Layered Assembly of Reduced Graphene Oxide and Vanadium Oxide

Subscriber access provided by - Access paid by the | UCSB Libraries

Layered Assembly of Reduced Graphene Oxide and Vanadium Oxide Heterostructure Supercapacitor Electrodes with Larger Surface Area for Efficient Energy Storage Performance Buddha Deka Boruah, Sukanta Nandi, and Abha Misra ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.7b00358 • Publication Date (Web): 16 Mar 2018 Downloaded from http://pubs.acs.org on March 17, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 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

ACS Applied Energy Materials

Layered Assembly of Reduced Graphene Oxide and Vanadium Oxide Heterostructure Supercapacitor Electrodes with Larger Surface Area for Efficient Energy Storage Performance

Buddha Deka Boruaha, Sukanta Nandia and Abha Misraa* a

Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore,

Karnataka, India 560012 *

Corresponding Author

*

Email: Abha Misra: [email protected]

1

ACS Paragon Plus Environment

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

Page 2 of 24

Abstract The architecture of a supercapacitor (SC) electrode plays a crucial role in defining the overall energy storage performance of the SC. Layer-by-layer assembly of reduced graphene oxide (rGO) and vanadium oxide (V2O5) (rGO/V2O5) based heterostructure is patterned in interdigitated electrodes (IDEs) deposited directly on a flexible conducting current collector for SC. IDE pattern offers efficient accessibility to the electrolyte ions and synergistic contribution for energy storage. As-fabricated solid-state flexible sandwich-type SC with IDEs displays an efficient energy storage performance than conventional solid-state flexible sandwich-type SC composed of rGO/V2O5 electrodes. Moreover, a solid-state flexible inplane micro-supercapacitor (MSC) is fabricated that offers much higher capacitance (24 mF/cm2 and 34.28 F/cm3) and energy density (3.3 μWh/cm2 and 4.7 mWh/cm3). Asfabricated flexible in-plane MSC displays a negligible capacitance loss of about 6.3% after 10,000 charge-discharge cycles and superior stability of energy storage performance towards mechanical deformation. Keywords: interdigitated electrodes; heterostructure material; synergistic effect; sandwichtype supercapacitors; in-plane micro-supercapacitor.

2


Page 3 of 24 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


1. Introduction Designing the supercapacitor (SC) electrodes is now been considered as a preferable approach to improve energy storage performance. Generally, during the fabrication of SC electrodes, the electrochemically active materials are directly grown on metal current collectors via chemical bath deposition, hydrothermal method, electrochemical deposition, etc.1-4 However, these techniques do not allow achieving electrodes over a large area. Thereby, to resolve this problem, recently, vacuum filtration process has been widely used for the fabrication of SC electrodes.5,6 The physical stacking of electrode material during the filtration process hinders the electrolyte ions accessibility and also enhances the contact resistance due to reduced electron transportation efficiency. Müllen’s group introduced spray deposition to fabricate in-plane micro-supercapacitor (MSC) on flexible substrate.7 Also, Boruah et al reported flexible sandwich-type asymmetric tandem SC via the spray deposition.8 However, the main drawback associated with spray deposition is the inaccessibility of the inner portion of the electrode material coated on a current collector and known as dead material to the electrolyte ions and electrons. Therefore, the challenge lies in exposing larger surface area of the electrode material effectively on the current collector. Herein, for the first time, we present the patterning of interdigitated electrodes (IDEs) composed of heterostructure material for high-performance SC application. Layer-by-layer deposition of reduced graphene oxide (rGO) and vanadium oxide (V2O5) (rGO/V2O5) on flexible metal current collector in the form of IDEs for SC. As-fabricated solid-state flexible sandwich-type porous SC (PSC), where two identical IDE patterns were used, displays much higher capacitance as compared to solid-state flexible sandwich-type conventional SC (CSC) composed of identical conventional rGO/V2O5 electrodes. The electrochemical response of IDE patterns composed of rGO/V2O5 heterostructure was further studied by fabricating a 3



Page 4 of 24

solid-state flexible in-plane micro-supercapacitor (MSC). In-plane MSC shows much higher values of capacitance (24 mF/cm2 and 34.28 F/cm3) and energy density (3.3 μWh/cm2 and 4.7 mWh/cm3). Stable energy storage performance towards mechanical deformation and negligible capacitance loss (6.3%) after 10,000 charge-discharge (CD) cycles were also recorded for the solid-state flexible in-plane MSC. Therefore, results suggest that the interdigitated type heterostructure electrode composed of rGO/V2O5 is a potential candidate for efficient energy storage performance for SC application. 2. Results and Discussion Figure 1a shows the schematic illustration of fabrication patterned electrode (IDEs) for SC composed of sequential layer-by-layer pattern of rGO and V2O5. The detailed fabrication process of IDEs is mentioned in the experimental section. The main advantage associated with mask-assisted spray deposition technique is large area deposition of electrode material over any type of conducting substrate. Figure 1b shows the patterned electrodes on various conducting flexible substrates such as gold/polyethylene terephthalate (Au/PET), copper (Cu), indium tin oxide (ITO)/PET, stainless steel (SS), aluminium (Al) and nickel (Ni), respectively. Figure 1c shows the schematic diagram of the sandwich-type CSC and below schematic represents the charge storage mechanism under charging condition. In sandwichtype CSC, some of the electrode materials near or attached to the current collector are not favourable for electrolyte ions. In addition, the highly packed electrode material in sandwichtype CSC introduces the longer ions diffusion pathways during electrolytic process. However, these issues can be resolved by direct patterning of electrode material on current collector. Figure 1d depicts the schematic representation of the sandwich-type PSC, whereas the charge storage mechanism under charging state is shown in the below schematic. The patterned electrode allows the favourable path for electrolyte ions to interact with the surfaces 4


Page 5 of 24 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


of rGO and V2O5 sheets. As a result, the charge storage capacity would enhance in the PSC as compared to the CSC.

a

rGO

c

Current collector Electrode material PVA/H3PO4

V2O5 rGO rGO

× V2O5

×

V2O5

Electrolyte ions

×

V2O5 rGO V2O5 rGO

×

d

Current collector

b

PVA/H3PO4 Au/PET

SS

e

Cu

ITO/PET

Al

Ni

g

f

h 1 μm

5 µm

1 µm

Figure 1. (a) Schematic illustration of the fabrication of flexible PSC electrode. (b) Asfabricated PSC electrodes on various conducting flexible substrates such as Au/PET, Cu, ITO/PET, SS, Al and Ni. (c) and (d) are the schematic diagrams of CSC and PSC, where below schematics represent the charge storage mechanisms under charging condition. (e) and (f) are the SEM images of rGO and V2O5. Raman spectra of (g) rGO and (h) V2O5.

5



Page 6 of 24

Microstructures of rGO and V2O5 were examined by the scanning electron microscopy (SEM), where Figure 1e shows the SEM image of rGO sheets. Figure 1f shows the SEM image of V2O5, where inset depicts the randomly oriented V2O5 microstructures. Raman analysis of the samples were recorded, where the observed major peaks at around 1352 cm-1 and 1600 cm-1 in rGO (Figure 1g) correspond to D and G bands. The intensity ratio of ID/IG for rGO is found to be 1.083, which is larger than graphene oxide (GO) (Figure S1). The increase in ID/IG of rGO as compared to GO is mainly due to the generation of more structural defects under the reduction process.9,10 Figure 1h shows the Raman spectrum of V2O5, where the observed high intensity peak at around 142 cm-1 corresponds to V-O-V bonds vibration of orthorhombic phase. The observed other peaks of relatively lesser intensity at around 282 and 405 cm-1 are the vibrations of V-Ob-V and V-Oc bonds.11 Moreover, the X-ray diffraction (XRD) of V2O5 is shown in Figure S2. The observed diffraction peaks at around 2θ = 27.8, 37 and 42.2o, respectively correspond to the diffraction planes of (110), (401), and (002) denote the orthogonal symmetry (space group: Pmmn, a = 1.1516, b = 0.3566, c = 0.4372 nm) crystal structure of as-synthesized V2O5.12 The electrochemical responses of the as-fabricated solid-state flexible sandwich-type SCs were measured in solid-state PVA/H3PO4 electrolyte. During the fabrication of solidstate flexible sandwich-type CSC and PSC, flexible SS was used as a current collector. Figure 2a shows the cyclic voltammetry (CV) comparison of CSC and PSC at a scan rate of 100 mV/s. It is observed from the result that the area under the CV of the sandwich-type PSC is significantly enhanced (57%) as compared to sandwich-type CSC. Also, the CV comparison of CSC and PSC in terms of mass is provided in the supporting information (Figure S3). The increase in energy storage performance of the PSC as compared to the CSC is mainly due to the more accessibility of electrolyte ions in IDE configuration (Figure 1d). 6


Page 7 of 24 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


In IDEs pattern, rGO offers EDLC response and V2O5 offers the pseudocapacitance to introduce the synergistic response under energy storage.13,14 To study the contribution of energy storage response originated from V2O5 in the rGO/V2O5 electrode, the CV measurement of pristine rGO was also studied by fabricating sandwich-type CSC composed of pristine rGO electrodes. Figure S4 shows the CV comparison of pristine rGO based CSC and rGO/V2O5 based CSC. Likewise, the notable increase in the area under the CV in rGO/V2O5 as compared to pristine rGO is observed due to the synergistic response in rGO/V2O5. Also, the layer-by-layer patterning of rGO and V2O5 in the PSC offers efficient energy storage performance than the randomly mixed of rGO and V2O5 (rGO_V2O5) due to significant synergistic effect.5,15 Figure S5 depicts the CV comparison of sandwich-type CSCs composed of rGO/V2O5 and rGO_V2O5 symmetric electrodes. Figure 2b and c show the CV profiles of CSC and PSC at different scan rates of 100 to 1000 mV/s, whereas, the CV responses of the CSC and the PSC at relatively lower scan rates of 5 to 50 mV/s were provided in the supporting information (Figure S6a and b). The identical CV profiles of both the CSC and the PSC from lower to higher scan rate reveal stable energy storage performance based SCs. Likewise, the increase in the area under CV of the PSC as compared to CSC at every scan rate suggests the enhancement of energy storage capacity. The stability of energy storage responses of the flexible sandwich-type CSC and PSC were further studied under various bending angles as shown in Figure S7a and b. The negligible deviation in the area under CV responses at different bending configurations as compared to original configuration of both the CSC and the PSC suggest the stable energy storage responses based flexible SCs. Figure 2d and e show CD profiles of the CSC and the PSC at different current densities over the working voltage of 1 V. The variation of areal capacitance with respect to the current 7



Page 8 of 24

density of the CSC and the PSC is depicted in Figure 2f. The decrease in the specific capacitances with increase in the current density is mainly due to the ideal energy storage performances of the CSC and the PSC.

a

b

c

d

e

f

g

h

i

Figure 2. (a) CV comparison of flexible sandwich-type CSC and PSC at a scan rate of 100 mV/s over the working voltage of 1 V. (b) and (c) are the CV profiles of the CSC and the PSC at different scan rates of 100 to 1000 mV/s. CD responses of (d) CSC and (e) PSC at different current densities. (f) Areal capacitance comparison plot with respect to the current density of the CSC and the PSC. (g) A comparison for Ragone plots of the CSC and the PSC. (h) Capacitance retention comparison plot of CSC and PSC for 5000 CD cycles. (i) Nyquist plots of CSC and PSC.

8


Page 9 of 24 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


Notable increase in the areal capacitance of the PSC as compared to the CSC is measured at every current density, where, at a current density of 0.222 mA/cm2, the observed areal capacitance for the CSC was found to be 1.13 mF/cm2 (electrode capacitance is 4.52 mF/cm2), which increased to 2.47 mF/cm2 (electrode capacitance is 9.88 mF/cm2) in PCS. These values are higher than the previously reported flexible sandwich-type solid-state SCs, e.g., 0.442 mF/cm2 at 0.01 mA/cm2 for SnSe nanosheets,16 0.394 mF/cm2 at 281 nA/cm2 for graphene,17 0.186 mF/cm2 at 0.001 mA/cm2 for GeSe2 nanostructure,18 0.4 mF/cm2 at 0.002 mA/cm2 for SnSe nanodisks,16 etc. Figure S8 depicts the volumetric capacitance comparison plot of the CSC and the PSC. The calculated volumetric capacitance of the CSC was found to be 1.62 F/cm3 (electrode capacitance is 6.46 F/cm3), which is increased to 3.52 F/cm3 (electrode capacitance is 14.11 F/cm3) in the PSC at the current density of 0.32 A/cm3. Moreover, the observed volumetric capacitances of the PSC at the current densities of 0.105, 0.16 and 0.21 A/cm3, respectively were measured to be 8.53, 5.91 and 4.7 F/cm3. Also, the calculated specific capacitance of the PSC was found to be 4000 mF/g where the electrode capacitance is equal to 16000 mF/g at 0.05 A/g. These values are higher than previously reported solid-state SCs.19-22 Figure 2g shows the comparison Ragone plot for both the CSC and the PSC. The calculated areal (volumetric) energy density and the areal (volumetric) power density for the CSC were measured to be 0.157 µWh/cm2 (0.225 mWh/cm3) and 111 µW/cm2 (158.57 mW/cm3) at 0.222 mA/cm2, which are enhanced to 0.342 µWh/cm2 (0.489 mWh/cm3) and 111 µW/cm2 (158.57 mW/cm3), respectively in the PSC. Figure S9 depicts the volumetric power density versus volumetric energy density plot of CSC and PSC. In addition, the capacitance stability of the CSC and the PSC were studied for 5000 CD cycles over a working voltage of 1 V (Figure 2h). Negligible capacitance losses of 3.9% in CSC and 5.7% 9



Page 10 of 24

in PSC were obtained after 5000 CD cycles as compared to the first CD cycle. To further evaluate the electrochemical performances of the CSC and PSC, the electrochemical impedance spectroscopy (EIS) were measured in a frequency range of 0.01–100 kHz with an AC perturbation of 5 mV. Figure 2i shows the time-dependent EIS spectrum known as a Nyquist plot for both the CSC and the PSC and Figure S10 shows a magnified image in the high frequency range. As-fabricated solid-state flexible sandwich-type CSC and PSC exhibited equivalent series resistances (ESR) of 0.75 Ω and 0.5 Ω, respectively which demonstrates low resistance that includes contact resistance between the current collector and active electrode material, current collector resistance and solution resistance based solid-state flexible SCs. Furthermore, to explore the energy storage performance of the rGO/V2O5 IDEs patterned electrode, a solid-state flexible in-plane MSC was fabricated on flexible PET substrate. During the fabrication of solid-state flexible in-plane MSC, first metal current collectors of Au/Cr (200/25 nm) were deposited on flexible PET substrate via the IDEs patterned mask assisted sputtering process. Afterward, rGO and V2O5 were spray deposited on top of the current collectors and Figure S11 shows the schematic illustration of fabrication processes involved in MSC. Figure 3a depicts the schematic illustration of the as-fabricated solid-state flexible in-plane MSC, where the electrochemical responses of the MSC was then evaluated in PVA/H3PO4 electrolyte and below schematic depicts the charge storage mechanism. Figure 3b and c show the CV profiles of the in-plane MSC at different scan rates of (5 – 50 mV/s) and (100 – 1000 mV/s), respectively. Identical CV variation from lower (5 mV/s) to much higher (1000 mV/s) scan rate of the MSC illustrates stable capacitive response. Figure 3d shows the comparative analysis of areal capacitance of the MSC with previously reported solid-state MSCs. Obviously, higher values of areal capacitances were 10


Page 11 of 24 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


measured due to the synergistic response as mentioned earlier. These values are much higher than previously reported solid-state MSCs, for examples 0.0807 mF/cm2 at 10 mV/s for methane plasma reduced rGO based MSC,23 0.51 mF/cm2 at 20 mV/s for laser reduced rGO based MSC,24 1.08 mF/cm2 at 10 mV/s for exfoliated graphene and PEDOT:PSS based MSC,7 2.1 mF/cm2 at 1 mV/s for activated carbon based MSC,25 etc. The higher values of the areal capacitance of the MSC implying efficient energy storage performance based solid-state MSC. Figure S12 shows the volumetric capacitance plot with respect to scan rate of the MSC.

a

b : Au

c

: PET

e

d

f This work

This work

32 19 7 25 7 28

g

26 23

30 24

31 24

27

h

i

Figure 3. (a) Schematic illustration of the as-fabricated solid-state flexible in-plane MSC and below schematic charge storage mechanism. CV profiles of the flexible in-plane MSC at 11



Page 12 of 24

different scan rates of (b) 5 – 50 mV/s and (c) 100 – 1000 mV/s at a working voltage of 1 V. (d) Comparative study of areal capacitance of the solid-state flexible in-plane MSC with previously reported solid-state MSCs. (e) CD profiles of the MSC at different currents. (f) Ragone plot demonstrating the comparisons of areal energy density and power density of the MSC with previously reported solid-state MSCs. (g) Capacitance retention for 10,000 CD cycles. (h) Nyquist plot and inset shows the magnified image in the high frequency range. (i) Impedance phase angle plot with respect to frequency of the MSC. In order to study the stability of energy storage performance of the flexible MSC, the CV responses were measured at different bending angles. Figure S13a shows the digital photograph of the MSC at a bend angle of θ. The CV responses of the MSC at different bending angles (θ = 0o, 10o, 20o, 30o, 40o, 50o, 60o and 70o) are shown in Figure S13b. No significant deviation in the CV profile was measured for the MSC. Therefore, results reveal that as-fabricated MSC has superior stable energy storage performance towards mechanical deformations. Moreover, CD responses of the MSC were measured at different currents (0.05 – 1 mA) (Figure 3e). The symmetric charge and discharge profile of the MSC suggests efficient CD reversible response. The coulombic efficiency (= discharge time/charge time ×100%) and areal capacitance were measured at different current densities (Figure S14). The measured average coulombic efficiency of the MSC was found to be 92% suggesting better charge and discharge reversibility of the MSC. Likewise, the observed higher values of areal/volumetric capacitances range from 5.8 (8.29) to 7.3 mF/cm2 (10.43 F/cm3) demonstrate high performance based as-fabricated MSC. Furthermore, Figure S15 depicts the areal energy density with respect to the scan rate (1 – 100 mV/s) of the MSC. The measured areal/volumetric energy densities at 1 mV/s and 50 mV/s are found be 3.3 μWh/cm2 (4.7 mWh/cm3) and 1.7 μWh/cm2 (2.43 mWh/cm3), 12


Page 13 of 24 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


respectively which are much higher than reported MSCs. For examples, 0.074 μWh/cm2 for graphene quantum dots MSC,19 0.38 μWh/cm2 for 3D graphene pellet MSC,29 0.12 μWh/cm2 for rGO-Au MSC,30 0.012 μWh/cm2 for rGO MSC,31 0.05 μWh/cm2 for rGO/hydrated GO MSC,24 0.10 μWh/cm2 for RuO2/CNTs MSC,32 etc. Figure 3f shows the Ragone plot showing comparisons of areal energy density and power density of the MSC with previously reported solid-state MSCs. Moreover, the capacitance retention analysis of the MSC was studied for 10,000 CD cycles as shown in Figure 3g and Figure S16 shows few CD cycles. Only, 6.3% capacitance loss was noticed after 10,000 CD cycles as compared to the first CD cycle for the MSC. This value is much lower than reported MSCs, e.g., 16% capacitance loss after 2000 cycles for LiG-FeOOH//LiG-MnO2,33 27.5% capacitance loss after 1000 cycles for MnO2,34 4% capacitance loss after 1000 cycles for PANI nanowires,35 25.9% capacitance loss after a large 15000 cycles for MnOx/Au multilayer,36 6.5% capacitance loss after 5000 cycles for rGO,37 etc. Figure 3h shows the Nyquist plot of the MSC which shows a low ESR value equal to 4 Ω and inset depicts the magnified image in the high frequency range. The impedance phase angle with respect to the frequency plot known as Bode plot of the MSC is shown in Figure 3i. The measured high characteristic frequency for the MSC was found to be 3.067 Hz corresponds to the time constant is equal to 326 ms at a phase angle of -45o. High value of characteristic frequency suggests that as-fabricated MSC has an efficient ac line filtering capability. 3. Conclusion In conclusion, this work presents the fabrication of efficient IDEs patterned SC electrode composed of rGO/V2O5 heterostructure via mask assisted spray deposition for high performance SC applications. As-fabricated solid-state flexible sandwich-type PSC displays 13



Page 14 of 24

efficient energy storage performance (57% enhancement) as compared to solid-state flexible sandwich-type CSC. The synergistic response originated from rGO and V2O5 offered much efficient energy storage capacity in PSC. Moreover, as-fabricated solid-state flexible in-plane MSC composed of rGO/V2O5 displayed efficient areal (volumetric) capacitance of 24 mF/cm2 (34.28 F/cm3) and energy density of 3.3 μWh/cm2 (4.7 mWh/cm3), respectively. Negligible capacitance loss of 6.3% after 10,000 CD cycles as compared to the first CD cycle is recorded for the MSC. In addition, as-fabricated solid-state flexible in-plane MSC showed outstanding stable electrochemical response towards the mechanical deformation. Therefore, the IDEs patterned electrode composed of rGO/V2O5 is a potential candidate for high performance energy storage device application. 4. Experimental Section Material synthesis: The GO was prepared by modified Hummers method.6 As prepared GO was then annealed in N2 gas of flow rate 200 standard cubic centimeter per minute (sccm) for 10 min at 250 oC to form rGO.8 The synthesis of V2O5 was as follows: 2 mmol of NH4VO3 was added into 30 ml distilled (DI) water and 2 ml ammonium hydroxide under vigorous stirring at room temperature. Then, 20 mmol C2H5NS was added into the above solution and then kept stirring another 2h. Afterward, the solution was maintained at 180 °C for 20 h. Finally, the V2O5 suspension was then cleaned with DI water and ethanol alternatively and dried at 60 °C for 2 h. Fabrication of solid-state sandwich-type PSC: Initially, 0.3 g V2O5 and 0.06 g rGO were separately dispersed into 100 ml of dimethylformamide solutions under ultrasonication process to form V2O5 and rGO inks. Then, SS substrate was cleaned with acetone, isopropyl 14


Page 15 of 24 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


alcohol, and DI water then dried with N2 gas. The cleaned SS was masked by IDEs patterned SS mask using adhesive heat resistive kapton tape. The rGO and V2O5 inks were spray deposited alternatively for four layers (3 ml of ink was used in each layer) at 180 °C using N2 gas as a carrier gas for 7 µm thickness (Figure S17). For the fabrication of solid-state sandwich-type CSC electrode, same amount of rGO and V2O5 inks were spray deposited on SS in absence of any IDEs patterned SS mask followed by the same procedures as mentioned above. During the fabrication of pristine rGO based CSC, directly 12 ml of rGO ink was spray deposited on the SS current collector. As-fabricated symmetric electrodes were then assembled with a filter paper used as separator in PVA/H3PO4 electrolyte. For the preparation of PVA/H3PO4 electrolyte, 4 g of PVA was dissolved into 40 mL of DI water at 95 °C under vigorous stirring for 30 min. Then, 8 ml of H3PO4 was added slowly under vigorous stirring for another 30 min. Afterward, the samples along with filter paper were dipped into the PVA/H3PO4 electrolyte for 10 min and thereafter assembled in symmetric configuration to form solid-state sandwichtype PSC. The assembled PSC was then kept overnight under laminar air flow chamber to form solid-state flexible PSC. Similar procedure was also followed during the fabrication of solid-state sandwich-type CSCs. Fabrication of solid-state flexible in-plane MSC: Initially, cleaned PET substrate was fixed with the IDEs patterned SS mask using the heat resistive kapton tape. Then, Au/Cr (200/25 nm) electrode was deposited via sputtering process. Afterward, the rGO/V2O5 were deposited using spray deposition technique on top of Au/Cr current collectors as mentioned above. The gap between IDEs is 700 µm. Finally, PVA/H3PO4 electrolyte was drop-casted on the active areas of in-plane MSC and then kept overnight under laminar airflow chamber. The total active area of the MSC was 1.5 x 1.3 cm2. 15



Page 16 of 24

Electrochemical measurements: The electrochemical responses of the SCs were investigated by CV, CD and EIS measurements using CHI660E electrochemical workstation. CV responses were measured with different scan rates and working voltages. Likewise, CD responses of the SCs were performed in different working voltages and current densities. Furthermore, EIS measurements were evaluated in the frequency ranging from 0.01 Hz to 100 kHz with a potential amplitude of 5 mV. Calculation: The capacitance ( Cdevice ) of the SC was calculated from CV plots followed the relation, Vf

Cdevice

1  I (V )dV  (V f  Vi ) Vi

where,  is the scan rate (V/s), Vi and V f are the initial and final voltage limit of the CV plot,

I (V ) is the discharge current (A). The areal capacitance ( C A , mF/cm2) and specific ( C g , F/g) capacitance were calculated according to the relations,

CA 

Cdevice A

and Cg 

Cdevice M

where, A and M are the area (cm2) and total mass (g) of electrode material. Similarly, the areal capacitance ( C A , mF/cm2) and specific ( C g , F/g) capacitance were calculated from the CD curves using the relations,

CA 

I t AV 16


Page 17 of 24 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


and It MV

Cg 

where, I is the applied current (A), t is the discharge time (s) and V is the applied voltage (V).38 The specific areal E A (Wh/cm2) and gravimetric Eg (Wh/kg) energy densities were calculated by using the relations, 1 ( V ) 2 EA   CA  2 3600

And 1 (V ) 2 Eg   Cg  2 3.6

The specific areal PA (W/cm2) and gravimetric Pg (W/kg) power densities were obtained by the relations,

PA 

EA  3600 t

And

Pg 

Eg t

 3600

Supporting Information: Raman spectrum of GO; XRD pattern of V2O5; Comparison CV of CSC and PSC; CV of rGO/V2O5 CSC and pristine rGO CSC; CV comparison of rGO/V2O5 based CSC and rGO_V2O5 based CSC; CV responses of CSC and PSC at different scan rates of 5 to 50 mV/s; CV responses of the CSC and PSC at different bending angles; Volumetric 17



Page 18 of 24

capacitance plots of CSC and PSC; Ragone plots of CSC and PSC; Nyquist plots of the CSC and the PSC in the high frequency range; Schematic illustration the fabrication of flexible inplane MSC; Volumetric capacitance plot of the in-plane MSC; Digital photograph of the MSC at a bend angle of θ; CV of the MSC at different bending angles; Coulombic efficiency and areal capacitance plots of the MSC; Areal energy density of the MSC with respect to scan rate and cross-sectional SEM image of PSC electrode. Acknowledgements AM would like to thank the Department of Science and Technology (DST) for funding the project under the fast track grant (Grant no. DST-1272). 5. References 1. Alhaebshi, N.; Rakhi, A. R. B.; Alshareef, H. N. Conformal Coating of Ni(OH)2 Nanoflakes on Carbon Fibers by Chemical Bath Deposition for Efficient Supercapacitor Electrodes. J. Mater. Chem. A 2013, 1, 14897–14903. 2. Boruah, B. D.; Maji, A.; Misra, A. Synergistic Effect in the Heterostructure of ZnCo2O4 and Hydrogenated Zinc Oxide Nanorods for High Capacitive Response. Nanoscale 2017, 9, 9411–9420. 3. Duay, J.; Sherrill, S. A.; Gui, Z.; Gillette, E.; Lee, S. B. Self-Limiting Electrodeposition of Hierarchical MnO2 and M(OH)2/MnO2 Nanofibril/Nanowires: Mechanism and Supercapacitor Properties. ACS Nano 2013, 7, 1200–1214. 4. Boruah, B. D.; Misra, A. Nickel Hydroxide Coated Carbon Nanoparticles Mediated Hybrid Three-dimensional Graphene Foam Assembly for Supercapacitor. RSC Adv. 2016, 6, 36307–36313.

18


Page 19 of 24 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


5. Zhao, M. – Q.; Ren, C. E.; Ling, Z.; Lukatskaya, M. R.; Zhang, C.; Aken, K. L. V.; Barsoum, M. W.; Gogotsi, Y. Flexible MXene/Carbon Nanotube Composite Paper with High Volumetric Capacitance. Adv. Mater. 2015, 27, 339–345. 6. Boruah, B. D.; Misra, A. Polyethylenimine Mediated Reduced Graphene Oxide Based Flexible Paper for Supercapacitor. Energy Storage Materials 2016, 5, 103–110. 7.

Liu, Z.; Wu, Z. –S.; Yang, S.; Dong, R., Feng, X.; Müllen, K. Ultraflexible In‐Plane Micro‐Supercapacitors by Direct Printing of Solution‐Processable Electrochemically Exfoliated Graphene. Adv. Mater. 2016, 28, 2217–2222.

8. Boruah, B. D.; Misra, A. Internal Asymmetric Tandem Supercapacitor for High Working Voltage along with Superior Rate Performance. ACS Energy Lett. 2017, 2, 1720–1728. 9. Moon, I. K.; Lee, J.; Ruoff, R. S.; Lee, H. Reduced Graphene Oxide by Chemical Graphitization. Nat. commun. 2010, 1, 73–78. 10. Das, A. K.; Srivastav, M.; Layek, R. K.; Uddin, M. E.; Jung, D.; Kim, N. H.; Lee, J. H. Iodide-mediated Room Temperature Reduction of Graphene Oxide: A Rapid Chemical Route for the Synthesis of a Bifunctional Electrocatalyst. J. Mater. Chem. A 2014, 2, 1332–1340. 11. Abd-Alghafour, N. M.; Ahmed, N. M.; Hassanc, Z. Fabrication and Characterization of V2O5 Nanorods based Metal–semiconductor–metal Photodetector. Sens. Actuators A 2016, 250, 250–257.

19



Page 20 of 24

12. Pan, A.; Zhang, J. –G.; Nie, Z.; Cao, G.; Arey, B. W.; Li, G.; Liang, S. –Q.; Liu, J. Facile Synthesized Nanorod Structured Vanadium Pentoxide for High-rate Lithium Batteries. J. Mater. Chem. 2010, 20, 9193–9199. 13. Beidaghi, M.; Gogotsi, Y. Capacitive Energy Storage in Micro-scale Devices: Recent Advances in Design and Fabrication of Micro-supercapacitors. Energy Environ. Sci. 2014, 7, 867–884. 14. Chen, Z.; Augustyn, V.; Wen, J.; Zhang, Y.; Shen, M.; Dunn, B.; Lu, Y. HighPerformance

Supercapacitors

Based

on

Intertwined

CNT/V2O5

Nanowire

Nanocomposites. Adv. Mater. 2011, 23, 791–795. 15. Tang, C.; Zhang, Q.; Zhao, M. –Q.; Huang, J. –Q.; Cheng, X. –B.; Tian, G. –L.; Peng, H. –J.; Wei, F. Nitrogen-Doped Aligned Carbon Nanotube/Graphene Sandwiches: Facile Catalytic Growth on Bifunctional Natural Catalysts and Their Applications as Scaffolds for High-Rate Lithium-Sulfur Batteries. Adv. Mater. 2014, 26, 6100 – 6105. 16. Zhang, C.; Yin, H.; Han, M.; Dai, Z.; Pang, H.; Zheng, Y.; Lan, Y. –Q.; Bao, J.; Zhu, J. Two-Dimensional Tin Selenide Nanostructures for Flexible All-Solid-State Supercapacitors. ACS Nano 2014, 8, 3761 – 3770. 17. Yoo, J. J.; Balakrishnan, K.; Huang, J.; Meunier, V.; Sumpter, B. G.; Srivastava, A.; Conway, M.; Reddy, A. L. M.; Yu, J.; Vajtai, R.; Ajayan, P. M. Ultrathin Planar Graphene Supercapacitors. Nano Lett. 2011, 11, 1423–1427. 18. Wang, X.; Liu, B.; Wang, Q.; Song, W.; Hou, X.; Chen, D.; Cheng, Y.; Shen, G. Three-Dimensional Hierarchical GeSe2 Nanostructures for High Performance Flexible All-Solid-State Supercapacitors. Adv. Mater. 2013, 25, 1479 –1486.

20


Page 21 of 24 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


19. Liu, W. –W.; Feng, Y. –Q.; Yan, X. –B.; Chen, J. –T.; Xue, Q. –J. Superior MicroSupercapacitors Based on Graphene Quantum Dots. Adv. Funct. Mater. 2013, 23, 4111–4122. 20. Bae, J.; Park, Y. J.; Lee, M.; Cha, S. N.; Choi, Y. J.; Lee, C. S.; Kim, J. M.; Wang, Z. L. Single-Fiber-Based Hybridization of Energy Converters and Storage Units Using Graphene as Electrodes. Adv. Mater. 2011, 23, 3446–3449. 21. Bae, J.; Song, M. K.; Park, Y. J.; Kim, J. M.; Liu, M.; Wang, Z. L. Fiber Supercapacitors Made of Nanowire‐Fiber Hybrid Structures for Wearable/Flexible Energy Storage. Angew. Chem. 2011, 50, 1683–1687. 22. Li, Y.; Sheng, K.; Yuan, W.; Shi, G. A High-performance Flexible Fibre-shaped Electrochemical Capacitor Based on Electrochemically Reduced Graphene Oxide. Chem. Commun. 2013, 49, 291–293. 23. Wu, Z. –S.; Parvez, K.; Feng, X.; Müllen, K. Graphene-based In-plane Microsupercapacitors with High Power and Energy Densities. Nat. commun. 2013, 4, 2487– 2494. 24. Gao, W.; Singh, N.; Song, L.; Liu, Z.; Reddy, A. L. M.; Ci, L.; Vajtai, R.; Zhang, Q.; Wei, B.; Ajayan, P. M. Direct Laser Writing of Micro-supercapacitors on Hydrated Graphite Oxide Films. Nat. Nanotechnol. 2011, 6, 496–500. 25. Pech, D.; Brunet, M.; Taberna, P. –L.; Simon, P.; Fabre, N.; Mesnilgrente, F.; Conédéra, V.; Durou, H. Elaboration of a Microstructured Inkjet-printed Carbon Electrochemical Capacitor. J. Power Sources 2010, 195, 1266–1269.

21



Page 22 of 24

26. Beidaghi, M.; Wang, C. Micro-Supercapacitors Based on Interdigital Electrodes of Reduced Graphene Oxide and Carbon Nanotube Composites with Ultra High Power Handling Performance. Adv. Funct. Mater. 2012, 22, 4501–4510. 27. Hsia, B.; Marschewski, J.; Wang, S.; In, J. B.; Carraro, C.; Poulikakos, D.; Grigoropoulos,

C.

P.;

Maboudian,

R.

Highly

Flexible,

All

Solidstate

Microsupercapacitors from Vertically Aligned Carbon Nanotubes. Nanotechnology 2014, 25, 055401–055409. 28. Wang, S.; Hsia, B.; Carraroa, C.; Maboudian, R. High-performance All Solid-state Microsupercapacitor Based on Patterned Photoresistderived Porous Carbon Electrodes and an Ionogel Electrolyte. J. Mater. Chem. A 2014, 2, 7997–8002. 29. Zhang, L.; Armond, D. D.; Alvarez, N. T.; Malik, R.; Oslin, N.; McConnell, C.; Adusei, P. K.; Hsieh, Y. –Y.; Shanov, V. Flexible Micro-Supercapacitor Based on Graphene with 3D Structure. Small 2017, 13, 1603114–603123. 30. Li, R. –Z.; Peng, R.; Kihm, K. D.; Bai, S.; Bridges, D.; Tumuluri, U.; Wu, Z.; Zhang, T.; Compagnini, G.; Fengf, Z.; Hu, A. High-rate In-plane Micro-supercapacitors Scribed onto Photo Paper using In Situ Femtolaser-reduced Graphene Oxide/Au Nanoparticle Microelectrodes. Energy Environ. Sci. 2016, 9, 1458–1467. 31. Yoo, J. J.; Balakrishnan, K.; Huang, J.; Meunier, V.; Sumpter, B. G.; Srivastava, A.; Conway, M.; Reddy, A. L. M.; Yu, J.; Vajtai, R.; Ajayan, P. M. Ultrathin Planar Graphene Supercapacitors. Nano Lett. 2011, 11, 1423–1427. 32. Wang, X.; Yin, Y.; Hao, C.; You, Z. A High-performance Three-dimensional Micro supercapacitor Based on Ripple-like Ruthenium Oxide–Carbon Nanotube Composite Films. Carbon 2015, 82, 436–445. 22


Page 23 of 24 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


33. Li, L.; Zhang, J.; Peng, Z.; Li, Y.; Gao, C.; Ji, Y.; Ye, R.; Kim, N. D.; Zhong, Q.; Yang, Y.; Fei, H.; Ruan, G.; Tour, J. M. High‐Performance Pseudocapacitive Microsupercapacitors from Laser‐Induced Graphene. Adv. Mater. 2016, 28, 838–845. 34. Wang, X.; Myers, B. D.; Yan, J.; Shekhawat, G.; Dravid, V.; Lee, P. S. Manganese Oxide Micro-supercapacitors with Ultra-high Areal Capacitance. Nanoscale 2013, 5, 4119–4122. 35. Wang, K.; Zou, W.; Quan, B.; Yu, A.; Wu, H.; Jiang, P.; Wei, Z. An All-Solid-State Flexible Micro-supercapacitor on a Chip. Adv. Energy Mater. 2011, 1, 1068–1072. 36. Si, W.; Yan,C.; Chen, Y.; Oswald, S.; Han, L.; Schmidt, O. G. On Chip, All Solidstate and Flexible Micro-supercapacitors with High Performance Based on MnOx/Au Multilayers. Energy Environ. Sci. 2013, 6, 3218–3223. 37. Wu, Z. – K.; Lin, Z.; Li, L.; Song, B.; Moon, K. – S; Bai, S. – L.; Wong, C. – P. Flexible Micro-supercapacitor Based on In-situ Assembled Graphene on Metal Template at Room Temperature. Nano Energy 2014, 10, 222–228. 38. Boruah, B. D.; Misra, A. A Flexible Ternary Oxide Based Solid-state Supercapacitor with Excellent Rate Capability. J. Mater. Chem. A 2016, 4, 17552–17559.

23



Page 24 of 24

TOC:

CSC

××

×× ××

××

PSC

24


Layered Assembly of Reduced Graphene Oxide and Vanadium Oxide

Recommend Documents