Synthesis of Ag Anchored Ag3VO4 Stacked Nanosheets: Toward a

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Synthesis of Ag Anchored AgVO Stacked Nanosheets: Towards a Negative Electrode Material for High Performance Asymmetric Supercapacitor Devices Sadayappan Nagamuthu, Subbukalai Vijayakumar, and Kwang-Sun Ryu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b04925 • Publication Date (Web): 16 Aug 2016 Downloaded from http://pubs.acs.org on August 17, 2016

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The Journal of Physical Chemistry

Synthesis of Ag Anchored Ag3VO4 Stacked Nanosheets: Towards a Negative Electrode Material for High Performance Asymmetric Supercapacitor Devices Sadayappan Nagamuthu, Subbukalai Vijayakumar, and Kwang-Sun Ryu* Department of Chemistry, University of Ulsan, Muger-dong, Nam-gu, Ulsan 680-749, Republic of Korea ---------------------------------------------------------------------------------------------------------------------

Abstract Ag/α-Ag3VO4 stacked nanosheets were prepared through a low temperature hydrothermal route. Cetyl trimethylammonium bromide has been used as a surfactant in the preparation of Ag/α-Ag3VO4 stacked nanosheets. X-ray diffraction revealed mixed metallic silver with Ag/αAg3VO4 nanosheets which was further confirmed by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). FESEM and HRTEM images clearly showed that the silver anchored with silver vanadium oxide-stacked nanosheets. The electrochemical performance of the Ag/α-Ag3VO4-stacked nanosheets was examined by cyclic voltammetry and galvanostatic charge-discharge techniques. Both studies indicated that Ag/α-Ag3VO4 is a suitable negative electrode material for supercapacitor and delivers a maximum specific capacitance of 461 F g-1 at a specific current of 2 A g-1. The asymmetric supercapacitor device yielded a specific cell capacitance of 97 F g-1 at a specific current of 1 A g-1. The device delivers a high specific energy and specific power of 43.65 W h kg-1 and 892.8 W kg-1, respectively. --------------------------------------------------------------------------------------------------------------------Corresponding author: Kwang-Sun Ryu email : [email protected] (K.-S. Ryu) Tel: 82-52-259-2763 Fax: 82-52-259-2348

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1. Introduction Recently, supercapacitors have attracted considerable attention for energy storage applications owing to their high power uptake and delivery than batteries. This combination of attributes makes supercapacitors suitable for electric vehicles and smart grid application. On the other hand, supercapacitors suffer from low energy densities owing to the limited potential range which has been improved by the fabrication of asymmetric supercapacitor devices. The asymmetric device can combine the merits of both positrode and negatrode materials1. Most studies have been performed on positrode materials for supercapacitors, whereas only a few have examined negatrode materials for supercapacitor applications. Generally, carbon-based materials (CNT, graphene, conducting polymers and activated carbon) have been assessed as negatrodes for device fabrication2-4. This type of electrode material limits its maximum capacitance ~ 200 F g-1. Transition metal oxide-based electrode materials (RuO, SnO2, NiO, Co3O4, Fe3O4, WO3, Mn3O4, and V2O5) have a high theoretical capacitance that delivers high specific capacitance as positrodes5-12. Among these oxides, Fe3O4, WO3, Mn3O4, and V2O5 have been reported to be the negatrode materials for supercapacitor application13-16. Among these metal oxides, vanadium oxides have the unique advantages of a wide potential window in aqueous neutral electrolytes and various oxidation states (+2 to +5) which makes vanadium based oxides are suitable candidates for negatrode materials in supercapacitor applications17. The poor electronic conductivity of vanadium oxide reduces the power performance of a supercapacitor which can be improved by the addition of silver. The addition of silver can maintain the low internal resistance of the vanadium oxide electrode and increase proton (H+, Na+, K+ and Li+) diffusion throughout the electrode18. Qu et al19 reported the core-shell structure


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of polypyrrole grown on V2O5 nanoribbons as a high performance anode material for supercapacitors and they estimated the specific capacitance of 308 F g-1 at a specific current of 0.1 A g-1. Chen et al20 reported V2O5 nanowire / CNT composites for electrochemical energy storage and the electrode yielded a specific capacitance of 440 F g-1 at a specific current of 0.25 A g-1. They fabricated an asymmetric device that delivered a specific capacitance of 45 F g-1 at a discharge current density of 0.65 mA cm-2. Ye et al21 reported that 3 D reduced graphene oxidecoated V2O5 nanoribbon scaffold for a high capacity supercapacitor electrode material for supercapacitors. They used as the positrode material for supercapacitors and they estimated a specific capacitance of 437 F g-1 at a specific current of 1 A g-1. The present paper reports the preparation of silver particle-decorated, layered silver vanadium oxide nanoparticles. The structure and morphology were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The prepared silver decorated, layered silver vanadium oxide nanoparticles were used as the negatrode for a supercapacitor, and the electrochemical performance was examined. The asymmetric device was fabricated using activated carbon as the positrode and silver decorated silver vanadium oxide as the negatrode. The electrochemical performance of the asymmetric device was tested. 2. Materials and Methods All the reagents were of analytical grade and used as received. Silver acetate, ammonium metavanadate, cetyl trimethylammonium bromide (CTAB), sodium hydroxide and activated carbon were purchased from Sigma Aldrich. A 30 mM of ammonium metavanadate was dissolved in 40 ml of distilled water and 15 mM of silver acetate was dissolved in 40 ml of distilled water. A silver acetate solution was


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added to the ammonium metavanadate solution. A 50 mM CTAB solution was added to the precursor solution, which was stirred continuously for 15 minutes. 1 M NaOH was used to maintain pH of precursor solution (pH-10). The solution was transferred to the Schott Duran bottles, which was closed with a polypropylene screw cap and kept at 100 °C for 5 h. Finally the particles were collected and washed several times with ethanol and distilled water. The collected particles were dried at 200 °C for 12 h. The similar procedure was carried out to synthesis of αAg3VO4 nanoparticles without CTAB. The sample was used for further characterization. The structure and phase of the sample were measured using a Rigaku-Ultima 4 X-ray diffractometer with Cu Kα radiation. The surface morphology of the prepared samples was analyzed by FESEM (Jeol-JSM7600F) and HRTEM (Jeol- JEM-2100F). The

electrochemical

performance of the prepared samples was assessed using an IVAMSTAT instrument with either two or three electrode configurations. The working electrode was prepared by mixing the active material, activated carbon, and PTFE (polytetrafluro-ethylene) at a ratio of 85:10:5. Finally, 1 mg of active material was pasted onto pretreated nickel foam (1 cm2 and thickness ~ 0.4 mm). Ag/AgCl and platinum wire were used as the reference and counter electrode, respectively, and 1 M Na2SO4 was employed as the electrolyte for the three electrode measurements. The coin cell was assembled using the silver decorated silver vanadium oxide electrode as the negatrode (0.7 mg cm-2) and activated carbon as the positrode (1.9 mg cm-2) with a separator. Total mass of the active material is 2.6 mg. Whattman filter paper was used as the separator which had been presoaked in the electrolyte (1 M Na2SO4) for 24 h before device fabrication.


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3. Results and Discussions: 3.1 Plausible formation mechanism of Ag/ α-Ag3VO4 nanosheets

Ag Particle

Nucleation

Stacking

Stacked nanosheets

Scheme 1: Plausible mechanism for Ag/α-Ag3VO4 stacked nanosheets formation

Scheme 1 presents a plausible formation mechanism of silver nanospheres anchored with α-Ag3VO4 nanosheets. Under hydrothermal conditions, ammonium metavanadate was dissolved and hydrolyzed to form VO3- as the corner – sharing VO4 tetrahedral. The VO3- ions condensed and polymerized to form a distorted VO4 tetrahedron, further linking up by sharing the corners to form a VO42- tunnel structure. The VO42- tetrahedral tunnels can accommodate the silver ions 22. Finally, a hybrid crystal structure of Ag/ α-Ag3VO4 was formed. In the nucleation stage, αAg3VO4 particles aggregate by weak van der Waals forces to form layered nanostructures. CTAB plays an important role in preventing random aggregation of the α-Ag3VO4 layers. The layered α-Ag3VO4 nanoparticles were further stacked with each layer at the stacking process. Consequent stacking resulted in the formation of silver anchored of α-Ag3VO4 nanosheets.


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(-121) (121)

3.2 Structural and morphological studies

α-Ag3VO4

b

α - Ag3 VO4

* Metalic Ag

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(-112)

**

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(111)

(011) (200)

(-332) (-512)

(111)

(220) (301) (202) (022) (030) (400)(320) (-113) (-213) (-322) (132) (331) (223)(303)

(011) (200) 10

Intensity (a.u)

(-121) (121)

a Intensity (a.u)

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30

2θ (degree)

40

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* **

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2θ (degree)

Figure 1: (a) XRD pattern of the α-Ag3VO4 stacked nanosheets and (b) XRD pattern of the Ag/α-Ag3VO4 stacked nanosheets

The crystal structure of the prepared samples was examined by XRD. The XRD pattern of α-Ag3VO4 was presented in figure 1 (a). Figure 1(b) shows the XRD pattern of silver vanadium oxide with the metallic silver nanoparticles. The XRD patterns confirmed the mixed phase of metallic silver and monoclinic α-Ag3VO4 nanoparticles that agreed with the JCPDS card no-43-0542. The peaks at 35.8°, 37.04°, 51.6°, 62.9°, 64.5°, and 64.61° 2θ indicates the presence of metallic silver nanoparticles and agrees with the JCPDS card no-87-0598. Metallic silver can offer more effective electron transport at the electrode/ electrolyte interface which increased the rate capability of α-Ag3VO4 as the negatrode material for supercapacitor because metallic silver increase the conductivity of silver vanadium oxide.


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a

b

100 nm c

d

e

f

Ag

Ag

100 nm

100 nm

Figure 2: (a) FESEM image of the α-Ag3VO4 nanosheets, (b) HRTEM images of the α-Ag3VO4 stacked nanosheets, (c and d) FESEM images of the Ag/α-Ag3VO4 stacked nanosheets and (e and f) HRTEM images of the Ag/α-Ag3VO4 stacked nanosheets


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Figure 2 (a and b) shows the FESEM and HRTEM image of α-Ag3VO4 nanosheets. These images clearly indicate the pure α-Ag3VO4 nanosheets without Ag particle distribution. Figure 2 (c and d) presents FESEM images of silver anchored silver vanadium oxide nanosheets at various magnifications. The FESEM images confirmed the spherical silver nanoparticles with the anchored α-Ag3VO4 nanosheets. The layer of silver vanadium oxide was stacked to each other to form the nanosheets. Figure 2 (e and f) presents the HRTEM images. The Ag decorated with the layer stacked α-Ag3VO4 nanosheets can be seen clearly. The layer by layer stacking nanosheet structures maintained the structural integrity over the continuous cycling at the electrode/ electrolyte interface. Zhou et al23 reported silver particle anchored with the silver vanadium oxides and obtained Ag decorated silver vanadium oxide nanorods. Further EDAX analysis confirmed the presence of silver, vanadium, and oxygen in the prepared samples, as shown in the supporting information Figure S1 (a). The elemental composition is listed in table S1 in the supporting information. Figure S1 (b, c, d and e) presents the elemental maps of the Ag/ α-Ag3VO4 samples. 3.3 Electrochemical studies The electrochemical performance of the of Ag/ α-Ag3VO4 nanosheets was examined by CV and galvanostatic charge-discharge techniques. The proposed charge storage mechanism of vanadium oxide in an aqueous electrolyte is as follows24: V2O5 + xM+ + xe-

V 5+1-x M+x

(M+= H+, Li+, Na+, and K+).


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3.3.1 Three electrode system 3

Ni-substrate α-Ag3VO4 Ag anchored α-Ag3VO4

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e Potential (V)

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Figure 3: (a) CV curves of bare Ni-foam, α-Ag3VO4 and Ag/α-Ag3VO4 electrodes. (b and c) CV curves of the α-Ag3VO4 and Ag/α-Ag3VO4 stacked nanosheets electrode, (d) scan rate against specific capacitance, (e) charge-discharge curve of the Ag/αAg3VO4 stacked nanosheets electrode, and (f) ) specific current against specific capacitance


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The electrochemical properties of α-Ag3VO4 and Ag/ α-Ag3VO4 as the negatrodes were studied by CV within the potential range of 0 to -0.8 V (vs. Ag/AgCl). Figure 3 (a) presents the CV curves of bare Ni-foam, α-Ag3VO4 and Ag/ α-Ag3VO4 electrodes at a scan rate of 5 mV s-1. The quasi rectangular shape of the CV curves highlights the pseudocapacitance nature of the electrode. From these curves, we could observe that bare Ni-foam exhibits the negligible amount of the capacitance and Ag/ α-Ag3VO4 electrode reveals the higher area under the curve than αAg3VO4 electrode. The CV curves of α-Ag3VO4 and Ag/ α-Ag3VO4 was presented in figure 3 (b and c).

The specific capacitance was estimated using the following equation:25 ௏

ଵ

‫ = ݏܥ‬௠௩(௏ ି௏ ) ‫׬‬௏ ೎ ‫ܸ݀)ܸ(ܫ‬, ೎

ೌ

ೌ

(1)

where Cs is the specific capacitance (F g-1), m is the mass of active material (g), v is the scan rate (mV s-1), ∆V (Vc-Va) is the potential range (V), and I is the current (A). The pure α-Ag3VO4 electrode yields the capacitance of 159 F g-1 at a scan rate of 5 mV s-1. The estimated specific capacitance was 354, 339, 302, and 253 F g-1 for 5, 10, 25 and 50 mV s-1, respectively for the Ag/ α-Ag3VO4 electrode. Figure 3 d shows a plot of the scan rate as a function of the specific capacitance which indicates that the specific capacitance increases with decreasing scan rate. This phenomenon was attributed mainly to the ion exchange mechanism26. At higher scan rates, the Na+ ion intercalation / deintercalation occurs only at the surface of the electrode material, whereas at lower scan rates, the electrolyte ions (Na+) have sufficient time to intercalate / deintercalate with more active sites in the electrodes. This leads to enhanced specific capacitance at lower scan rates. The galvanostatic charge-discharge measurements were carried out within the potential range of 0 to -0.8 V. Figure S2 (a and b) presents the charge-discharge curves of bare Ni-foam,


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α-Ag3VO4 and Ag/ α-Ag3VO4 electrodes at a specific current of 2 A g-1. Figure 3 (e) shows the charge-discharge curves of Ag/ α-Ag3VO4 electrode. The Ag/ α-Ag3VO4 electrodes exhibit the linear behavior of the charge-discharge profile which indicates the pseudocapacitance nature of the electrodes. The charge - discharge curves generally consist of three parts (i) IR drop (small voltage drop) due to the internal resistance of the active material, (ii) double layer region due to the ion separation between electrode/electrolyte interfaces, and (iii) the redox component ascribed to the charge transfer reaction of silver decorated Ag3VO4 nanosheets. The specific capacitance of Ag/ α-Ag3VO4 was estimated using the following equation 26: ‫= ݏܥ‬

ூ∆௧ ௠∆௏

(2)

where Cs is the specific capacitance (F g-1), I is the specific current (A), t is the time taken for discharge (s), m is the mass of the active material (g), and ∆ V is the potential window (V). Figure 3(f) presents the various specific current versus the specific capacitance. The estimated specific capacitance for a specific current of 2, 5, 10, 20 and 30 A g-1 were 461, 378, 313, 275, and 262 F g-1, respectively. The specific capacitance decreased with increasing specific current. The reason for the capacitance loss at the higher specific current might be explained by the IR drop; activation and polarization could occur at higher specific currents, resulting in low utilization of the active material, and leading to low specific capacitance. Qu et al19 reported the core-shell structure of polypyrrole grown on V2O5 nanoribbons and estimated the specific capacitance of 308 F g-1 at a specific current of 0.1 A g-1. Chen et al. 20 produced V2O5 nanowire / CNT composites and the resulting electrode yielded a specific capacitance of 440 F g-1 at a specific current of 0.25 A g-1. In the present study, a higher specific capacitance was achieved at a higher specific current. This was attributed to Ag/ α-Ag3VO4 stacked nanosheets having a high electronic conductivity due to the metallic silver, which maintains the low internal resistance of


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the silver vanadium oxide stacked nanosheets18. The stacked nanosheets structure allows effective contact between the electrolyte (Na+ ions) and current collector which supports the sufficient ion supply for the electrode/electrolyte interface. 120

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Specific capacitance rentation (%)

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Figure 4: (a) Cyclic stability of Ag/α-Ag3VO4 stacked nanosheets electrode, (b) last few charge- discharge cycles and (c) XRD pattern of Ag/α-Ag3VO4 electrode after cycling To evaluate the cyclic stability, the electrode was subjected to continuous chargedischarge cycles. Figure 4 (a) shows the discharge capacitance of the Ag/ α-Ag3VO4 stacked nanosheets as a function of the cycle number at a specific current of 30 A g-1. After 2000 cycles, 93 % of the specific capacitance was retained. The Ag/ α-Ag3VO4 stacked nanosheets are


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believed to help maintain the structural integrity and mechanical adhesion with the current collector, which enhances the long term electrochemical stability of the electrode. Figure 4 (b) presents the last few cycles of the charge- discharge curve of Ag/ α-Ag3VO4 stacked nanosheets. After continuous 2000 cycles, Ag/α-Ag3VO4 electrode was studied through X-ray diffraction analysis which was presented in figure 4 (c). The XRD pattern confirms the βAg3VO4 crystal structure and agreed with JCPDS card no-43 0543 along with the metallic silver. This result indicates the crystal structure was changed (α-phase to β-phase) due to continuous ion intercalation/deintercalation. 3.3.2 Two electrode system (Asymmetric device) Three electrode systems are used to measure the electrochemical behavior of Ag/ αAg3VO4, as the working electrodes (negative). This analysis suggests that the Ag/ α-Ag3VO4 stacked nanosheets electrode is a suitable candidate for asymmetric device fabrication. Activated carbon was used as the positrode for asymmetric device fabrication. Figure S3 shows the charge-discharge curve of the activated carbon electrode. We have estimated the specific capacitance of 126 F g-1 at a specific current of 2 A g-1. The capacitance of positrode and negatrode is associated with the mass of the active material. In order to balance the charges, mass of the positrode and negatrode should be balanced. Mass balance was carried out using following equation27-28, ௠శ ௠ష

஼ ௑௏

= ஼ ష ௑ ௏ష శ

శ

(3)

where m+ is mass of the positrode (activated carbon) (g), m- is the mass of the negatrode (Ag/ α-Ag3VO4 stacked nanosheets) (g), C- is the specific capacitance of the negatrode (F g-1), V- is the potential range of the negatrode (V), C+ is the specific capacitance of positrode (F g-1), and V+ is the potential range of the positrode (V). The estimated optimal mass ratio was 3.688. The


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total mass of the active material was 2.6 mg. These electrodes were used to fabricate the coin cell type asymmetric device, which was tested. The results are presented in this section. -1

25 mV s -1 50 mV s -1 100 mV s

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Figure 5: (a) CV curves of the asymmetric device, (b) Scan rate as a function of the specific capacitance and (c) charge-discharge curve of the asymmetric device, and (d) ) specific current as a function of the specific capacitance

Figure 5(a) shows the CV curves of the asymmetric device. The shape of the CV curves illustrates the pseudocapacitance nature of the device. Figure 5 (b) shows the specific cell capacitance as a function of the scan rate. The specific cell capacitance was calculated from equation (1). The estimated specific cell capacitance was 66, 44, and 25 F g-1 at a scan rate of 25, 50, and 100 mV s-1. Figure 5 (c and d) resents the charge and discharge curves and the specific


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cell capacitance as a function of the specific current of the asymmetric device. The specific cell capacitance was estimated from equation 2. The asymmetric device yields the maximum specific cell capacitance 97, 84, 61, 28, and 17 F g-1 at a specific current of 1, 2, 4, 8, and 10 A g-1, respectively. The cyclic stability of the asymmetric supercapacitor device was measured for 2000 continuous cycles at 10 A g-1. After 2000 cycles, 13 % degradation of the specific cell capacitance was observed. Figure 6 (a and b) shows the cyclic stability at every 200 cycles and few cycles of the charge discharge curve. 120

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Figure 6: (a) Cyclic stability of the asymmetric device and (b) first few charge- discharge cycles Fig 7(a) presents the Nyquist plot of the Ag/ α-Ag3VO4 stacked nanosheets. In the high frequency region, a semicircle was observed due to the polarization effect In the lower frequency region, a straight line was observed, which is lower than the 90º angle to the real axis due to the mass transfer effect or superposition effect29. This superposition effect is called the Warburg impedance.. The electrochemical impedance of the Ag/ α-Ag3VO4 stacked nanosheets was measured in the frequency range of 0.01 Hz - 100 kHz, at the open circuit potential. The spectrum was fitted with an equivalent circuit. From this plot, a charge transfer resistance (Rct) of 16 Ω was obtained.


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Asymmetric Device

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Specifc enegry (W h kg )

Z' (Ω)

Figure7: (a) Nyquist plot of the asymmetric device (inset – fitting circuit and high frequency region) and (b) Ragone plot of the asymmetric device.

Another important key factor of a supercapacitor device is the specific energy and specific power, which is shown (Ragone plot) in Figure 7 (b). The specific energy and specific power was estimated using the following equations 29: ଵ

‫ = ܧ‬ଶ ‫ ܸܥ‬ଶ

(4)

ா ௧

(5)

ܲ=

where E is the specific energy (W h kg-1), C is the specific cell capacitance (F g-1), V is the potential range (V), P is the specific power (W kg-1), and t is the discharge time (t). The estimated specific energy values are 43.65, 37.80 27.45, 12.60, and 7.65 W h kg-1 and the specific power values were 892.8, 1809.5, 3600.0, and 7316.0 W kg-1, respectively. Chen et al 20 produced V2O5 nanowire / CNT composites for asymmetric supercapacitor devices and reported a specific energy of 16 W h kg-1 at a specific power of 75 W kg-1. Qu et al30 have reported V2O5.0.6H2O nanoribbons for asymmetric supercapacitors and estimated the specific energy of


16

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20.3 W h kg-1 at a specific power of 2 kW kg-1. Reduced graphene oxide supported V2O5 networks for asymmetric supercapacitor was reported by Saravankumar et al31. They have reported the specific energy of 7.4 W h kg-1. Here, the Ag/ α-Ag3VO4 based supercapacitor devices delivered a higher specific energy compared then literature. This enhancement may be the advantages of the metallic silver anchored with silver vanadium oxide stacked nanosheets. All the electrochemical studies suggest that the Ag/ α-Ag3VO4 stacked nanosheets is a suitable negatrode material for supercapacitor device fabrication.

4. Conclusion: Ag/ α-Ag3VO4 stacked nanosheets are synthesized using a hydrothermal method. XRD revealed the mixed phase of metallic silver and a monoclinic α-Ag3VO4 crystal structure. FESEM and HRTEM revealed the silver anchored stacked nanosheets structure. The three electrochemical studies confirmed that the Ag/ α-Ag3VO4 stacked nanosheets are a better negatrode material for supercapacitor device fabrication. The asymmetric device yielded a higher specific capacitance of 97 F g-1 at a constant specific current of 1 A g-1. The devices delivered a high specific energy of 43.65 W h Kg-1 at a specific power of 892.80 W kg-1. These results are comparable to Pb-acid and Ni-MH batteries. ASSOCIATED CONTENT Supporting Information Elemental composition of Ag/ α-Ag3VO4 stacked nanosheets table S1. Figure S1 (a, b, c, d and e) EDAX pattern of Ag/ α-Ag3VO4 stacked nanosheets and elemental mapping. Figure S2 ( a and b)- Charge discharge curve of α-Ag3VO4 electrode and figure S3- charge discharge curve of activated carbon.


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Acknowledgement This work was supported by the Priority Research Centers Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (MEST) of the Korean government (2009-0093818). REFERENCES 1. J. Xu, Q. Wang, X. Wang, Q. Xiang, B. Liang, D. Chen, and G. Shen. Flexible Asymmetric supercapacitors based upon Co9S8 nanorod//Co3O4@RuO2 nanosheets arrays on carbon cloth, ACS Nano.2013, 7, 5453-5462. 2. Y. Wang, Z. Shi, Y. Huang, Y. Ma, C. Wang, M. Chen, and Y. Chen. Supercapacitor devices based on graphene materials, J. Phys. Chem. C, 2009, 113, 13103–13107. 3. L. Wang, X. Feng, L. Ren, Q. Piao, J. Zhong, Y. Wang, H. Li, Y. Chen, and B. Wang. Flexible solid-state supercapacitor based on a metal-organic framework interwoven by electrochemically-deposited PANI. J. AM. Chem. Soc. 2015, 137, 4920-4923. 4. X. Du, C. Wang, M. Chen, Y. Jiao, and J. Wang.

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Synopsis TOC

Power density (W kg-1)

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Enegrydensity(Whkg)


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Synthesis of Ag Anchored Ag3VO4 Stacked Nanosheets: Toward a

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