{Graphene based sulfonated polyvinyl alcohol hydrogel nanocomposite for flexible supercapacitors}
http://dx.doi.org/10.5599/jese.1031 197
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207; http://dx.doi.org/10.5599/jese.1031
Open Access : : ISSN 1847-9286
www.jESE-online.org
Original scientific paper
Graphene based sulfonated polyvinyl alcohol hydrogel
nanocomposite for flexible supercapacitors
Subhakaran Singh Rajaputra1,2, Nagalakshmi Pennada1,2, Anjaneyulu Yerramilli1,2,
Naga Mahesh Kummara1,
1Centre for Advanced Energy Studies, Koneru Lakshmaiah Education Foundation, Vaddeswaram,
Guntur Dist. 522 502, AP, India
2Department of Chemistry, Koneru Lakshmaiah Education Foundation, Vaddeswaram, Guntur Dist.
522 502, AP, India
*Corresponding author: nagamaheshk@gmail.com
Received: June 22, 2021; Revised: July 22, 2021; Accepted: July 29, 2021; Published: August 3, 2021
Abstract
Graphene based sulfonated polyvinyl alcohol (PVA) hydrogel was synthesized and its
performance as nanocomposite gel polymer electrolyte was investigated for application
in quasi solid-state flexible supercapacitors. Hydrothermally reduced graphene (HRG) was
synthesized through hydrothermal reduction of graphene oxide (GO). Sulfonated PVA
hydrogel (SPVA) was synthesized with predetermined quantities of HRG to obtain
nanocomposite gel polymer electrolytes coded as SPVA-HRG-x (x = content (wt.%) of HRG).
The amorphous nature of SPVA-HRG-x was determined using X-ray diffraction (XRD)
technique. The electrochemical performance of SPVA-HRG-x was evaluated using
techniques like cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and
electrochemical spectroscopy (EIS) studies of a lab scale supercapacitor cell, fabricated
using hydrothermally reduced carbon cloth (CCHy) current collectors coated with HRG
(HRG-CCHy). In SPVA-HRG-0.5 electrolyte, HRG-CCHy exhibited specific capacitance of
200 F g-1 at 1 A g-1 and specific energy of 6.1 Wh kg-1 at specific power of 1 kW kg-1 and
retained 93 % of its initial capacitance even after 5000 GCD cycles. The incorporation of
SPVA with 0.5 wt.% of HRG-CCHy can be attributed to the increase in amorphous nature
of SPVA-HRG-0.5, which in-turn lowers its impedance. This contributed to the remarkable
supercapacitive behaviour of HRG-CCHy, demonstrating its potential as gel polymer
electrolyte (GPE) for application in quasi solid-state flexible supercapacitors.
Keywords
Electrochemical double-layer capacitors; gel polymer electrolyte; carbon cloth; cyclic
voltammetry; electrochemical impedance; specific capacitance; specific energy.
http://dx.doi.org/10.5599/jese.1031
http://dx.doi.org/10.5599/jese.1031
http://www.jese-online.org/
mailto:nagamaheshk@gmail.com
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207 POLYVINYL ALCOHOL HYDROGEL NANOCOMPOSITE
198
Introduction
In recent years, there has been sharp increase in the development of flexible supercapacitors
(FSCs) for electronic devices as power sources, which have to be ultra-thin and flexible in-order to
serve their purpose [1-4]. FSCs with high specific energy, specific power and excellent cycle life are
much desirable to supply the rising market of flexible and wearable electronic devices in the near
future [5,6].
To increase the performance of supercapacitors, the usage of various types of carbons,
mixed/binary metal oxide and sulfide-based electrode materials like nanochains [7], nanoflowers
[8] and other nanostructures [9-11] has been widely reported. Carbon based materials are most
widely used electrode materials in supercapacitor application, due to their high surface area and
capability of storing charge in the form of an electric-double layer [12,13]. Currently, reduced
graphene oxide (RGO), a graphene-based material with high ionic conductivity and surface area, has
emerged as a potential electrode material in FSCs and alternative to activated carbon [14]. The main
components of a FSC are flexible electrodes, solid or quasi-solid-state electrolyte and a porous
separator to prevent short-circuit [15]. The synergy between the electrolyte and the electrode
material creates a significant impact on the properties of a supercapacitor, like charge-discharge
capabilities, cyclic stability, energy storage in the form of charge, and power delivery [16].
The rate performance and specific power of a supercapacitor can be increased by increasing ionic
conductivity of the electrolyte [17]. Most of FSC assemblies use gel polymer electrolytes (GPEs) to
prevent leakage and packaging issues, as in the case of liquid electrolytes [18,19]. GPEs contain a
discontinuous phase of solvent entrapped inside a continuous phase of three-dimensional polymer
network [20]. Hydrogels of polyvinyl alcohol (PVA) contain hydroxyl groups which contribute to its
hydrophilic nature by absorbing large amounts of water, in-turn enhancing the conductivity of
electrolyte ions [26] and establishing stable contact at the interface of electrode and electrolyte [21].
Sulfonation of PVA hydrogels using proton donor like sulfuric acid (H2SO4) enhances their ionic
conductivity [22,23]. In the past, extensive usage of PVA-H2SO4 (SPVA) as GPE in supercapacitors has
been reported alongside electrode materials like activated carbon [24], carbon nanotubes (CNTs)
[25] and graphene [26-29]. Incorporation of nanofillers and redox-active materials into GPEs leads
to rise in amorphous nature thereby improving ion conductivity [30, 31]. Recently, redox-additives
like Na2MoO4 [5], hydroquinone [32], alizarin red [33] and indigo carmine [34] have been
incorporated into PVA-H2SO4 for application in supercapacitors.
Inorganic fillers like nano SiO2 [35], nano TiO2 [36], Sb2O3 [37] and graphene oxide (GO) [38] have
been incorporated for improving performance in PVA based GPEs. Several reports have mentioned
the usage of GO as a nanofiller in GPEs in various electrochemical devices [39-41]. Yang et al. [42]
reported that incorporation of GO into polyvinylidene difluoride (PVDF) based GPE enhances its ionic
conductivity by forming 3D network structures in the polymer matrix facilitating the transport of ions.
The current paper deals with incorporation of hydrothermally reduced graphene oxide (HRG) into
SPVA hydrogels, performed for the first time to obtain nanocomposite GPEs and evaluate their
electrochemical performance for application in quasi solid state flexible supercapacitors. GO was
synthesized using a modified Hummer’s method and reduced hydrothermally to obtain HRG. Carbon
cloth (CC) was modified using a hydrothermal method to obtain hydrothermally reduced carbon
cloth (CCHy) and use it as a flexible current collector. Nanocomposite GPEs were prepared by
sulfonating PVA hydrogel using H2SO4, followed by addition of calculated amounts of HRG ranging
from 0.1 to 1.0 wt.% to obtain HRG incorporated SPVA GPEs, hereafter referred as SPVA-HRG-x
(x = content (wt.%) of HRG). Electrochemical performance of developed SPVA-HRG-x was evaluated
S. S. Rajaputra et al. J. Electrochem. Sci. Eng. 11(3) (2021) 197-207
http://dx.doi.org/10.5599/jese.1031 199
using an in-house fabricated supercapacitor single cell with electrodes of HRG coated CCHy
(HRG-CCHy).
Experimental
Materials
Graphite powder (particle size <20 µm) and sodium nitrate (NaNO3) were obtained from Sigma-
Aldrich Inc. and Merck Specialities Pvt. Ltd., India, respectively. Carbon cloth was obtained from
Avcarb, USA. Ethanol 99.9 % was procured from Changshu Hongsheng Fine Chemicals Co. Ltd.,
China. Poly (vinyl alcohol) (PVA) (M.W. ̴125,000), polyvinylidene difluoride (PVDF) (homopolymer
powder, M.W. ̴320,000), N-methyl-2-pyrrolidone (NMP), sodium hydroxide (NaOH) pellets,
sulphuric acid (H2SO4) 98 %, hydrogen peroxide (H2O2) (30 % w/v), hydrochloric acid (HCl) 35–38 %,
and propan-2-ol (Isopropanol/IPA) were purchased from S D Fine-Chem Ltd., India. Potassium
permanganate (KMnO4) was obtained from Loba Chemie Pvt. Ltd., India. Whatman qualitative filter
paper: grade 1 (circles, diameter 125 mm) purchased locally was used as a separator in two
electrode studies. An in-house fabricated lab scale two electrode cell assembly made up of acrylic
plates was used to carry out full-cell studies. Always deionized (DI) water was used in preparing
various solutions.
Method
Synthesis of HRG
HRG was synthesized following the procedure reported in our previous work [43]. Firstly, a
modified Hummer’s method was followed for synthesizing GO. In 50 mL of conc. H2SO4, 1 g of NaNO3
was added and stirred for few minutes, followed by dispersing 1 g of graphite powder into it. The
above dispersion was stirred at <5 oC in an ice bath for 4 h continuously, followed by slow addition
of 6 g of KMnO4. The above mixture was stirred uninterruptedly for 48 h at room temperature (RT).
92 mL of DI water was slowly added to the above mixture and stirred for two more hours. Later,
10 mL of 30 % H2O2 was added to the mixture leading to change in dispersion color from brown to
yellow, indicating the formation of GO. The collected GO precipitate was washed with 1 M HCl and
DI water and centrifuged. The resultant precipitate was finally washed using ethanol and vacuum
dried at 70 oC for 12 h. Later, the sample was finely crushed to obtain GO powder. 200 mg of GO
powder was dispersed in 200 mL through ultrasonication. The pH of the dispersion was maintained
at 11 using NaOH pellets. The dispersion was then transferred into a Teflon lined hydrothermal
reactor (300 mL) and autoclaved for 14 h at 180 oC. The precipitate collected after the reaction was
washed several times using DI water and dried under vacuum for 12 h at 60 oC. The dried sample
was crushed to obtain a fine powder of HRG.
Preparation of CCHy
CCHy was prepared following the procedure reported in our previous work [44]. Commercially
obtained carbon cloth (CC) (50 cm2) was oxidized via chemical route. An acidic mixture of 20 mL of
H2SO4 and 10 mL of HNO3 was prepared into which a pristine CC was dropped and stirred at RT,
followed by slow addition of 3 g of KMnO4 and 100 mL of DI water, and stirred for 3 h. Later, 5-10 mL
of 30 % H2O2 was added to the above mixture resulting in a clear solution with oxidized carbon cloth
in it. The oxidized CC was washed with DI water and transferred into a Teflon lined hydrothermal
reactor (300 mL), filled with DI water and autoclaved for 14 h at 180 °C. Later, the reduced CC was
http://dx.doi.org/10.5599/jese.1031
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207 POLYVINYL ALCOHOL HYDROGEL NANOCOMPOSITE
200
vacuum dried at 70 °C for 6 h. The hydrothermally reduced CC (CCHy) thus obtained was used as a
current collector in the following two electrode cell studies.
Preparation of SPVA
To prepare SPVA, 270 μL of H2SO4 was added to 4 mL of DI water. Then, 0.5 g of PVA was added
to this mixture, and stirred at 80 °C till all PVA gets dissolved, resulting in a transparent viscous liquid.
Preparation of SPVA-HRG-x
HRG based SPVA nanocomposite was prepared by adding predetermined quantities of HRG
ranging from 0.1 to 1.0 wt. % to SPVA, separately. The HRG was dispersed in IPA using
ultrasonication and added to the cooled SPVA and stirred continuously at 80 °C for 30 min, resulting
in dark coloured SPVA-HRG-x. The obtained SPVA-HRG-x were coded as SPVA-HRG-0.1, SPVA-HRG-
0.2, SPVA-HRG-0.5 and SPVA-HRG-1.0 for SPVA incorporated with 0.1, 0.2, 0.5 and 1.0 wt. % of HRG,
respectively. Figure 1 shows the optical images of prepared SPVA and SPVA-HRG-x.
Figure 1. Optical images of (a) SPVA; (b) SPVA-HRG-0.1; (c) SPVA-HRG-0.2; (d) SPVA-HRG-0.5;
(e) SPVA-HRG-1.0
Characterization studies
X-ray diffraction (XRD) technique (Rigaku Miniflex 600) was used to analyse all GPEs.
Electrochemical workstation (PARSTAT PMC 2000A) was used to evaluate the electrochemical
performance of prepared SPVA-HRG-x. HRG-CCHy was prepared by coating HRG (1 mg cm-2) over
CCHy. Ink of HRG was prepared by dispersing 1.8 mg of HRG in 100 μL of NMP along with 2 μL of
10 wt. % PVDF/NMP solution by ultrasonication. HRG ink was then deposited over flexible CCHy
current collectors, followed by drying under vacuum for 15 min at 120 oC. Strands of HRG coated
CCHy (HRG-CCHy) were placed on both sides of a GPE coated Whatman filter paper and packed in
between acrylic plates tightly to fabricate a cell. Approximately, 100 μL of GPE was utilized during
fabrication each cell. The prepared cell was then tested in two electrode configuration using cyclic
voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance
spectroscopy (EIS) techniques to evaluate the performance of SPVA-HRG-x.
The specific capacitance (Cs), specific energy (Ed) and specific power (Pd) of HRG-CCHy in all GPEs
were calculated from GCD data, using the equations (1) to (3) [45].
s 2
I t
C
m V
=
(1)
S. S. Rajaputra et al. J. Electrochem. Sci. Eng. 11(3) (2021) 197-207
http://dx.doi.org/10.5599/jese.1031 201
2
S
d
8
C V
E
= (2)
d
d
E
P
t
=
(3)
where I represent constant discharge current, Δt represents discharge time, ΔV represents discharge
potential window and m represents the mass of the active material on one electrode.
Results and discussion
XRD analysis
Figure 2 shows X-ray diffraction patterns of pure PVA, SPVA and SPVA-HRG-x. The diffraction
pattern of pure PVA shows a characteristic semi-crystalline peak at 2 value of around 19.6 [46]. In
the case of SPVA, H2SO4 addition disturbs the semi-crystalline nature of pure PVA, thereby increasing
its amorphous nature [47]. From diffraction patterns of all SPVA-HRG-x it can be inferred that by
increase in HRG concentration the intensity of peak around 2 value of 19.6 decreased, indicating
an increase in amorphous nature of GPEs [48]. The addition of HRG may contribute to the increase
in amorphous nature of the SPVA-HRG-x [42], thereby enhancing the rate of penetration and
conduction of ions [49].
Figure 2. X-ray diffraction patterns of pure PVA, SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2,
SPVA-HRG-0.5 and SPVA-HRG-1.0
Electrochemical studies
CV studies
The electrochemical performance of HRG-CCHy was evaluated by executing CV studies for all five
GPEs at various scan rates, ranging from 10 to 100 mV s-1 , within potential window 0 to 1 V. The
area under near rectangular CV curve is proportional to the double-layer capacitance of the
electrode material [50]. Figure 3a compares CV curves of HRG-CCHy in all GPEs at the scan rate of
50 mV s-1, with HRG-CCHy showing comparatively superior double-layer capacitance in SPVA-HRG-
0.5 electrolyte. From CV curves of HRG-CCHy in all GPEs depicted in Figure 3a, an increase of the
area under near rectangular CV curve is observed by increasing HRG content in SPVA-HRG-x
electrolyte up to 0.5 wt.%. The decrease in CV curve area of HRG-CCHy in SPVA-HRG-1.0 compared
http://dx.doi.org/10.5599/jese.1031
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207 POLYVINYL ALCOHOL HYDROGEL NANOCOMPOSITE
202
to SPVA-HRG-0.5, indicates a decline in double-layer capacitance of HRG-CCHy in SPVA-HRG-1.0 due
to the excess concentration of HRG in SPVA-HRG-1.0, which could resist the flow of ions due to
formation of agglomerates by restacking of HRG layers [45,48]. The CV curves of HRG-CCHy in SPVA-
HRG-0.5 electrolyte at multiple scan rates ranging from 10 to 100 mV s-1 (Figure 3b), indicate better
rate capability and reversibility [51].
Figure 3. (a) Comparative CV curves of HRG-CCHy in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2,
SPVA-HRG-0.5 and SPVA-HRG-1.0 at scan rate of 50 mV s-1; (b) CV curves of HRG-CCHy in
SPVA-HRG-0.5 at scan rates ranging from 10 to 100 mV s-1
GCD studies
The charge-discharge behaviour of HRG-CCHy in all five GPEs was evaluated by performing GCD
studies at various constant current densities ranging from 0.5 to 10 A g-1, within the potential window
0 to 1 V. Figure 4a compares GCD curves of HRG-CCHy in all GPEs at 1 A g-1. It is obvious that HRG-
CCHy shows better charging and discharging ability in SPVA-HRG-0.5 electrolyte, compared to the rest
of the GPEs, with an impressive specific capacitance of 200 F g-1 at 1 A g-1 with lowest IR drop of around
0.07 V. Figure 4b shows GCD curves of HRG-CCHy in SPVA-HRG-0.5 electrolyte at multiple constant
current densities ranging from 0.5 to 10 A g-1. Figure 4c represents the IR drop plot of HRG-CCHy in all
GPEs at various constant current densities ranging from 0.5 to 10 A g-1, indicating the lower equivalent
series resistance (ESR) and superior conductivity of HRG-CCHy when SPVA-HRG-0.5 was used as
electrolyte [52]. Figure 4d represents the Ragone plot of HRG-CCHy in all GPEs, indicating superior
specific energy to power ratio of HRG-CCHy in SPVA-HRG-0.5, like 6.1 Wh kg-1 of specific energy at
specific power of 1 kW kg-1. In SPVA-HRG-1.0 electrolyte, HRG-CCHy showed a sharp increase in IR
drop and decrease in specific energy at current densities ≥7 A g-1, indicating an abrupt increase of ESR
of the cell. This distinct behavior of SPVA-HRG-1.0 electrolyte at higher current densities, could result
from the excess of HRG in SPVA-HRG-1.0, which could lead to restacking of HRG layers forming
agglomerates, in-turn resisting the flow of ions [39,42].
Cyclic stability
Figure 5a represents the cyclic stability of HRG-CCHy in all GPEs for 5000 GCD cycles at 2 A g-1.
Even after 5000 GCD cycles, HRG-CCHy retained 82, 86, 89, 93 and 87 % of their initial specific
capacitances in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2, SPVA-HRG-0.5 and SPVA-HRG-1.0, respect-
tively. Figure 5b shows GCD curves of HRG-CCHy in SPVA-HRG-0.5 before and after cycling for 5000
cycles, which clearly establishes the notable charge-discharge stability of HRG-CCHy in
S. S. Rajaputra et al. J. Electrochem. Sci. Eng. 11(3) (2021) 197-207
http://dx.doi.org/10.5599/jese.1031 203
SPVA-HRG-0.5. Table 1 represents the comparison of supercapacitive performances of some carbon-
based electrode materials in sulfonated PVA based GPEs.
Figure 4. (a) GCD curves of HRG-CCHy in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2, SPVA-HRG-0.5 and SPVA-
HRG-1.0 at 1 A g-1; (b) GCD curves of HRG-CCHy in SPVA-HRG-0.5 at 0.5, 1, 2, 4, 5, 7 and 10 A g-1; (c) IR drop
plot; (d) Ragone plot of HRG-CCHy in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2, SPVA-HRG-0.5 and SPVA-HRG-1.0
Figure 5. (a) Cyclic stability of HRG-CCHy in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2, SPVA-HRG-0.5 and
SPVA-HRG-1.0 at 2 A g-1 for 5000 GCD cycles; (b) GCD curves of HRG-CCHy in SPVA-HRG-0.5 before and
after cycling for 5000 GCD cycles at 2 A g-1
http://dx.doi.org/10.5599/jese.1031
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207 POLYVINYL ALCOHOL HYDROGEL NANOCOMPOSITE
204
Table 1. Comparison of supercapacitive performances of carbon-based electrode materials in sulfonated
PVA based GPEs
Electrolyte Electrode material Specific capacitance Reference
PVA/H2SO4 Graphene 190 F g-1 at 0.5 A g-1 [28]
PVA/H2SO4 RGO-PVA composite film 184.6 F g-1 at 1 A g-1 [53]
PVA/H2SO4 N-doped porous carbon 232 F g-1 at 0.5 A g-1 [54]
PVA/H2SO4/H3BO3 Poly carbon nanofibers 134 F g-1 at 1 A g-1 [23]
PVA/H2SO4/Na2MoO4 MoS2-NCNT 95.14 F g-1 at 1 mA [55]
PVA/H2SO4/HRG-0.5 HRG 200 F g-1 at 1 A g-1 Present work
EIS studies
The EIS studies were performed at ac amplitude of 5 mV and within the frequency range of
100 kHz to 0.1 Hz. Figure 6a represents Nyquist plots of HRG-CCHy in all five GPEs. For all
SPVA-HRG-x, the imaginary impedance part in the low frequency region was near perpendicular to
the real axis, indicating near ideal capacitive behaviour of the cell. From Nyquist plots, it is evident
that HRG-CCHy has low impedance in SPVA-HRG-0.5 compared to other GPEs [56]. The inset image
of Figure 6a exhibits the magnified image of Nyquist plots, where SPVA-HRG-0.5 electrolyte showed
lower electrolyte resistance compared to other GPEs [57]. Figure 6b represents the Nyquist plot of
HRG-CCHy in SPVA-HRG-0.5 before and after 5000 GCD cycles. The size of the semicircle in the high
frequency region of the Nyquist plot indicates charge transfer resistance [58,59]. The inset image of
Figure 6b exhibits the magnified image of Nyquist plots, where it can be inferred that diameter of
the semi-circle of SPVA-HRG-0.5 increased after cycling 5000 GCD cycles. This confirms the increase
of charge transfer resistance after cycling [57,58]. Near-vertical line observed in the low frequency
region of Nyquist plot for SPVA-HRG-0.5 indicates superior capacitive behaviour compared to other
GPEs [60].
Figure 6. (a) Nyquist plots of HRG-CCHy in SPVA, SPVA-HRG-0.1, SPVA-HRG-0.2, SPVA-HRG-0.5 and
SPVA-HRG-1.0. Inset image represents the magnified high frequency part of Nyquist plots; (b) Nyquist
plots of HRG-CCHy in SPVA-HRG-0.5 before and after cycling for 5000 GCD cycles at 2 A g-1.
Inset image represents the magnified high frequency part of Nyquist plots
Conclusion
SPVA-HRG-x were prepared by introducing HRG into SPVA and characterized using XRD
technique. Supercapacitor assembled by using HRG-CCHy and GPEs was characterized by CV, GCD
S. S. Rajaputra et al. J. Electrochem. Sci. Eng. 11(3) (2021) 197-207
http://dx.doi.org/10.5599/jese.1031 205
and EIS. As confirmed by XRD measurements, SPVA-HRG-x may have induced amorphous nature,
improving thereby ionic conductivity and lowering impedance. HRG-CCHy in SPVA-HRG-0.5
exhibited a specific capacitance of 200 F g-1 at 1 A g-1 with the lowest IR drop of around 0.07 V and
an impressive specific energy of 6.1 Wh kg-1 at the specific power of 1 kW kg-1. Even after 5000 GCD
cycles, HRG-CCHy retained 93 % of its initial capacitance in SPVA-HRG-0.5. The notable performance
of HRG-CCHy in SPVA-HRG-0.5 may be attributed to the relatively lower impedance in
SPVA-HRG-0.5. From the performed electrochemical studies, it can be inferred that SPVA-HRG-0.5
can be considered as a potential GPE for application in quasi solid-state flexible supercapacitors.
Acknowledgements: The authors are grateful to Er Koneru Satyanarayana Garu, Hon’ble President, Koneru
Lakshmaiah Education Foundation (Deemed to be University) for in-house funding to carry out this work. The
authors also thank the CoExAMMPC, VFSTR, Guntur, AP for X-ray diffraction (XRD) measurement.
References
[1] J. Liang, B. Tian, S. Li, C. Jiang, W. Wu, Advanced Energy Materials 10 (2020) 2000022.
https://doi.org/10.1002/aenm.202000022
[2] J. Liu, J. Ye, F. Pan, X. Wang, Y. Zhu, Science China Materials 62 (2019) 545-554.
https://doi.org/10.1007/s40843-018-9309-x
[3] J. Ben, Z. Song, X. Liu, W. Lu, X. Liu, Nanoscale Research Letters 15 (2020) 151.
https://doi.org/10.1186/s11671-020-03379-w
[4] A. K. Yedluri, S. Sambasivam, S. A. Hira, K. Zeb, W. Uddin, T. N. V. Krishna, K. D. Kumar, I. M.
Obaidat, H. J. Kim, Electrochimica Acta 364 (2020) 137318.
https://doi.org/10.1016/j.electacta.2020.137318
[5] M. Sandhiya, S. Suresh Balaji, M. Sethish, Energy & Fuels 34(9) (2020) 11536-11546.
https://doi.org/10.1021/acs.energyfuels.0c02199
[6] B. Cai, C. Shao, L. Qu, Y. Meng, L. Jin, Frontiers of Materials Science 13 (2019) 145-153.
https://doi.org/10.1007/s11706-019-0455-2
[7] A..K. Yedluri, S. Singh, P..J..S. Rana, K..D. Kumar, H.-J. Kim, New Journal of Chemistry 44
(2020) 4266-4275. https://doi.org/10.1039/C9NJ06318H
[8] A. K. Yedluri, K. D. Kumar, H.-J. Kim, Dalton Transactions 49 (2020) 3622-3629.
https://doi.org/10.1039/D0DT00268B
[9] A. K. Yedluri, K. D. Kumar, H.-J. Kim, Dalton Transactions 49 (2020) 4050-4059
https://doi.org/10.1039/D0DT00191K
[10] A. K. Yedluri, D. K. Kulurumotlakatla, S. Sangaraju, I. M. Obaidat, H.-J. Kim, Journal of Energy
Storage 31 (2020) 101623. https://doi.org/10.1016/j.est.2020.101623
[11] A. K. Yedluri, K. D. Kumar, H.-J. Kim, Electrochimica Acta 330 (2020) 135261.
https://doi.org/10.1016/j.electacta.2019.135261
[12] G. Zhang, Y. Chen, Y. Chen, H. Guo, Materials Research Bulletin 102 (2018) 391-398.
https://doi.org/10.1016/j.materresbull.2018.03.006
[13] D. Wang, L. Xu, Y. Wang, W. Xu, Journal of Electroanalytical Chemistry 815 (2018) 166-174.
https://doi.org/10.1016/j.jelechem.2018.03.016
[14] X. Chen, R. Paul, L. Dai, National Science Review 4 (2017) 453-489.
https://doi.org/10.1093/nsr/nwx009
[15] D. P. Dubal, N. R. Chodankar, D.-H. Kim, P. R. Gomez, Chemical Society Reviews 47 (2018)
2065-2129. https://doi.org/10.1039/C7CS00505A
[16] S. Alipoori, S. Mazinani, S. H. Aboutalebi, F. Sharif, Journal of Energy Storage 27 (2020)
101072. https://doi.org/10.1016/j.est.2019.101072
[17] Y. Wang, Z. Chang, M. Qian, Z. Zhang, J. Lin, F. Huang, Carbon 143 (2019) 300-308.
https://doi.org/10.1016/j.carbon.2018.11.033
http://dx.doi.org/10.5599/jese.1031
https://doi.org/10.1002/aenm.202000022
https://doi.org/10.1007/s40843-018-9309-x
https://doi.org/10.1186/s11671-020-03379-w
https://doi.org/10.1016/j.electacta.2020.137318
https://doi.org/10.1021/acs.energyfuels.0c02199
https://doi.org/10.1007/s11706-019-0455-2
https://doi.org/10.1039/C9NJ06318H
https://doi.org/10.1039/D0DT00268B
https://doi.org/10.1039/D0DT00191K
https://doi.org/10.1016/j.est.2020.101623
https://doi.org/10.1016/j.electacta.2019.135261
https://doi.org/10.1016/j.materresbull.2018.03.006
https://doi.org/10.1016/j.jelechem.2018.03.016
https://doi.org/10.1093/nsr/nwx009
https://doi.org/10.1039/C7CS00505A
https://doi.org/10.1016/j.est.2019.101072
J. Electrochem. Sci. Eng. 11(3) (2021) 197-207 POLYVINYL ALCOHOL HYDROGEL NANOCOMPOSITE
206
[18] X. Lu, M. Yu, G. Wang, Y. Tong, Y. Li, Energy & Environmental Science 7 (2014) 2160-2181.
https://doi.org/10.1039/C4EE00960F
[19] Y.-G. Cho, C. Hwang, D. S. Cheong, Y.-S. Kim, H.-K. Song, Advanced Materials 31 (2019)
1804909. https://doi.org/10.1002/adma.201804909
[20] M. Rosi, F. Iskandar, M. Abdullah, Khairurrijal, International Journal of Electrochemical
Science 9 (2014) 4251-4256. https://1library.net/document/oy875xwz-hydrogel-polymer-
electrolytes-polyvinyl-alcohol-hydroxyethylcellulose-supercapacitor-applications.html
[21] Q.-M. Tu, L.-Q. Fan, F. Pan, J.-L. Huang, Y. Gu, J.-M. Lin, M.-L. Huang, Y.-F. Huang, J.-H. Wu,
Electrochimica Acta 268 (2018) 562-568. https://doi.org/10.1016/j.electacta.2018.02.008
[22] A. A. Łatoszyńska, P.-L. Taberna, P. Simon, W. Wieczorek, Electrochimica Acta 242 (2017)
31-37. https://doi.org/10.1016/j.electacta.2017.04.122
[23] B. Karaman, A. Bozkurt, International Journal of Hydrogen Energy 43 (2018) 6229-6237.
https://doi.org/10.1016/J.IJHYDENE.2018.02.032
[24] M. Areir, Y. Xu, D. Harrison, J. Fyson, R. Zhang, Materials and Manufacturing Processes 33
(2018) 905-911. https://doi.org/10.1080/10426914.2017.1401712
[25] K. Prasannan, R. Natarajan, S.D. Kaveripatnam, ChemPhysChem 14(16) (2013) 3822-3826.
https://doi.org/10.1002/cphc.201300622
[26] R. Singh, C. C. Tripathi, Materials Today: Proceedings 5 (2018) 1125-1130.
https://doi.org/10.1016/j.matpr.2017.11.192
[27] J. Ye, H. Tan, S. Wu, K. Ni, F. Pan, J. Liu, Z. Tao, Y. Qu, H. Ji, P. Simon, Y. Zhu, Advanced
Materials 30 (2018) 1801384. https://doi.org/10.1002/adma.201801384
[28] Y. L. Li, P. C. Li, B. J. Li, M. K. Gao, F. Y. Zhao, L. Shao, J. F. Chen, L. H. Li, International Journal
of Electrochemical Science 12 (2017) 10567-10576. https://doi.org/10.20964/2017.11.32
[29] D. Ghosh, S.O. Kim, Electronic Materials Letters 11 (2015) 719-734.
https://doi.org/10.1007/s13391-015-9999-1
[30] M. Jiang, J. Zhu, C. Chen, Y. Lu, Y. Ge, X. Zhang, ACS Applied Materials & Interfaces 8 (2016)
3473-3481. https://doi.org/10.1021/acsami.5b11984
[31] K. Sun, M. Dong, E. Feng, H. Peng, G. Ma, G. Zhao, Z. Lei, RSC Advances 5 (2015) 22419-
22425. https://doi.org/10.1039/C4RA15484C
[32] R. Xu, F. Guo, X. Cui, L. Zhang, K. Wang, J. Wei, Journal of Materials Chemistry A 3 (2015)
22353-22360. https://doi.org/10.1039/C5TA06165B
[33] K. Sun, F. Ran, G. Zhao, Y. Zhu, Y. Zheng, M. Ma, X. Zheng, G. Ma, Z. Lei, RSC Advances 6
(2016) 55225-55232. https://doi.org/10.1039/C6RA06797B
[34] G. Ma, M. Dong, K. Sun, E. Feng, H. Peng, Z. Lei, Journal of Materials Chemistry A 3 (2015)
4035-4041. https://doi.org/10.1039/C4TA06322H
[35] H. Gao, K. Lian, Journal of The Electrochemical Society 160 (2013) A505.
https://doi.org/10.1149/2.053303jes/meta
[36] C.-S. Lim, K.H. Teoh, C.-W. Liew, S. Ramesh, Materials Chemistry and Physics 143(2) (2014)
661-667. https://doi.org/10.1016/j.matchemphys.2013.09.051
[37] C.-S. Lim, K. H. Teoh, C.-W. Liew, S. Ramesh, Ionics 20 (2014) 251-258.
https://doi.org/10.1007/s11581-013-0982-2
[38] Y. F. Huang, P. F. Wu, M. Q. Zhang, W. H. Ruan, E. P. Giannelis, Electrochimica Acta 132
(2014) 103-111. https://doi.org/10.1016/j.electacta.2014.03.151
[39] Y. S. Ye, M. Y. Cheng, X. L. Xie, J. Rick, Y. J. Huang, F. C. Chang, B. J. Hwang, Journal of Power
Sources 239 (2013) 424-432. https://doi.org/10.1016/j.jpowsour.2013.03.021
[40] J. Gun, S. A. Kulkarni, W. Xiu, S. K. Batabyal, S. Sladkevich, P. V. Prikhodchenko, V. Gutkin, O.
Lev, Electrochemistry Communications 19 (2012) 108-110.
https://doi.org/10.1016/j.elecom.2012.03.025
https://doi.org/10.1039/C4EE00960F
https://doi.org/10.1002/adma.201804909
https://1library.net/document/oy875xwz-hydrogel-polymer-electrolytes-polyvinyl-alcohol-hydroxyethylcellulose-supercapacitor-applications.html
https://1library.net/document/oy875xwz-hydrogel-polymer-electrolytes-polyvinyl-alcohol-hydroxyethylcellulose-supercapacitor-applications.html
https://doi.org/10.1016/j.electacta.2018.02.008
https://doi.org/10.1016/J.IJHYDENE.2018.02.032
https://doi.org/10.1080/10426914.2017.1401712
https://doi.org/10.1016/j.matpr.2017.11.192
https://doi.org/10.1002/adma.201801384
https://doi.org/10.20964/2017.11.32
https://doi.org/10.1007/s13391-015-9999-1
https://doi.org/10.1021/acsami.5b11984
https://doi.org/10.1039/C4RA15484C
https://doi.org/10.1039/C5TA06165B
https://doi.org/10.1039/C6RA06797B
https://doi.org/10.1039/C4TA06322H
https://doi.org/10.1149/2.053303jes/meta
https://doi.org/10.1016/j.matchemphys.2013.09.051
https://doi.org/10.1007/s11581-013-0982-2
https://doi.org/10.1016/j.electacta.2014.03.151
https://doi.org/10.1016/j.jpowsour.2013.03.021
https://doi.org/10.1016/j.elecom.2012.03.025
S. S. Rajaputra et al. J. Electrochem. Sci. Eng. 11(3) (2021) 197-207
http://dx.doi.org/10.5599/jese.1031 207
[41] Y. C. Cao, C. Xu, X. Wu, X. Wang, L. Xing, K. Scott, Journal of Power Sources 196 (2011) 8377-
838. https://doi.org/10.1016/j.jpowsour.2011.06.074
[42] X. Yang, F. Zhang, L. Zhang, T. Zhang, Y. Huang, Y. Chen, Advanced Functional Materials 23
(2013) 3353-3360. https://doi.org/10.1002/adfm.201203556
[43] S. S. Rajaputra, N. Pennada, A. Yerramilli, N. M. Kummara, Ionics (2021)
https://doi.org/10.1007/s11581-021-04144-4
[44] S. S. Rajaputra, N. Pennada, A. Yerramilli, N. M. Kummara, Journal of Electrochemical
Energy Conversion and Storage 18(4) (2021) 041008. https://doi.org/10.1115/1.4051143
[45] H. Wang, H. Yi, X. Chen, X. Wang, Journal of Materials Chemistry A 2 (2014) 3223-3230.
https://doi.org/10.1039/C3TA15046A
[46] A. Hany, M. A. Mousa, T. El-Essawy, Journal of Basic and Environmental Sciences 4 (2017)
298-304. https://jbesci.org/published/4.4.2.pdf
[47] E. Sheha, M. K. El-Mansy, Journal of Power Sources 185 (2008) 1509-1513.
https://doi.org/10.1016/j.jpowsour.2008.09.046
[48] Y. Pavani, M. Ravi, S. Bhavani, A. K. Sharma, V. V. Narasimha Rao, Polymer Engineering &
Science 52 (2012) 1685-1692. https://doi.org/10.1002/pen.23118
[49] R. M. Hodge, G. H. Edward, G. P. Simon, Polymer 37 (1996) 1371-1376.
https://doi.org/10.1016/0032-3861(96)81134-7
[50] K. Ghosh, C. Y. Yue, Electrochimica Acta 276 (2018) 47-63.
https://doi.org/10.1016/j.electacta.2018.04.162
[51] M. P. Kumar, T. Kesavan, G. Kalita, P. Ragupathy, T. N. Narayanan, D. K. Pattanayak, RSC
advances 4 (2014) 38689-38697. https://doi.org/10.1039/C4RA04927F
[52] X. Lu, Y. Zeng, M. Yu, T. Zhai, C. Liang, S. Xie, M. S. Balogun, Y. Tong, Advanced Materials 26
(2014) 3148-315.5 https://doi.org/10.1002/adma.201305851
[53] J. Cao, C. Chen, K. Chen, Q. Lu, Q. Wang, P. Zhou, D. Liu, L. Song, Z. Niu, J. Chen, Journal of
Materials Chemistry A 5 (2017) 15008-15016. https://doi.org/10.1039/C7TA04920J
[54] N. Deka, J. Deka, G. K. Dutta, Chemistry Select 3 (2018) 8483-8490.
https://doi.org/10.1002/slct.201801507
[55] S. P. S. Moopri, G. K. Veerasubramani, R. M. Bhattarai, G. Gnanasekaran, S. J. Kim, Y. S.
Mok, ACS Applied Energy Materials 4 (2021) 2218-2230.
https://doi.org/10.1021/acsaem.0c02739
[56] H. Yu, J. Wu, L. Fan, K. Xu, X. Zhong, Y. Lin, J. Lin, Electrochimica Acta 56 (2011) 6881-6886.
https://doi.org/10.1016/j.electacta.2011.06.039
[57] Q. Chen, X. Li, X. Zang, Y. Cao, Y. He, P. Li, K. Wang, J. Wei, D. Wu, H. Zhu, RSC Advances 4
(2014) 36253-36256. https://doi.org/10.1039/C4RA05553E
[58] G. Radić, I. Šajnović, Ž. Petrović, M. Kraljić Roković, Croatica Chemica Acta 91(4) (2018)
481-490. https://doi.org/10.5562/cca3452
[59] S. T. Senthilkumar, R. K. Selvan, N. Ponpandian, J. S. Melo, Y. S. Lee, Journal of Materials
Chemistry A 1 (2013) 7913-7919 https://doi.org/10.1039/C3TA10998D
[60] X. Liu, C. Men, X. Zhang, Q. Li, Liu, Small 12 (2016) 4973-4979
https://doi.org/10.1002/smll.201600841
©2021 by the authors; licensee IAPC, Zagreb, Croatia. This article is an open-access article
distributed under the terms and conditions of the Creative Commons Attribution license
(https://creativecommons.org/licenses/by/4.0/)
http://dx.doi.org/10.5599/jese.1031
https://doi.org/10.1016/j.jpowsour.2011.06.074
https://doi.org/10.1002/adfm.201203556
https://doi.org/10.1007/s11581-021-04144-4
https://doi.org/10.1115/1.4051143
https://doi.org/10.1039/C3TA15046A
https://jbesci.org/published/4.4.2.pdf
https://doi.org/10.1016/j.jpowsour.2008.09.046
https://doi.org/10.1002/pen.23118
https://doi.org/10.1016/0032-3861(96)81134-7
https://doi.org/10.1016/j.electacta.2018.04.162
https://doi.org/10.1039/C4RA04927F
https://doi.org/10.1002/adma.201305851
https://doi.org/10.1039/C7TA04920J
https://doi.org/10.1002/slct.201801507
https://doi.org/10.1021/acsaem.0c02739
https://doi.org/10.1016/j.electacta.2011.06.039
https://doi.org/10.1039/C4RA05553E
https://doi.org/10.5562/cca3452
https://doi.org/10.1039/C3TA10998D
https://doi.org/10.1002/smll.201600841
https://creativecommons.org/licenses/by/4.0/)