low cost and easily printing on appropriate substrates.34 Stable suspension of CNFs can be prepared in large amounts via a process of oxidation.35,

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The homogeneous CNF aqueous suspension will be a potential

candidate of the separator ink.37 Therefore, the CNF film was prepared by the spray printing using the CNF ink for the separator of fully printable supercapacitor. Since the thicknesses of SWCNT and CNF films were well controlled, the thickness of a representative supercapacitor


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could reach about 10 µm (Figure 1c), which is much thinner than the commercial standard A4 print paper (typically 90-100 µm). Furthermore, the thin thickness will contribute to the flexibility of whole integrated devices.38 The thin electrode and separator films could also reduce ion diffusion length during charge/discharge process, which will be beneficial to the electrochemical performance of the fully printable thin supercapacitors.39, 40 The CV curves of a representative supercapacitor device have a typical rectangular shape at scan rates from 10 to 100 mV s-1 (Figure 3a), indicating the pure double-layer capacitive behavior.41 The CV results agree well with the GCD curves, which maintain nearly triangular shape (Figure 3b). The specific capacitance (Cspe) of the SWCNT film electrodes using PVA/H2SO4 and PVA/LiCl as electrolyte respectively is 124 F g-1 and 108 F g-1 at a current density of 0.2 A g-1 (Figure S3a). In addition, the equivalent series resistance could also be obtained from GCD measurement. The value of equivalent series resistance is 26 Ω (Figure S3b), which is smaller than that of the electrode material using highly viscous CNT-ink (80 Ω).42 Owing to the progressively diffusion-limited of ions into the porous films at a higher current density, the specific capacitance of SWCNT films gradually decreases to 92 F g-1 at a current density of 5 A g-1, retaining about 74% of specific capacitance at 0.2 A g-1 (Figure S3c), which is higher than reported values of SWCNT-based electrodes.43,

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This result indicates the

excellent rate performance of the fully printable thin supercapacitors due to the shortened diffusion path lengths of the electrolyte ions and the low equivalent series resistance of the electrode material. Furthermore, it is important to evaluate the leakage current of supercapacitor devices for practical application. The supercapacitor displays a smaller leakage current of about 8.1 µA (Figure S3d), leading to the high stability of our supercapacitor devices.42 In order to demonstrate the flexibility of the printable supercapacitors on PET film, the CV curves of a


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representative printable supercapacitor were measured at different bending states. There is almost no significant deviation in the CV curves when L/L0 (where L0 is the initial length of substrate with printable supercapacitor, and L is the distance between two ends of substrate at different bending states) is changed from 1 to 0.2 (Figure 3c). Furthermore, the stability of the flexible supercapacitors was measured under different bending times. The specific capacitance of the supercapacitor is almost not altered in spite of repeated bending 200 times (Figure S3e,f). These results suggesting that printable supercapacitor on PET substrate is quite stable under bending states and they are suitable for the flexible device applications. The electronic devices have a trend towards unconventional and diverse shapes.23 To match these electronic devices, unconventional shaped supercapacitors have to be constructed. By designing the masks, the consecutive spray printing is emerged as a versatile and effective method to prepare various shaped supercapacitors.14, 45 As a proof of concept, a supercapacitor written “NKU” (Figure 1e) was fabricated to show the aesthetic shapes accessible using the consecutive spray printing strategy. Furthermore, the “NKU” shaped supercapacitor remained the ability to deliver normal charge/discharge behavior (Figure S4). The specific capacitance of SWCNT film electrodes is stable but relatively low due to their energy store mechanism of electric double-layer capacitor. Compared to the electric double-layer capacitors, pseudo-supercapacitors usually provide a higher energy density.46-48 Among various pseudo-capacitive materials, PANI is one of the potential candidates since its fast and reversible faradic redox reactions. In addition, PANI was often added into nanocarbon materials to obtain the composite electrodes, which exhibit an enhanced performance due to a synergistic effect by combining the virtues of the two types of materials.49-51 Therefore, PANI nanofibers were used as a typical pseudo-capacitive material to mix in the SWCNT ink to fabricate the SWCNT-PANI


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composite film electrodes. In the SWCNT-PANI composite films, SWCNTs still remain a continuous network structure and the PANI nanofibers were well distributed in the composite film (Figure S5a) , demonstrating the universal applicability of the developed spay printable strategy for the fabrication of printable supercapacitor electrodes based on various active materials. In addition, the electrochemical performance of printable supercapacitors depends on the amount of PANI in the SWCNT-PANI films. SWCNT-PANI inks with different weight ratios of 1:0 to 1:0.5, 1:1, 1:1.5 and 1:2 were used to fabricate the electrodes of printable supercapacitors. Their CV curves show a rectangular curve superimposed with two pair of redox peaks, attributing to the redox of PANI (Figure 3d and Figure S5b). When the mass ratio of SWCNT to PANI is 1:1.5, the specific capacitance of SWCNT-PANI films can reach up to 322 F g-1 at 20 mV s-1, which is nearly 3.5 times higher than that of the pure SWCNT electrodes (Figure 3e). Furthermore, there is only a very slight difference in their CV curves at different bending states (Figure S5c). The specific capacitance of the supercapacitors based on SWCNTPANI composite films lost only about 2.9 % even at a high bending level (Figure 3f). Therefore, although the addition of pseudo-capacitive material can effectively improve the electrochemical performance of thin supercapacitors based on nanocarbon material electrodes, but it nearly have no impact on the flexibility of the printable supercapacitors. These results strengthen the suggestion that the consecutive spray printing will be an appropriate strategy to fabricate fully printable supercapacitors based on various active materials. To extend the application of printable electronic devices, they have been successfully constructed on various substrates.52 Therefore, it is desired that the printable supercapacitors with different structures and shapes can be assembled on the corresponding substrates to match these printable electronic devices. In our spray printing strategy, the printing process of all


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supercapacitor components is independent of the objective substrates. Therefore, the consecutive spray printing will be a versatile technique to construct the fully printable supercapacitors on various substrates. As a proof of concept, we fabricated the thin supercapacitors on another three typical substrates of daily use beside the PET substrate discussed above, including glass, cloth and paper (Figure 4a-4c). Glass represents a typical hard flat substrate.53 Cloth based on textile materials may be an ideal wearable substrate with a rough surface.54 Paper is often considered as a good candidate of substrate with porous structure and better flexibility compared to PET.55 The electrochemical performances of the fully printable thin supercapacitors on various substrates were also compared. CV curves of the supercapacitors on different substrates are revealed with slight distinction in shape (Figure 4d) due to the amount of SWCNT electrodes well controlled by the same number of spray printing cycles. It is also suggested by the GCD curves with similar discharge time (Figure S6). The specific capacitance of the SWCNT film electrodes on these substrates is in a range of about 120-129 F g-1 (Figure 4e). It is higher or comparable in comparison with various printable supercapacitors based on nanocarbon materials, such as carbon nanotube, activated carbon and reduced graphene oxides (Table S1), demonstrating the universal applicability of consecutive spray printing for fabricating printable supercapacitors on different substrates. More importantly, the supercapacitors on flexible substrates display stable electrochemical performance at different bending states (Figure 4f), indicating that they can serve as flexible energy storage devices on various substrates. The total energy in a single supercapacitor is often too low to meet their practical applications to power other electrical devices. Thus, more supercapacitors have to be integrated together either in parallel, in series, or in combinations of the two to output higher voltage and current.56 Recently, the integration of supercapacitors are only achieved in a parallel direction on flat


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substrates due to the limitation of suitable integrating approach. It will be of great significance to assemble the supercapacitors in a perpendicular direction of substrates and/or on the coarse or curved surface to overcome the limitation of parallel space. The spray printing process of SWCNT and CNF inks is similar to a layer-by-layer assembly. Repeated step I and II of Figure 1a, more SWCNT film electrodes and CNF film separators can achieved layer by layer to realize the assembly of more supercapacitor devices in the direction perpendicular to the surface of the substrate. As a proof of concept, two parallel supercapacitor devices that are composed with four SWCNT film electrodes and three CNF film separators (Figure 5a,b) are assembled by the consecutive spray printing technology. The discharge time of the two supercapacitor devices in parallel is twice than that of the single supercapacitor at the same current density (Figure 5c). This result is also confirmed by their integral area of CV curves at 100 mV s-1 (Figure S7a). To better understand the electrochemical behavior of the single device and two devices in parallel, the EIS was measured and shown as a Nyquist plot (Figure S7b). A vertical plot at lower frequencies indicates a pure capacitive behavior and represents the ion diffusion in the electrode structure (Inset in Figure S7b). In addition, the specific capacitance (normalized to 1) of two supercapacitor devices in parallel is nearly unchanged for 2000 cycles, which is similar with the case of single supercapacitor device (Figure S7c). The GCD curves of printable supercapacitors at a bending state are only slight difference in comparison with that at no bending state (Figure S7d). These indicate that the integration of printable supercapacitors nearly has no impact on the electrochemical performance of the fully printable supercapacitor system even under a bending state. The multiple stacking of supercapacitors can be combined in parallel to tailor the current. It is noted that there are no restrictions to the size and topology of all supercapacitor components in the consecutive spray printing. It suggests that multiple fully printable


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supercapacitors can be also easily integrated together by designing the structures of each supercapacitor component layer, whether the substrates have a coarse or curved surface.21, 57 As a proof of concept, we designed four supercapacitors into one unit in series on a cloth, as depicted in Figure 5d. The resultant integrated supercapacitor unit on a white coat was powerful enough to light up a red LED when fully changed demonstrating the excellent applicability and compatibility of wearable electronics (Figure 5e). In addition to the planar substrates, using the consecutive spray printing strategy, the integrated thin supercapacitor unit in series could also be fabricated on curved surface. A reagent bottle was selected as a representative curved substrate to prepare the integrated thin supercapacitor unit in series, which can also power a red LED (Figure 5f). The electrochemical performances of integrated supercapacitor units on cloth and reagent bottle were also studied by CV and GCD experiments. The CV curves of the supercapacitor units display a nearly rectangular shape even the potential could be up to 3.2 V, which is four times than that of a single supercapacitor (Figure 5g,h and Figure S8a). The GCD curves of the integrated supercapacitor units show a nearly linear and symmetric shape in the tested voltage window (0-3.2 V), which exhibits perfect capacitive behavior (Figure 5i, Figure S8b). This result reveals that the consecutive spray printing technology easily allows the voltage of the resultant integrated supercapacitors to be controlled by simply integrating several printable supercapacitors on one a coarse or curved substrate. 4. Conclusions In summary, a consecutive spray printing strategy to controllably assemble all supercapacitor components, including electrode materials, separator and electrolyte on the desired substrates was developed to construct the fully printable supercapacitors. The structures and shapes of fully printable supercapacitors can be tailored and diverse. Furthermore, in such strategy, various


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objects with planar, curved or even rough surface (e.g. plastic film, glass, cloth and paper) can serve as the substrate to support the fully printable supercapacitors and different nanocarbon and pseudo-capacitive materials can be utilized to fabricate the diverse supercapacitors. In addition, the consecutive spray printing process can integrate several supercapacitors together in the perpendicular and parallel directions of one substrate with planar, curved or even rough surface. The integrated architecture would not only increase the density of thin supercapacitor devices on one substrate, but also reduce the complexity of the intricate interconnect among supercapacitor devices. Therefore, such consecutive spray printing strategy provides a route to construct and integrate diverse energy storage devices with the merits of printability, designability, lightweight, flexibility and high electrochemical performances on various substrates.


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Supporting Information. Detailed experimental procedures and additional materials characterization. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (21573116, 51602218 and 21231005), MOE (B12015 and IRT13R30), Tianjin Basic and High-Tech Development (15JCYBJC17300). Z. Niu thanks the recruitment program of global experts.


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Figure 1. (a) Schematic diagram of preparing a fully printable supercapacitor by a consecutive spray printing process. (b) SEM image of SWCNT film electrode. (c) Cross-sectional SEM and (d) optical images of a fully printable supercapacitor. (e) Optical image of a “NKU” shaped supercapacitor.


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Figure 2. (a) Schematic process of preparing SWCNT films directly on a substrate using a spray printing method. (b) The thickness of the SWCNT films with different number of spray cycles. (c) The sheet resistance of the SWCNT films with different thicknesses. The solid line is fitting result by the formula 1. (d) The normalized sheet resistance of SWCNT films on PET, cloth and paper at different bending states, where R0 and L0 are the initial resistance and length of SWCNT films, respectively; R and L are the resistance and the distance between two ends of SWCNT films under different bending states, respectively. Insets: optical images of an LED illuminated by SWCNT films on cloth as the connecting wire at different bending states.


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Figure 3. (a) The CV curves of a printable supercapacitor at different scan rates. (b) The GCD curves of a printable supercapacitor at varying current densities. (c) The CV curves of a printable supercapacitor on PET under different values of L/L0, where L0 is the initial length of substrates, and L is the distance between two ends of films in different bending states. (d) The CV curves of supercapacitors based on SWCNT-PANI film electrodes with different mass ratios, 20 mV s-1. (e) The specific capacitances (Cspe) of SWCNT-PANI film electrodes with different mass ratios. (f) The normalized specific capacitance of supercapacitors based on pure SWCNT and SWCNTPANI composite film with the mass ratio of 1:1.5 as electrodes under different bending states.


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Figure 4. Optical images of thin supercapacitors integrated on (a) glass, (b) cloth, (c) paper. (d) The CV curves of thin supercapacitors on different substrates. Scan rate: 100 mV s-1. (e) The specific capacitance of SWCNT film electrodes (Cspe) on different substrates at a current density of 0.5 A g-1. (f) The normalized specific capacitance of thin supercapacitors on PET, cloth and paper under different states, where L0 is the initial length of substrates, and L is the distance between two ends of films in different bending states.


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Figure 5. (a) Optical and (b) cross-sectional SEM images of two supercapacitors in parallel integrated in the perpendicular direction to the surface of the substrate. (c) The GCD curves of two supercapacitors in parallel and a single supercapacitor at a current density of 0.5 A g-1. (d) SWCNT and CNF film patterns on a coarse or curved surface for assembling four supercapacitors into one unit in series. Optical images of a LED illuminated using four supercapacitors in series on (e) a white coat and (f) a reagent bottle. (g) The CV curves of four supercapacitors on cloth in series at different scan rates. (h) The CV curves of four supercapacitors in series and a single supercapacitor on cloth at the scan rate of 100 mV s-1. (i) The GCD curves of the four supercapacitors in series and a single supercapacitor on cloth at 0.5 A g-1.


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TOC A Consecutive Spray Printing Strategy to Construct and Integrate Diverse Supercapacitors on Various Substrates Xinyu Wang, Qiongqiong Lu, Chen Chen, Mo Han, Qingrong Wang, Haixia Li, Zhiqiang Niu,* and Jun Chen A consecutive spray printing strategy to controllably integrate all supercapacitor components, including electrode materials, separator and electrolyte is developed to construct fully printable supercapacitors with diverse structures and shapes on various objects, even on a coarse or curved surface.


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A Consecutive Spray Printing Strategy to Construct and Integrate

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