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19 Simagis Live Smart Web Pathology: Smart Imaging Technologies Co, http://host.simagis.com.

20 Mirzaee M.

Pour G.B. Design and fabrication of ultracapacitor based on paper substrate and BaTiO3/PEDOT: PSS separator film.

C m = [ m S ( V 2 − V 1 ) ] − 1 ∫ V 1 V 2 I d V (1)

21 Ping Y.

Gong Y.

Fua Q.

Pan C. Preparation of three-dimensional graphene foam for high performance Supercapacitors.

22 Obeidat A.M.

Gharaibeh M.A.

Obaidat M. Solid-state supercapacitors with ionic liquid gel polymer electrolyte and polypyrrole electrodes for electrical energy storage.

23 Cao L.

Tang G.

Mei J.

Liu H. Construct hierarchical electrode with Ni x Co 3-x S 4 nanosheet coated on NiCo2O4 nanowire arrays grown on carbon fiber paper for high-performance asymmetric supercapacitors.

C m = I [ m ( d V d t ) ] − 1 (2)

24 Dai S.

Xu W.

Xi Y.

Wang M.

Gu X.

Guo D.

Hu C. Charge storage in KCu 7 S 4 as redox active material for a flexible all-solid-state supercapacitor.

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25 Alvi F.

Ram M.K.

Basnayak P.A.

Stefanakos E.

Goswamid Y.

Kumar A. Graphene–polyethylenedioxythiophene conducting polymer nanocomposite based supercapacitor.

19 Simagis Live Smart Web Pathology: Smart Imaging Technologies Co, http://host.simagis.com.

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Bae J. Low-cost, high-efficiency conductive papers fabricated using multi-walled carbon nanotubes, carbon blacks and polyvinyl alcohol as conducting agents.

27 Karthika P.

Rajalakshmi N.

Dhathathreyan K.S. Flexible polyester cellulose paper supercapacitor with a gel electrolyte.

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Lang J.

Xu S.

Wang X. Oxygen-enriched activated carbons from pomelo peel in high energy density supercapacitor.

E ( W h K g ) = 1 2 1000 3600 C S V 2 (3)

P ( W K g ) = E × 3600 t (4)

Fig. 1 (a) schematic of the symmetric paper supercapacitor with the structure of GNPs electrodes (b) image of the fabricated supercapacitor (c) image of paper supercapacitor in bend state.

Fig. 2 SEM images of paper surface (a) before and (b) after BaTiO 3 gel separator coating (c) PVA gel electrolyte surface (d) GNPs electrode surface (e) TEM image of GNPs.

Fig. 3 (a) Cyclic voltammetry (C-V) at 20 mV/s and 150 mV/s (b) Galvanostatic charge-discharge results from paper supercapacitor with the graphite nanoparticles electrodes.

Fig. 4 (a) Schematic of the paper supercapacitor with the graphene electrodes (b) TEM image of the graphene.

Fig. 5 (a) Cyclic voltammetry (C-V) at 20 mV/s and 150 mV/s (b) Galvanostatic charge-discharge results from paper supercapacitor with the graphene electrodes.

Fig. 6 (a) Schematic of the paper supercapacitor with the CNTs electrodes (b) TEM image of the CNTs (c) SEM image of CNTs film surface.

Fig. 7 (a) Cyclic voltammetry (C-V) at 20 mV/s and 150 mV/s (b) Galvanostatic charge-discharge results from paper supercapacitor with CNTs electrodes.

The schematic of the symmetric paper supercapacitor (dimension 3 cm × 6 cm) with the structure of GNPs electrodes and also the image of the fabricated supercapacitor were illustrated in Fig. 1 . As can be seen in Fig. 1 , using the push coating, a thin layer of gel separator, electrolyte and electrode has been coated on both sides of the paper. The SEM images of the paper surface before and after the coating of BaTiOand also the PVA gel electrolyte surface and GNPs electrode surface morphology have been shown in Fig. 2 . The SEM image of the BaTiOsurface shows the pores of the surface were filled with gel separator. In the Fig. 2 (e), the TEM image of the GNPs has been shown. The average size of GNPs diameter analyzed by using Simagis Live [] was 40 nm. The specific capacitance of the symmetric paper supercapacitor was measured using cyclic voltammetry and charge-discharge methods. The cyclic voltammetry technique has been done in voltage scan rates 20 mV sand 150 mV s. The C-V curves of the paper supercapacitor in the potential range −1 V to +1 V were presented in Fig. 3 (a). As it can be seen in Fig. 3 (a), for scan rate 150 mV sthe current was increased from -1.1 A to 2.17 A and for the scan rate 20 mV sthe current was changed from -0.3 A to 0.62 A. The specific capacitance of the supercapacitors using cyclic voltammetry method can be obtained from the following formula []:Where S is the voltage scan rate and m is the mass of the electrode materials. From Eq. (1) the specific capacitances of the symmetric paper supercapacitor with GNPs electrode for 150 mV sand 20 mV swere 79 F gand 380 F grespectively. Ping et al. [] showed the specific capacitance of graphene supercapacitor is larger at low-speed voltage scan that due to slow charge/discharge. The charge-discharge curves for symmetric paper supercapacitor with current density 0.06 mA cmwere shown in Fig. 3 (b). As it can be seen in Fig. 3 (b) the behavior of the paper supercapacitor as like a conventional capacitor. The specific capacitance of the supercapacitor using galvanostatic method can be obtained the following formula []:Where dv/dt is the absolute value of the slope of the discharging curve. Using the Eq. (2) the specific capacitance of the paper supercapacitor was 163 F gthat is inside the range of the capacitance of C-V curves. The schematic of the symmetric paper supercapacitor based on the graphene electrodes is shown in Fig. 4 (a). In this structure using push coting method on the gel electrolyte film, a layer of the graphene has been coated. The TEM image of the graphene has been shown in Fig. 4 (b). The C-V curves of the symmetric paper supercapacitor based on the graphene electrode were illustrated in Fig. 5 (a). From Eq. (1) the specific capacitances of the symmetric paper supercapacitor with graphene electrode for 150 mV sand 20 mV swere 87 F gand 410 F grespectively. The charge-discharge curves for paper supercapacitor based on graphene electrodes were presented in Fig. 5 (b). From Eq. (2) the specific capacitance of the paper supercapacitor was 310 F gthat is inside the range of the capacitance of C-V curves. Dai et al. [], showed the specific capacitance for the paper supercapacitor based on the KCu/graphene electrode and PVA electrolyte was 483 F g. The supercapacitor based on the graphene-PEDOT electrode has been investigated in Ref. []. That paper described the specific capacitance of the supercapacitor was estimated to be 374 F g. The schematic of the symmetric paper supercapacitor based on the CNTs electrodes was displayed in Fig. 6 (a). Fig. 6 (b) shows the TEM image of the CNTs. The CNTs diameter were analyzed using Simagis Live [] and were around 7–55 nm. The average size of CNTs diameter was 15 nm. Using spry method, a thin layer of CNTs has been coated on the gel electrolyte film. The SEM images of CNTs electrode surface have been shown in Fig. 6 (c). The C-V curves of the symmetric paper supercapacitor based on CNTs electrodes were presented in Fig. 7 (a). The C-V curve of the symmetric paper supercapacitor at 150 mV sshowed a nearly rectangular shape. From Eq. (1) the specific capacitances of the symmetric paper supercapacitor with CNTs electrode for 150 mV sand 20 mV swere 164 F gand 411 F grespectively. The charge-discharge curves for the symmetric paper supercapacitor based on CNTs electrodes were illustrated in Fig. 7 (b). From Eq. (2) the specific capacitance of the paper supercapacitor was 520 F g. Comparison of the specific capacitance of the symmetric paper supercapacitors based on graphite nanoparticles, graphene and CNTs electrodes shows that the capacitance of the CNTs supercapacitor is higher than the graphene and graphite nanoparticles supercapacitor. Kalam et al. [], reported the paper supercapacitor based on CNTs electrode and the PVA gel at the voltage scan rate of 150 mV/s. They showed the specific capacitance of the paper supercapacitor was 219 F g. In another study, the polyester paper supercapacitor has been investigated based on the CNTs electrode and PVA gel electrolyte by Karthika et al. []. They reported the specific capacitance of the paper supercapacitor was 276 F gat 5 mV/s. The energy density and the power density can be obtained from []: