Patterning Island-Like MnO2 Arrays by Breath Figure Templates for

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Patterning Island-Like MnO2 Arrays by Breath Figure Templates for Flexible Transparent Supercapacitors Yizhou Wang, Weixin Zhou, Qi Kang, Jun Chen, Yi Li, Xiaomiao Feng, Dan Wang, Yanwen Ma, and Wei Huang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b06710 • Publication Date (Web): 12 Jul 2018 Downloaded from http://pubs.acs.org on July 14, 2018

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ACS Applied Materials & Interfaces

Patterning Island-Like MnO2 Arrays by Breath Figure

Templates

for

Flexible

Transparent

Supercapacitors Yizhou Wang, Weixin Zhou, Qi Kang, Jun Chen, Yi Li*, Xiaomiao Feng, Dan Wang, Yanwen Ma*, Wei Huang Key Laboratory for Organic Electronics and Information Displays & Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.

ABSTRACT Though plenty of active materials could be used as supercapacitor electrodes, only limited ones have been engineered to construct transparent supercapacitors. Specially, it is a great challenge to make the opaque metal oxides，which often owns high energy density，into transparent films. Here we demonstrate a novel approach to fabricate transparent MnO2 films for flexible transparent supercapacitors. By utilizing breath-figure polymer films with ordered pores as template, arrays of MnO2 islands were electrochemically deposited, with high light

ACS Paragon Plus Environment

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transmission. The thickness and interspace distance of MnO2 island arrays could be adjusted by tuning deposition time, so that the capacitance and transparency of the electrodes are changed accordingly. Such island array structure can effectively eliminate the internal stress existed in the composite film to avoid cracks during bending operation. The assembled transparent supercapacitor shows a transmittance of 44% at 550 nm, and can yield a high capacitance of 4.73 mF/cm2 at a current density of 50 µA/cm2, demonstrating high flexibility and stability.

KEYWORDS: supercapacitors, flexible, transparent, manganese dioxide, electrodeposition, breath figure

1. INTRODUCTION Future electronics, together with their energy storage systems, are anticipated to be more light weighted, portable, flexible and even transparent1-7. Up to date, tremendous researches have been focused on flexible and transparent electronic devices, such as displays8, 9, solar cells10,

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,

batteries12-14 and supercapacitors15-29. Particularly, flexible transparent supercapacitors have developed dramatically in recent years due to their facilely accessible sandwich structure, short charge time, high power density and long cycling life. One general strategy to fabricate flexible transparent supercapacitors is using carbon nanotubes (CNTs)15, 16and graphene19-23 as active materials. The CNT films are able to achieve transparency in the porous network structure, and graphene is intrinsically transparent in one- to few-layer architecture. The capacitance of such flexible transparent supercapacitors depends on the film thickness of the carbon nanomaterials. For example, increasing the thickness of CNTs film will increase the areal capacitance but decrease the transparency inevitably15,

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. Besides, the specific capacitance of these carbon


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nanomaterials, dominating by electric double layer capacitance, is far below the pseudocapacitance of the transition metal oxides, such as MnO230-32, RuO233 and Co3O434. For instance, the theoretical specific capacitance of MnO2 is 1370 F/g, about one-order higher than that of CNTs35. However, it remains a big challenge to tailor these opaque transition metal oxide films into transparent electrodes. In addition, these films are brittle, so they cannot tolerate mechanically bending or twisting36. To solve these problems, the method of patterning transition metal oxides in pore structure was developed. For example, by depositing MnO2 film on Au mesh using polystyrene sphere as template, a flexible transparent electrode was formed27. This MnO2-based flexible transparent supercapacitor had a transparency of 36% at 550 nm and delivered a specific capacitance of 0.795 mF/cm2 at a current density of 5 µA/cm2. In our recent study, honeycomb structured copper mesh was prepared by using breath figure approach, and used as flexible transparent electrodes37. Since breath figure technology is facile and feasible in preparing large area porous polymer films38, in this work, it is employed to fabricate transparent transition metal oxide films as depicted in Figure 1. Here MnO2 is electrochemically deposited onto flexible ITO/PET substrate using the patterned pores in breath-figure polymer film as template, and then the template film is removed to form light transmission zone. The prepared MnO2 island arrays with interspace are able to prevent the formation of cracks—a major issue that hampers the application of metal oxide films in flexible devices. As a result, the assembled all-solid-state sandwich-like flexible transparent supercapacitors show a transparency of 44% at 550 nm and yield a high areal capacitance of 4.73 mF/cm2 at a current density of 50 µA/cm2. Meanwhile, the flexible transparent supercapacitors show high mechanical flexibility and cycling stability, suggesting the great potential of this breath figure approach in the fabrication of metaloxide based flexible electrodes for energy storage devices.


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2.EXPERIMENTAL SECTION Materials Polystyrene-b-poly (acrylic acid) (PS-b-PAA) was synthesized by ATRP method37, 39. Carbon disulfide (CS2), ethyl acetate, poly (vinyl alcohol) (PVA), lithium chloride (LiCl), manganese (II) acetate tetrahydrate (Mn(CH3COO)2·4H2O) and sodium sulfate (Na2SO4) were purchased from Aladdin Reagents. ITO-covered PET were purchased from Huanan Xiangcheng Co. Ltd. All purchased reagents were used without further treatment. Deionized water was obtained by a Milli-Q system (Millipore Corp., Billerica, MA). Preparation of the porous PS-b-PAA film on ITO Ordered porous PS-b-PAA film was prepared by a typical breath figure route. At first, PS-bPAA was dissolved in CS2 solvent with a concentration of 1.5 wt% and then kept at 0 °C by ice bath. An ITO film with 1 min plasma treatment was immersed in the PS-b-PAA solution for 20 s, then lifted up and placed in an environment of 80% relative humidity at 70 °C. The relative humidity was adjusted by controlling by the ratio of dry and humid air and kept by a constant airflow with a speed of 200 cm/min. After dried in air, a perforated porous monolayer PS-b-PAA film on ITO/PET substrate was fabricated. Deposition of MnO2 island arrays on ITO/PET substrate MnO2 was deposited on ITO/PET by a simple potentiostatic electrochemical deposition process. The electrodeposition solution is composed of 0.1 M Mn(CH3COO)2·4H2O and 0.1 M Na2SO4 aqueous solution. During the electrochemical deposition, a piece of PS-b-PAA/ITO/PET plated pretreated by 1 min plasma was used as working electrode, a saturated calomel electrode and a platinum sheet electrode served as reference electrode and counter electrode, respectively.


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The deposition voltage was 1.0 V. After the MnO2 deposition, the PS-b-PAA porous template was removed by immersing the whole film into ethyl acetate for 30 minutes, then washing with ethanol and deionized water in sequence for 5 times. The MnO2 island arrays films with deposition time of 50 s, 100 s, 200 s and 300 s were denoted as MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s, respectively. Fabrication of flexible transparent supercapacitors based on MnO2 island arrays electrodes A transparent supercapacitor consists of two strips of MnO2/ITO electrodes that connected but separated by PVA/LiCl gel electrolyte. The PVA/LiCl electrolyte was prepared by dissolving1 g PVA and 1 g LiCl in 10 mL water with continuous stirring for about 2 h at 85 ℃ to form a liquid gel. The effective working area of the flexible transparent supercapacitors is controlled to be 2 cm2. Materials characterization The PS-b-PAA porous film and the MnO2 island arrays films were characterized by scanning electron microscopy (SEM, Hitachi S-4800), transmission electron microscopy (TEM, FEI Talos F200X field-emission transmission electron microscope operated at 200 kV) equipped with energy-dispersive X-ray spectroscopy (EDS). The thickness of MnO2 island arrays films was measured by Stylus Profiler (Bruker DektakXT). The water contact angles of the samples were measured with3 µL droplet of water using a Krüss DSA100 (KrüssCompany,Germany) apparatus at ambient temperature. The transparency of prepared films was measured by a UV-vis spectrophotometer (PerkinElmer, Lambda 650). The composition of MnO2 was identified by Xray photoelectron spectroscopy (XPS, PHI 5000 VersaProbe) using MnO2/ITO films. Electrochemical measurements


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Electrochemical performances were studied by cyclic voltammetry, galvanostatic charge– discharge and electrical impedance spectroscopy (EIS) on the VMP3 Electrochemical Workstation (Bio-logic). Two-electrode configuration was applied to test the performance of the whole devices, while three-electrode system was carried out to evaluate a single electrode. In three-electrode system, 1 M Na2SO4 solution was used as electrolyte, MnO2/ITO electrode served as working electrode, a platinum sheet and a saturated calomel electrode acted as counter electrode and reference electrode, respectively. The areal capacitance was calculated from the CV curves according to the following equation (1): ‫ܥ‬௦ ൌ

‫ ׬‬ூௗ௏ ௌ௏௩

(1)

Where I is the response current (mA), S is the working area of the supercapacitor (cm2), V is the potential window (V), and ‫ ݒ‬is the scan rate of potential (mV/s). The areal capacitance calculated from the galvanostatic charge–discharge curves was using the following equation (2): ூ௧

‫ܥ‬௦ ൌ ௌ௏

(2)

Where I is the constant discharge current (mA), t is the discharge time (s), S is the working area of the supercapacitor (cm2), and V is the potential window after the internal resistance (IR) drop (V).

Figure 1. Schematic illustration for the fabrication of MnO2 island array electrodes.


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3. RESULTS AND DISCUSSION The morphology of breath-figure PS-b-PAA films on ITO/PET substrates are shown in Figure 2a and 2b. The PS-b-PAA films exhibit a uniform hexagonal pore array morphology, with a pore diameter of 2−3 µm and the spacing skeleton of about 0.4 µm (Figure S1). After the electrodeposition process, island-like MnO2 films with smooth surface appear in the pore region of PS-b-PAA films (Figure 2c, d), indicating the good template effect of breath-figure PS-b-PAA films. When the PS-b-PAA template is removed by ethyl acetate dissolution, MnO2 island arrays with even size and interspace distance are obtained. It is noted that the thickness, size and interspace distance of MnO2 films could be adjusted by simply tuning deposition time. With the increase of deposition time from 50 to 300 s, the thickness and size of the island structure increase, while the interspace distance decreases (Figure 2e-f). In detail, the island size of MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s are 2.44, 2.50, 2.65 and 2.77 µm, respectively, with the corresponding interspace distance of 0.44, 0.41, 0.22 and 0.05 µm. The test result of water contact angles confirms that the MnO2 coverage increases with deposition time (Figure S2). The thickness of MnO2 layer for MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s are evaluated to be about 140, 210, 450 and 610 nm, respectively, which is less than the thickness of PS-b-PAA film (about 1200 nm), as measured by stylus profiler and the cross-sectional SEM images (Figure S3). Since the pores in water-based breath-figure PS-b-PAA polymer films is confirmed in spherical structure40, the size of the deposited MnO2 films within the spherical pores depends on its thickness (Figure S4a). It is clear that in the hollow spherical template, the MnO2 islands deposited at the bottom of the pores have


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a small diameter while those approaching the center of the sphere present the largest diameter, as depicted in Figure S4b-e. This is the reason why with increasing the thickness of MnO2 film, the diameter of the island arrays increased while their interspace distance decreased. The transmittance of MnO2/ITO films with different deposition time is measured by UV–vis spectroscopy, as shown in Figure 2i. For comparison, the transmittance of a bare ITO is also provided. MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s have a transmittance at 550 nm of 68.7%, 55.9%, 43.0%, 25.8%, respectively. The transmittance of the films is determined by the interspace distance and the film thickness. With increasing the interspace distance, the film thickness decreases, meaning the increase of the light transmission in uncoated zone and light scattering through MnO2 thin films. Hence the transmittance is elevated. The MnO2/ITO-50s and MnO2/ITO-100s samples exhibit adequate transparency, as shown by the photographs of films on a paper printed with a color picture in Figure 2j. But MnO2/ITO-200s and MnO2/ITO-300s samples present fuzzy transparency due to the small interspace distance and thick film. The obtained MnO2 films are amorphous, as revealed by results of selected area electron diffraction, with uniform distribution of Mn and O (Figure S5). The elemental and chemical states of as-prepared MnO2 films are analyzed by the XPS spectrum as shown in Figure 3. The O 1s deconvolution leads to three features at about 529.7, 531.4 and 533.2 eV corresponding to Mn-O-Mn, Mn-O-H and H-O-H. The binding-energy separation between Mn 2p1/2 and Mn 2p3/2 is 11.7 eV, and that between Mn 3s is 4.8 eV, indicating the formation of MnO232, 41, 42.


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Figure 2. (a-d) SEM images of the PS-b-PAA template (a, b) and the MnO2/PS-b-PAA on ITO/PET (c, d) at low (a, c) and high (b, d) magnification. (e-h) SEM images, (i) transmittance and (j) digital photos of the MnO2 films with different deposition time on ITO/PET. (e) MnO2/ITO-50s, (f) MnO2/ITO-100s, (g) MnO2/ITO-200s and (h) MnO2/ITO-300s.

Figure 3 XPS spectra of (a) survey scan, (b) O 1s, (c) Mn 2p and (d) Mn 3s


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The supercapacitive performance of the as-prepared MnO2 island array electrodes are measured by three-electrode system in 1 M Na2SO4 solution. The cyclic voltammetry (CV) curves of all samples at a scan rate of 100 mV/s present rectangular-like shape within 0–0.8 V (Figure 4a), and the corresponding galvanostatic charge–discharge (GCD) curves exhibit a triangular profile (Figure 4b), suggesting an ideal capacitive behavior. The current densities of MnO2/ITO samples in CV and GCD curves increase with increasing deposition time, results from the increased loading of MnO2 active materials. Compared with MnO2 island array electrodes, the bare ITO current collector presents a low and negligible capacitance. The areal capacitances of MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s calculated from GCD curves are 1.23, 7.08, 10.01, 13.44 mF/cm2, respectively. This change tendency is consistent with the CV measurement (Figure S6). With increasing scan rate from 10 to 100 mV/s, the CV curves of MnO2/ITO-50s and MnO2/ITO-100s still remain a nearly symmetrical rectangular shape, while those of MnO2/ITO-200s and MnO2/ITO-300s gradually deform from the rectangular shape. The areal capacitance of these samples at various scan rates is calculated from corresponding CV curves and shown in Figure 4c. It is seen that with increasing scan rate, the areal capacitance of MnO2/ITO-200s and MnO2/ITO-300s with thick MnO2 films decrease remarkably. At a high scan


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Figure 4. (a) CV curves, (b) GCD curves, (c) areal capacitances at different scan rates and (d) Nyquist plots of MnO2 island arrays electrodes. (a) Scan rate: 100 mV/s, (b) Current density: 100 µA/cm2. Inset in Figure 4d are the magnified high-frequency region of impedance plot and fitted equivalent circuit, where RS is the series resistance, CDL is the double-layer capacitance, RCT is the charge transfer resistance, CP is the pseudocapacitance, RL is the leakage resistance and WO is the Warburg impedance.

rate of 100 mV/s, the areal capacitance of MnO2/ITO-200s and MnO2/ITO-300s are lower that of MnO2/ITO-100s, due to the slow diffusion of electrolyte in thick MnO2 films. To understand the diffusion effect, the equivalent series resistances (RS) and the charge transfer resistance (RCT) of these electrodes are measured by electrochemical impedance spectroscopy (Figure 4d). The EIS spectra are carried out in the frequency range from 100 kHz to 0.01 Hz at an amplitude of 5 mV. In the low frequency region, the MnO2/ITO-100s sample shows a nearly vertical curve, indicating that its capacitive performance is close to that of an ideal capacitor. The Nyquist plots of samples were fitted by equivalent circuit (the inset of Figure 4d, Figure S7)26, 31, The data


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calculated from fitted equivalent circuit show that the RS of the MnO2/ITO-50s, MnO2/ITO-100s, MnO2/ITO-200s, MnO2/ITO-300s are 38.9, 35.1, 39.42 and 39.9 Ω, respectively, and their RCT are 296.5, 19.1, 74.6 and 165.4 Ω, respectively. MnO2/ITO-50s has high electrical resistance due to the discontinuous film structure (Figure 2e). For samples of MnO2/ITO-100s, MnO2/ITO-200s and MnO2/ITO-300s, the electrical resistance increases with the increasing film thickness (Figure 2f-g). So the MnO2/ITO-100s exhibits much lower RS and RCT, and then the better capacitive performance especially at high scan rate. In view of the transmittance and electrochemical performance of each individual electrode, the MnO2/ITO-100s sample is an optimum electrode for the preparation of full device. Figure 5a shows the schematic of a two-electrode flexible transparent supercapacitors using LiCl/PVA gel as both electrolyte and separator. The assembled devices present a typical capacitance characteristic (Figure 5b). The supercapacitor devices are highly transparent and flexible, as shown in Figure 5c and d. With respect to single MnO2/ITO electrode film having a 55.9% transmittance, this all-solid-state two-electrode supercapacitor exhibits a slightly decreased value of 44.0% at 550 nm (Figure 5c). The devices based on MnO2 island arrays show good flexibility during CV tests at a scan rate of 50 mV/s under different bending states. When the device is bent to 180°, no obvious change in the CV curves is observed and its capacitance still remains 90.2% (1.85 versus 2.05 mF/cm2) (Figure 5d and S8). To understand the merit of MnO2 island arrays in flexibility, a continuous MnO2 film was prepared for comparison in bending test. The unpatterned MnO2 film suffers serious crack once it is bent. In contrast, the patterned MnO2 films with the island array structure exhibits outstanding mechanical and electrochemical stability during repeated bending, similar to the reported nanowire/nanotube array structure43-45 (Figure S9, S10). Figure 5e illustrates the GCD curves of the supercapacitors at various current


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densities, presenting good triangle shapes with a small IR drop. The areal capacitances of device with a current density of 50 µA/cm2 is up to 4.73 mF/cm2, which is at a high level in the state-ofthe-art MnO2 based flexible transparent supercapacitors, and remarkably higher than most flexible transparent supercapacitors based on noble metal nanowires, graphene and CNTs (Table. S1)

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. Figure 5f shows the cycle stability of the device, examining by GCD cycling at a

current density of 50 µA/cm2. The capacitance retains 88.2% (from 4.73 to 4.17 mF/cm2) of its initial value after 1000 charge/discharge cycles, revealing high cycling stability of the device. The capacitance decrease could be attributed to the loss of a small proportion of MnO2, which was caused by volume expansion of MnO2 film during the ion insertion/removal and the dissolution of MnO2 during charge/discharge46-48. A series connection of two devices are used to light up a red LED (the inset in Figure 5f), suggesting their potential application as a micropower supply.


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Figure 5. (a) Schematic illustration of the sandwich-like supercapacitors based on MnO2 island arrays electrodes. (b) CV curves of the device at different scan rates. (c) Transmittance of MnO2/ITO-100s and assembled device. The inset is the digital image of a bendable device. (d) CV curves of the device at different bending angles with a scan rate of 50 mV/s. (e) GCD curves of the device at 50 µA/cm2 and 100 µA/cm2. (f) Cycling stability of the device upon charging/discharging at a current density of 50 µA/cm2. The inset is an LED driven by two devices connected in series. 4. CONCLUSIONS In summary, a novel approach to fabricate metal-oxide array structure for flexible transparent supercapacitors is developed by using breath-figure polymer pattern as template. The MnO2 island arrays are electrochemically deposited into the template pores, resulting in a transparent film after the removal of the template. The transparency of the MnO2 island array film is tuned from 25.8% to 68.7% by altering the interspace distance from 0.05 to 0.44 µm and the film


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thickness from 610 to 140 nm via varying the electrochemical deposition time. The assembled flexible transparent supercapacitor devices based on MnO2 island array electrodes reach a transmittance of 44% at 550 nm and delivered a high areal capacitance of 4.73 mF/cm2 at a current density of 50 µA/cm2. In addition, the devices show good mechanical flexibility and long cycling stability. Considering the similarity between the electrochemical or photochemical deposition approaches of transition metal oxides, the breath-figure templating approach developed in this work should also be applicable to prepare RuO2, NiO, Co3O4 and Fe2O3 island arrays, which will provide versatile electrodes for the construction of transparent flexible symmetric or asymmetric supercapacitors.

ASSOCIATED CONTENT Supporting Information. Digital photo and optical images of breath figure membrane. Water contact angles of samples with different deposition time. SEM of the cross-section view of the samples, schematic illustration of the MnO2 electrodeposition process. HRTEM images and elemental mapping of scraped MnO2. CV curves of different samples in three-electrode system, nyquist plots of different samples after equivalent circuit fitting, capacitance retention of the assembled supercapacitor at different bending angles, digital photos and SEM images of conventional unpatterned MnO2 films compared to island-like MnO2 electrodes, comparison table of performance of sandwich-like transparent supercapacitors based on different active materials. AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (Y. W. Ma)


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*E-mail: [email protected] (Y. Li) Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work is jointly supported by NSFC (51772157, 61504062), Jiangsu Provincial NSF (BK20150863), Priority Academic Program Development of Jiangsu Higher Education Institutions (YX03001), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Synergistic Innovation Center for Organic Electronics and Information Displays, Jiangsu Province “Six Talent Peak” (2014-XCL-014), Qing Lan Project of Jiangsu Province, Graduate Education Innovation Project in Jiangsu Province (CXZZ12_0461), and Scientific Research Foundation of NUPT (NY217004).

REFERENCES (1) Eftekhari, A.; Fan, Z. Y. Ordered Mesoporous Carbon and Its Applications for Electrochemical Energy Storage and Conversion. Mater. Chem. Front. 2017, 1, 1001-1027. (2) Zhu, G. Y.; Chen, J.; Zhang, Z. Q.; Kang, Q.; Feng, X. M.; Li, Y.; Huang, Z. D.; Wang, L. H.; Ma, Y. W. NiO Nanowall-Assisted Growth of Thick Carbon Nanofiber Layers on Metal Wires for Fiber Supercapacitors. Chem. Commun. 2016, 52, 2721-2724. (3) Wang, Y. G.; Song, Y. F.; Xia, Y. Y. Electrochemical Capacitors: Mechanism, Materials, Systems, Characterization and Applications. Chem. Soc. Rev. 2016, 45, 5925-5950. (4) Zhu, K.; Wang, Y.; Tang, J. A.; Guo, S. H.; Gao, Z. M.; Wei, Y. J.; Chen, G.; Gao, Y. A High-Performance Supercapacitor Based on Activated Carbon Fibers with an Optimized Pore Structure and Oxygen-Containing Functional Groups. Mater. Chem. Front. 2016, 1, 958-966. (5) Ma, Y. W.; Li, P.; Sedloff, J. W.; Zhang, X.; Zhang, H. B.; Liu, J. Conductive Graphene Fibers for Wire-Shaped Supercapacitors Strengthened by Unfunctionalized Few-Walled Carbon Nanotubes. ACS Nano 2015, 9, 1352-1359.


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


(6) Liu, Z.; Xu, J.; Chen, D.; Shen, G. Z. Flexible Electronics Based on Inorganic Nanowires. Chem. Soc. Rev. 2015, 44, 161-192. (7) Yuan, K.; Hu, T.; Xu, Y. Z.; Graf, R.; Shi, L.; Forster, M.; Pichler, T.; Riedl, T.; Chen, Y. W.; Scherf, U. Nitrogen-Doped Porous Carbon/Graphene Nanosheets Derived from TwoDimensional Conjugated Microporous Polymer Sandwiches with Promising Capacitive Performance. Mater. Chem. Front. 2016, 1, 278-285. (8) Zhu, B.; Qian, B.; Liu, Y.; Xu, C.; Liu, C.; Chen, Q. Q.; Zhou, J. J.; Liu, X. F.; Qiu, J. R. A Volumetric Full-Color Display Realized by Frequency Upconversion of a Transparent Composite Incorporating Dispersed Nonlinear Optical Crystals. NPG Asia Mater. 2017, 9, e394. (9) Chen, D.; Liu, Z.; Liang, B.; Wang, X. F.; Shen, G. Z. Transparent Metal Oxide Nanowire Transistors. Nanoscale 2012, 4, 3001-3012. (10) Wang, K.; Körstgens, V.; Yang, D.; Hohn, N.; Roth, S. V.; Müller-Buschbaum, P. Morphology Control of Low Temperature Fabricated ZnO Nanostructures for Transparent Active Layers in All Solid-State Dye-Sensitized Solar Cells. J. Mater. Chem. A 2018, 6, 44054415. (11) Cho, A. J.; Park, K.; Park, S.; Song, M. K.; Chung, K. B.; Kwon, J. Y. A Transparent Solar Cell Based on a Mechanically Exfoliated GaTe and InGaZnO p-n Heterojunction. J. Mater. Chem. C 2017, 5, 4327-4334. (12) Wang, J. M.; Zhang, L.; Yu, L.; Jiao, Z. H.; Xie, H. Q.; Lou, X. W.; Sun, X. W. A BiFunctional Device for Self-Powered Electrochromic Window and Self-Rechargeable Transparent Battery Applications. Nat. Commun. 2014, 5, 4921. (13) Yang, Y.; Jeong, S.; Hu, L. B.; Wu, H.; Lee, S. W.; Cui, Y. Transparent Lithium-Ion Batteries. Proc. Natl. Acad. Sci. 2011, 108, 13013-13018. (14) Pan, Q. Y.; Chen, Y. Z.; Zhang, Y. F.; Zeng, D. L.; Sun, Y. B.; Cheng, H. S. A Dense Transparent Polymeric Single Ion Conductor for Lithium Ion Batteries with Remarkable LongTerm Stability. J. Power Sources 2016, 336, 75-82. (15) Gilshteyn, E.; Kallio, T.; Kanninen, P.; Fedorovskaya, E. O.; Anisimov, A. S.; Nasibulin, A. G. Stretchable and Transparent Supercapacitors Based on Aerosol Synthesized Single-Walled Carbon Nanotube Films. RSC Adv. 2016, 6, 93915-93921.


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Page 18 of 22

(16) Kanninen, P.; Luong, N. D.; Sinh, l. H.; Anoshkin, I. V.; Tsapenko, A.; Seppälä, J.; Nasibulin, A. G.; Kallio, T. Transparent and Flexible High-Performance Supercapacitors Based on Single-Walled Carbon Nanotube Films. Nanotechnology 2016, 27, 235403. (17) Chen, F. H.; Wan, P. B.; Xu, H. J.; Sun, X. M. Flexible Transparent Supercapacitors Based on Hierarchical Nanocomposite Films. ACS Appl. Mater. Interfaces 2017, 9, 17865–17871. (18) Xu, J. L.; Liu, Y. H.; Gao, X.; Sun, Y. L.; Shen, S.; Cai, X. L.; Chen, L. S.; Wang, S. D. Embedded Ag Grid Electrodes as Current Collector for Ultra-Flexible Transparent Solid-State Supercapacitor. ACS Appl. Mater. Interfaces 2017, 9, 27649–27656. (19) Li, N.; Huang, X. K.; Zhang, H. Y.; Shi, Z. C.; Wang, C. X. Graphene-Hollow-Cubes with Network-Faces Assembled 3D Micro-Structured Transparent and Free-Standing Film for High Performance Supercapacitor. J. Mater. Chem. A 2017, 5, 16803-16811. (20) Chen, T.; Xue, Y. H.; Roy, A. K.; Dai, L. M. Transparent and Stretchable HighPerformance Supercapacitors Based on Wrinkled Graphene Electrodes. ACS Nano 2014, 8, 1039-1046. (21) Na, L.; Huang, X. K.; Zhang, H. Y.; Li, Y. Y.; Wang, C. X. Transparent and SelfSupporting Graphene Films with Wrinkled-Graphene-Wall-Assembled Opening Polyhedron Building Blocks for High Performance Flexible/Transparent Supercapacitors. ACS Appl. Mater. Interfaces 2017, 9, 9763-9771. (22) Jo, K.; Lee, S.; Kim, S. M.; In, J. B.; Lee, S. M.; Kim, J. H.; Lee, H. J.; Kim, K. S. Stacked Bilayer Graphene and Redox-Active Interlayer for Transparent and Flexible High-Performance Supercapacitors. Chem. Mater. 2015, 27, 3621-3627. (23) Li, N.; Yang, G. Z.; Sun, Y.; Song, H. W.; Cui, H.; Yang, G. W.; Wang, C. X. FreeStanding and Transparent Graphene Membrane of Polyhedron Box-Shaped Basic Building Units Directly Grown Using a NaCl Template for Flexible Transparent and Stretchable Solid-State Supercapacitors. Nano Lett. 2015, 15, 3195-3203. (24) Gao, K. Z.; Shao, Z. Q.; Wu, X.; Wang, X.; Zhang, Y. H.; Wang, W. J.; Wang, F. J. PaperBased Transparent Flexible Thin Film Supercapacitors. Nanoscale 2013, 5, 5307-5311. (25) Liu, Y. H.; Xu, J. L.; Gao, X.; Sun, Y. L.; Lv, J. J.; Shen, S.; Chen, L. S.; Wang, S. D. Freestanding Transparent Metallic Network Based Ultrathin, Foldable and Designable Supercapacitors. Energy Environ. Sci. 2017, 10, 2534-2543.


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


(26) Kiruthika, S.; Sow, C.; Kulkarni, G. U. Transparent and Flexible Supercapacitors with Networked Electrodes. Small 2017, 13, 1701906. (27) Qiu, T. F.; Luo, B.; Giersig, M.; Akinoglu, E. M.; Hao, L.; Wang, X. J.; Shi, L.; Jin, M. H.; Zhi, L. J. Au@MnO2 Core-Shell Nanomesh Electrodes for Transparent Flexible Supercapacitors. Small 2014, 10, 4136-4141. (28) Gong, S., Zhao, Y. M., Shi, Q. Q., Wang, Y., Yap, L. W., Cheng, W. L. Self-Assembled Ultrathin Gold Nanowires as Highly Transparent, Conductive and Stretchable Supercapacitor. Electroanalysis 2016, 28, 1298-1304. (29) Lee H., Hong S., Lee J., Suh Y. D., Kwon J., Moon H., Kim H., Yeo J., Ko S. H. Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability. ACS Appl. Mater. Interfaces 2016, 8, 15449-15458. (30) Zhu, G. Y.; He, Z.; Chen, J.; Zhao, J.; Feng, X. M.; Ma, Y. W.; Fan, Q. L.; Wang, L. H.; Huang, W. Highly Conductive Three-Dimensional MnO2-Carbon Nanotube-Graphene-Ni Hybrid Foam as a Binder-Free Supercapacitor Electrode. Nanoscale 2014, 6, 1079-1085. (31) Song, J.; Li, H. H.; Li, S. Z.; Zhu, H. L.; Ge, Y.; Wang, S.; Feng, X. M.; Liu, Y. G. Electrochemical Synthesis of MnO2 Porous Nanowires for Flexible All-Solid-State Supercapacitor. New J. Chem. 2017, 41, 3750-3757. (32) Kang, Q.; Zhao, J.; Li, X.; Zhu, G. Y.; Feng, X. M.; Ma, Y. W.; Huang, W.; Liu, J. A Single Wire as All-Inclusive Fully Functional Supercapacitor. Nano Energy 2017, 32, 201-208. (33) Ma, H. Y.; Kong, D. B.; Xu, Y.; Xie, X. Y.; Tao, Y.; Xiao, Z. C.; Lv, W.; Jang, H. D.; Huang, J. X.; Yang, Q. H. Disassembly-Reassembly Approach to RuO2/Graphene Composites for Ultrahigh Volumetric Capacitance Supercapacitor. Small 2017, 13, 1701026. (34) Xiang, K.; Xu, Z. C.; Qu, T. T.; Tian, Z. F.; Zhang, Y.; Wang, Y. Z.; Xie, M. J.; Guo, X. K.; Ding, W. P.; Guo, X. F. Two Dimensional Oxygen-Vacancy-Rich Co3O4 Nanosheets with Excellent Supercapacitor Performances. Chem. Commun. 2017, 53, 12410-12413. (35) Liu, L. L.; Niu, Z. Q.; Chen, J. Unconventional Supercapacitors from Nanocarbon-Based Electrode Materials to Device Configurations. Chem. Soc. Rev. 2016, 45, 4340-4363. (36) Park, S.; Nam, I.; Kim, G. P.; Han, J. W.; Yi, J. Hybrid MnO2 Film with Agarose Gel for Enhancing the Structural Integrity of Thin Film Supercapacitor Electrodes. ACS Appl. Mater. Interfaces 2013, 5, 9908-9912.


19


Page 20 of 22

(37) Zhou, W. X.; Chen, J.; Li, Y.; Wang, D. B.; Chen, J. Y.; Feng, X. M.; Huang, Z. D.; Liu, R. Q.; Lin, X. J.; Zhang, H. M.; Mi, B. X.; Ma, Y. W. Copper Mesh Templated by Breath-Figure Polymer Films as Flexible Transparent Electrodes for Organic Photovoltaic Devices. ACS Appl. Mater. Interfaces 2016, 8, 11122-11127. (38) Wan, L. S.; Zhu, L. W.; Ou, Y.; Xu, Z. K. Multiple Interfaces in Self-Assembled Breath Figures. Chem. Commun. 2014, 50, 4024-4039. (39) Li, Z. G.; Ma, X. Y.; Zang, D. Y.; Hong, Q.; Guan, X. H. Honeycomb Porous Films of Pentablock Copolymer on Liquid Substrates via Breath Figure Method and Their Hydrophobic Properties with Static and Dynamic Behaviour. RSC Adv. 2015, 5, 21084-21089. (40) Daly, R.; Sader, J. E.; Boland, J. J. Taming Self-Organization Dynamics to Dramatically Control Porous Architectures. ACS Nano 2016, 10, 3087-3092. (41) Rafique, A.; Massa, A.; Fontana, M.; Bianco, S.; Chiodoni, A.; Pirri, C. F.; Hernández, S.; Lamberti, A. Highly Uniform Anodically Deposited Film of MnO2 Nanoflakes on Carbon Fibers for Flexible and Wearable Fiber-Shaped Supercapacitors. ACS Appl. Mater. Interfaces 2017, 9, 28386-28393. (42) Qiao, Z. S.; Yang, X. P.; Yang, S. H.; Zhang, L. Q.; Cao, B. Q. 3D Hierarchical MnO2 Nanorod/Welded Ag-Nanowire-Network Composites for High-Performance Supercapacitor Electrodes. Chem. Commun. 2016, 52, 7998-8001. (43) Chen, P.; Gu, L.; Xue, X. D.; Li, M. J.; Cao, X. B. Engineering the Growth of TiO2 Nanotube Arrays on Flexible Carbon Fibre Sheets. Chem. Commun. 2010, 46, 5906-5908. (44) Liu, L. Y.; Sun, Y. H.; Li, W. B.; Zhang, J. J.; Huang, X.; Chen, Z. J.; Sun, Y. M.; Di, C. A.; Xu, W.; Zhu, D. B. Flexible Unipolar Thermoelectric Devices Based on Patterned Poly[Kx(NiEthylenetetrathiolate)] Thin Films. Mater. Chem. Front. 2017, 1, 2111-2116. (45) Gao, X. P.; Lu, F.; Dong, B.; Liu, Y. Z.; Gao, Y.; Zheng, L. Q. Facile Synthesis of Gold and Gold-Based Alloy Nanowire Networks Using Wormlike Micelles as Soft Templates. Chem. Commun. 2015, 51, 843-846. (46) Qu, Q., Zhang P., Wang B., Chen Y., Tian S., Wu Y., Holze R. Electrochemical Performance of MnO2 Nanorods in Neutral Aqueous Electrolytes as a Cathode for Asymmetric Supercapacitors. J. Phys. Chem. C 2009, 113. 14020-14027.


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(47) He Y., Chen W., Li X., Zhang Z., Fu J., Zhao C., Xie E. Freestanding Three-Dimensional Graphene/MnO2 Composite Networks as Ultralight and Flexible Supercapacitor Electrodes. ACS Nano 2013, 7, 174-182. (48) Lei Z., Shi F., Lu L. Incorporation of MnO2-Coated Carbon Nanotubes Between Graphene Sheets as Supercapacitor Electrode. ACS Appl. Mater. Interfaces 2012, 4, 1058−1064.


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Patterning Island-Like MnO2 Arrays by Breath Figure Templates for

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