Silicon dioxide

Journal Pre-proof Synthesis, characterization and supercapacitor application of ionic liquid incorporated nanocomposites based on SPSU/Silicon dioxide Seyda Tugba Gunday, Emre Cevik, Abdulmalik Yusuf, Ayhan Bozkurt PII:

S0022-3697(18)33195-0

DOI:

https://doi.org/10.1016/j.jpcs.2019.109209

Reference:

PCS 109209

To appear in:

Journal of Physics and Chemistry of Solids

Received Date: 11 December 2018 Revised Date:

9 September 2019

Accepted Date: 17 September 2019

Please cite this article as: S.T. Gunday, E. Cevik, A. Yusuf, A. Bozkurt, Synthesis, characterization and supercapacitor application of ionic liquid incorporated nanocomposites based on SPSU/Silicon dioxide, Journal of Physics and Chemistry of Solids (2019), doi: https://doi.org/10.1016/j.jpcs.2019.109209. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

Synthesis, characterization and supercapacitor application of ionic liquid incorporated nanocomposites based on SPSU/Silicon dioxide Seyda Tugba Gunday1, Emre Cevik2, Abdulmalik Yusuf 3, Ayhan Bozkurt1,* 1

Department of Physics, IRMC, Imam Abdulrahman Bin Faisal University, 1982, Dammam,

31441, Saudi Arabia. 3

Department of Genetics Research, IRMC, Imam Abdulrahman Bin Faisal University, PO

Box:1982, Dammam, 31441, Saudi Arabia 3

Independent Researcher, C. Cunca 6, Parla, 28982, Madrid, Spain.

*Corresponding author. e-mail: [email protected]

Abstract In this study, we report about novel polymer electrolytes containing sulfonated polysulfone (SPSU) as the polymer matrix, silicon dioxide (SiO2) as nano additive and ionic liquid (1Ethyl-3-methyl-imidazolium tetrafluoroborate) IL) as a softening agent. In addition, the physical and chemical properties of ionic liquid containing nanocomposite gel polymer electrolytes were studied and subsequently the optimized electrolyte was used to assemble the supercapacitor device. Nanocomposite gel polymer electrolytes demonstrated higher thermal stability and lower glass transition temperatures (Tg) required for supercapacitor application. The ion conductivity of the nanocomposite polymer electrolytes was investigated using a dielectric-impedance analyzer at various temperatures. The highest conductivities were obtained for the samples SPSU/0.1IL and SPSU/%3n SiO2/0.2IL with values 3.1 x10-4 and 3.2 x10-3 S cm−1 at 100 °C, respectively. In addition, symmetrical cell formation based on Al/C/SPSU/%3nSiO2/0.2IL/C/Al showed a maximum specific capacitance of 134.1 F g-1 at 1 A g-1. The same cell also yielded a maximum energy density in supercapacitor as 18.6 Wh kg−1 at a power density of 1089 W kg-1. 1

Keywords: Silicon dioxide nanoparticles, Sulfonated Polysulfone, supercapacitors, ionic liquid, ion conductivity.

1. Introduction Owing to the growing global energy crisis, more alternatives are being sought to storage energy supplied by intermittent supply, such as solar energy from renewable sources. Energy storage devices such as supercapacitors have become more important because they provide faster energy and have a longer cycle life than batteries [1]. These devices are fabricated by sandwiching an ion-conducting electrolyte between various electrode combinations [2, 3]. The supercapacitors have higher power density than conventional capacitors, and lower energy density than lithium-ion batteries [4-6]. In addition, they provide rapid charging and discharging at power densities above 1000 W kg−1 due to their efficient reversible charge storage mechanism [7, 8]. Recently, the application of supercapacitors in consumer electronics, industrial power management and hybrid electric vehicles has increased greatly due to the aforementioned features [9-11]. However, there are still obstacles such as electrochemical stability, operating windows, and short life that limit their wider practical applications. The fine-tuning of these properties depends essentially on the most advanced organic and aqueous electrolytes. In addition, other issues such as toxicity, volatility and flammability of organic electrolytes pose a threat to human life and the environment. Gel polymer electrolytes are one of the most promising candidates to solve these problems due to the following advantages; environmentally safe handling without leakage, ease of manufacture, flexible packaging and reduced internal corrosion, etc.[12, 13]. Furthermore, in gel polymer electrolytes ILs have been recognized as potential substitutes for organic solvents, and have received great interest within scientific community [14, 15]. ILs are typical

2

organic salts which are of great importance due to their properties such as electrochemical windows, ionic conductivity (10-3-10-2 S cm-1), flammability and better thermal stability. [16, 17]. In addition, they can be tailored for different requirements such as electrolyte materials for supercapacitors, batteries, fuel cells [18]. For instance, 1 methyl 3 ethyl imidazolium tetracycanoborate intercalated in poly vinylidenefluoride co hexafluoropropylene (PVDF co HFP) polymer yielded an ionic conductivity of 9 x10-3 S cm−1 at ambient temperature [19].

Furthermore,

1 ethyl 3 methylimidazolium

thiocyanate

was

inserted

into

polyacrylonitrile and this gel electrolyte was illustrated a high conductivity around 1 x 10-2 S cm−1. The fabricated supercapacitor including this electrolyte was very stable and produced 2000 cycles [20] . Similarly, 1 ethyl 3 methylimidazolium tetrafluoroborate or 1 ethyl 3 methylimidazolium bis(trifluoromethylsulfonyl)imide was entrapped into polymer, PVDF co HFP with an inorganic additive to prepare soft electrolyte with improved cycle number and performance [21, 22].

Alternatively, sulfonated polysulfone (SPSU) can be produced by chemical sulfonation of polysulfone (PS) which displays a better thermal and chemical stability as well as high mechanical property [23]. SPSU can be suggested for utilization in energy devices such as supercapacitors, after incorporation of suitable additives such as softening agents and nanoparticles. Silicon dioxide (SiO2) also known as silica, is a commonly occurring material in nature. There are many known crystalline and non-crystalline silica minerals of inorganic and biogenic origin. Different crystalline modification of silica can form depending on pressure, temperature, composition of the precursor phases, etc. Quartz is the most abundant and wellknown polymorph. Quartz sand and silica rocks are vastly utilized as raw materials for ceramics, glass, and silicon production in industry. Both natural and synthetic silica powders

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are utilized as fillers to improve the mechanical properties of materials [24]. An interesting approach was the incorporating hydrophilic metal oxide particles such as silicon oxide or titania into a ion conducting polymer to improve the corresponding conductivity, mechanical property as well as water retention capability under different operating conditions [25].

Silica nanoparticles have attracted high interest in scientific research, due to their ease of synthesis and their vast potential applications in several fields like pigments, electronics, pharmacy, catalysis, electronic and thermal insulators, and humidity sensors [26, 27].

In this study, ionic liquid incorporated gel polymer electrolyte systems based on SPSU and SiO2 nanoparticles were prepared. In order to achieve a better compromise between properties like conductivity, homogeneity, as well as dimensional stability, the gel polymer electrolytes were prepared with different additive concentrations. The characterizations of the gel polymer electrolyte were performed via FT-IR, SEM, DSC, and TGA techniques. To investigate the ionic conductivity property of the gel polymer electrolytes, the Novocontrol dielectricimpedance analyzer was employed. Furthermore, galvanostatic charge-discharge and cyclic voltammetry (CV) techniques were employed to study the electrochemical performance of the fabricated supercapacitor. 2. Experimental 2.1. Chemicals The commercial polysulfone (PSU), Methyl sulphate sodium salt, Hydrochloric acid (HCl ACS reagent, 37%), Aluminum oxide nanoparticles, methanol, and trimethylsilyl chlorosulfonate

(TMSCS)

were

purchased

from

Sigma-Aldrich,

1-Ethyl-3-methyl-

imidazolium tetrafluoroborate ≥ 97% was merchandised Fluka. Timical super C65 application: as conductive additive, Kuraray active carbon for supercapacitor electrode, and HSV 900 polyvinylidene fluoride binder for Li-ion battery electrodes and were obtained MTI. 4

N,N-Dimethyl acetamide (DMAc), 1,2-dichloroethane (DCE), 1-Methyl-2-pyrrolidone (NMP) were purchased Merck. 2.2. Preparation

The polymer was dissolved in DCE at 25 °C for 4h over N2 gas to provide sulfonation of PSU [28]. During the reaction, TMSCS was used as a sulfonating agent with the mole ratio of PSU:TMSCS; 1:1.5. In order to eliminate the HCl through the reactor, the reaction medium was continuously purged with nitrogen. After 36 h, the reaction was quenched to cleave the silyl sulfonate moieties and then methanol was added to the solution yielding SPSU. Evaporation process was performed at 1 atm to eliminate methanol, water, dichloroethane, methyl sulfate, and silicon-containing compounds. The material was further dried at 50 °C under vacuum. This is followed by calculation of the sulfonation ratio of SPSU which was carried out by titrimetric method.

The sulfonation ratio was found to be 104% [(mol

SO3H/repeat unit) × 100], which was close to that reported sulfonation level [28]. A grinding miller was employed to obtain SPSU powder that is necessary for

preparing the

nanocomposites (Scheme 1).

Scheme 1. The polymeric gel films of SPSU / Silicon dioxide nanoparticles / IL composed of different ratios were prepared by the solution-casting method. Initially, 0.2 g of the host polymer SPSU was dissolved in 15 mL of dimethylacetamide (DMAc). After that, nSiO2 and IL were added to the SPSU/ DMAc solution. The prepared film compositions are given in Table 1. The resultant mixture was mechanically mixed on a magnetic stirrer for 30 min. at 80°C, and subsequently it was sonicated in an ultrasonic bath for 30 min. in order to attain a homogenous viscous appearance.

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Table 1

Finally, the material were cast onto polytetrafluoroethylene/teflon petri-dish and dried at room temperature and finally at 65 °C for 24 h under vacuum.

2.3. Electrode Preparation Scheme 2.

The compositions of the electrodes used in fabrication of the supercapacitor consisted of 10% (w/w) conductive carbon (CC), 10% (w/w) PVDF and 80% (w/w) active carbon (CA). Initially, PVDF was dissolved in NMP at 70 °C and then carbon black and active carbon were slowly admixed [29]. The resulting slurry was stirred (400 rpm) for 5 hours at 75 °C and then further mixed at room temperature. Subsequently, the carbon slurry was cast on aluminum mesh current collectors by automatic coating machine (MRX Shenzhen Automation Equipment) with a thickness of 10 µm. After the coating, the electrodes were dried at 70 °C, in a standard oven (Scheme 2). Consequently, the electrodes were cut using Hi-Throughput Precision Pneumatic Disk Cutter with die size 15 mm. All the electrodes have the same surface area with the same mass of active material (1 mg) deposited on each electrode. 2.4. Instrumentation and Experimental Variables

FT-IR spectra of the samples were obtained using Bruker Alpha-P in ATR system between 4000-400 cm-1. Thermal stability of the nanocomposite gel polymer electrolytes was evaluated using PerkinElmer Pyris 1 TG Analyzer. Samples were heated between 25 °C and 700 °C in N2 medium at a scanning rate of 10 °C min-1. DSC analysis was performed using

6

the HITACHI DSC 7000X instrument under nitrogen atmosphere with a scan rate of 10 °C min-1.

Ion conductivity of the nanocomposite polymer electrolytes was studied by Novocontrol dielectric-impedance analyzer as a function of temperature under dry N2 atmosphere, frequency range was 0.1 Hz to 3 MHz.

Supercapacitor devices were fabricated using the configuration of Carbon/polymer electrolyte/carbon. The device has a combination SPSU/%3n SiO2/0.2IL showed a maximum ionic conductivity which used as an electrolyte in the supercapacitors. The Swagelok cell kit was used to make all electrochemical analysis of the cell configuration of the supercapacitor.

Cyclic voltammetry (CV) studies of the devices were investigated by using Palmsens emstat 4 electrochemical analyzer. The S5 electrolyte placed in supercapacitor cell was then subjected to CV and galvanostatic charge discharge. The cell was held for 5 seconds before CV measurement, connected to the MTI Battery Analyzer with a current density of 1 to 10 A g-1 and cut the voltage range of 0.1 and 1 V.

The specific discharge capacitance (Cs) was calculated from the charge–discharge curves, according to the following equation; Cs=2 I ∆t/ w ∆V

(1)

where I is the discharge current, w is the mass of the electrode, ∆t is the discharge time and ∆V is the voltage difference in discharge process[30]. The energy density and the power density values of the fabricated supercapacitor were determined from the galvanostatic charge-discharge data according to Eq. 2 & Eq. 2 [31]. E= ½ × Cs × (∆V 2)/3.6

(2) 7

P= E × (3600/∆t)

(3)

The surface morphology of the prepared composite electrodes was investigated by scanning electron microscopy (SEM) (FEI, Inspect S50). The samples were coated with gold and examined under SEM at different magnifications with an accelerating voltage of 20 kV.

3. Results and Discussion Fig. 1.

Fig. 1a shows the FT-IR spectra of the silicon dioxide NPs based nanocomposite polymer electrolytes; The peaks at 690, 1041, 1149 and 1236 cm-1 belong to SPSU [32]. The shifted stretching C-H vibration peaks of imidazolium ring and in plane deformation vibrations of EMImBF showed peaks at 3050 cm-1 and 1300 cm-1, respectively. The C=C bonds in EMImBF4 exhibited peak at 1600 cm-1. Finally, the peak at around 1150 cm-1 was attributed to Si-O-Si bond of SiO2 [33]. The intensity of the corresponding peaks increased with their contents in the nanocomposite polymer electrolytes.

The TGA curves of the SPSU/IL/SiO2 films illustrated decomposition patterns as illustrated in Fig.1b. The desorption of free water bonded form the hydrophilic sulfonic groups produced a slight mass loss between 50 °C and 250 °C for SPSU and SPSU/IL. However, the composite membranes (SPSU/IL/SiO2) illustrated no weight change at low temperature domain and an improvement in the thermal stability of these sulfonic acid groups due to the insertion of 3-5 wt% of SiO2 nanoparticles. The shift of this temperature can be attributed to the interaction of this inorganic oxide and polysulfone which limits the segmental motions of polymer chains [34]. In the range of 280- 318 °C, all the samples illustrated a remarkable weight change due to desulfonation process, which may involve the removal of SO and SO2 gases. Thus, the onset of the degradation temperature corresponding to desulfonation process was 255 °C, 250

8

°C, and 258 °C for SPSU/%5SiO2/0.2IL, SPSU/%5SiO2/0.1IL and SPSU/%3SiO2/0.2IL, respectively. For these series, weight change up to their decomposition temperatures slightly increased with increasing SiO2 nanoparticles. The second intense weight loss, which started at 318 °C and ended 420 °C, can be attributed to the polymer backbone decomposition as well as degradation of IL. The final weight loss above 425 °C is due to further degradation of the polymer and additives [35].

Fig. 1c shows the DSC curves of SPSU/IL and SPSU/SiO2/IL based gel polymer electrolytes. The DSC measurements were conducted by subjecting the samples to two heating and one cooling processes. Here, the second heating process with the same rate was evaluated. The glass transition temperature (Tg) of pure SPSU was measured to be 76 °C. The Tgs of the samples SPSU/0.1IL, SPSU/%3SiO2/0.2IL and SPSU/%5SiO2/0.2IL were measured as -35 °C, -33 °C and -28 °C, respectively. As seen, the Tg of all the samples moved to lower temperatures showing the strong plasticizing effect of IL. Among the composite series, a slight shifting of Tg to higher temperature was noticed with increasing the SiO2 content. However, no Tg was detected for SPSU/%5SiO2/0.1IL which may be due to low concentration of IL in the composite electrolyte.

Fig. 2. The dielectric-impedance analyzer was employed to determine the AC ionic conductivity of gel polymer electrolytes. The measurement carried out in the frequency range between 1 Hz to 3 MHz as a function of temperature (20 °C - 100 °C). The diameter of the film samples had an average of 9.5 mm and an average thickness of 0.3 mm. To measure the temperaturedependent ionic conductivities, the samples were sandwiched in between two platinum blocking electrodes.

9

The AC conductivities (ϭac (ω)) of the samples were measured at different temperatures according to equation (4); ϭˈ(ω) = ϭac (ω) = ɛ ̎ (ω) ω ɛ0

(4)

Where the values ϭˈ(ω) is the real part of the conductivity, ω=2πf is the angular frequency, ɛo is vacuum permittivity and ε̎ is imaginary part of complex dielectric permittivity (ɛ*). [36]

Fig. 2a and 2b show the frequency dependent AC conductivities of nano silica containing SPSU based gel polymer electrolytes. Moreover, Table 2 shows the maximum ionic conductivity values of the samples at 30 °C and 100 °C. Based on AC conductivity graphs, different regions are observed within the measured frequency range. At low frequency (f < 104), a decrease in AC conductivity is observed, which is attributed to the polarization of the electrodes, while at high-frequency, the AC ionic conductivity is independent of frequency. The data from the plateau region of the AC were linear fitted in order to derive the DC ionic conductivities [37, 38], according to Eq. 5, where ϭ (0) is the DC conductivity and A and n are constants. ϭˈ(ω) = ϭ (0) +A ωn

(5)

Table 2. The DC conductivity versus temperature curves of nanocomposite polymer electrolytes are provided in Fig. 2c. The curvature in the lines can be interpreted by Vogel-Tamman-Fulcher (VTF) model [39];

logσ = logσo–Ev/[k (T−To)]

(6)

10

where the value, σo is the conductivity at infinite temperature, Ev is the vogel activation energy and To is the Vogel temperature (Table 2). All the curves can be described by the VTF equation except SPSU/%3SiO2/0.2IL which showed almost linear behavior. This trend can be expressed by the presence of less inorganic additive and relatively high IL where ion diffusion can occur over liquid phase. The ionic conductivity of 2.6 x 10-4 S cm−1 at 30 °C and 3.2 x10-3 S cm−1 and at 100 °C was achieved for the SPSU/%3nSiO2/0.2IL. Both inorganic additive and IL increased ionic conductivity of the electrolyte, SPSU/%3nSiO2/0.2IL. A decrease in the ionic conductivity was observed with further increase in the amount of SiO2 while keeping the ionic liquid amount constant. The enhancement of ionic conductivity is attributed to the synergistic effect of both ionic liquid and nano silica. The strong plasticizing effect of the ionic liquid, which softens the polymer backbone, coupled with the high affinity of SiO2 nanoparticles to the ionic liquid. It has been reported that Lewis acid groups on the surfaces of SiO2 nanoparticles can interact with ionic species in the electrolyte, resulting in higher ionic conductivities [40, 41] Furthermore, the softening of the polymer matrix could increase the charge carriers (ions) dissociation by weakening the coordinative bonds and hence result in fast ionic conduction. The physicochemical properties of the ionic liquid, i.e. high dielectric constant and low viscosity seemed to be the main contributing factor for the increased ionic conductivity in the gel polymer electrolytes [42, 43].

Fig. 3. Cyclic voltammetry was used to investigate the electrochemical properties of fabricated devices, including all ionic liquid based polymer electrolytes. CV measurements were performed in a stable electrochemical potential window of 0.0 and 1.0 V, and the best performance was obtained from the SPSU/3%nSiO2/0.2IL gel polymer electrolyte-based 11

supercapacitor. CV measurements of the SPSU/3%nSiO2/0.2IL supercapacitor were shown at different scan rates ranging from 10 to 400 mV s-1 (Fig. 3a). The black line shows the cyclic voltammogram obtained at a scan rate of 10 mV s-1. The trend of the curve shows that indicate that the current density increased with the increased scan rate. This phenomenon can be explained by the fast ion transfer capability of the gel polymer electrolyte SPSU/%3nSiO2/0.2IL and also due to the rapid ion diffusion within the electrodes of the supercapacitor. Moreover, this behavior was retained even at high scan rates of 400 mV s-1 by the SPSU/%3nSiO2/0.2IL based supercapacitor indicating a high electrochemical capability. In Fig. 3b a good linear relationship was observed between the anodic (Ipa) and cathodic (Ipc) peak current vs. square root of the scan rate. The linear relationship between the peak currents, Ipa - Ipc, and the square root of scan rate was attributed to a charge dispersion in the gel polymer electrolyte which occurs via a diffusion process like counter-ion motion. Furthermore, based on the observed increase of the Ipa and Ipc with increasing scan rate, the charge propagation can be said to be a diffusion-controlled process. Fig. 4. The galvanostatic charge-discharge technique was employed to investigate the capacitance parameters of the fabricated supercapacitor. The data reported in Fig. 4a and b corresponds to SPSU/%3nSiO2/0.2IL based supercapacitor. The rate capability of the fabricated supercapacitor was evaluated by applying different current densities in a range of 1 - 10 A g-1 as shown in Fig. 4a. The charge and discharge time were observed to decrease at high current density. When the current density was increased from 1 A g-1 to 10 A g-1 only 15% of the specific capacitance of the supercapacitor was lost from 134.1 F g-1 to 105.2 F g-1 (Fig. 4c), which indicates a high rate capability. The chargedischarge cycles of the fabricated supercapacitor at a current density of 1 A g-1 is shown in Fig. 4b. The cycling charge-discharge results indicate the supercapacitor based on the 12

SPSU/%3nSiO2/0.2IL gel polymer electrolyte showed a better electrochemical performance and its capacitance values are comparable with other reported results [44].

Fig. 5. The charge-discharge test was also used to evaluate the operational stability of the SPSU/%3nSiO2/0.2IL based supercapacitor. A current density of 1 A g-1 was applied to the same cell and the measurements repeated. The capacitance retention behavior of the fabricated supercapacitor after 10.000 cycles was demonstrated in Fig. 5a. The supercapacitor retained about 80% of its initial capacitance after 5.000 charge discharge cycles, indicating that the SPSU/%3nSiO2/0.2IL based supercapacitor had excellent performance. Power density and energy density are important parameters used to determine the performance of supercapacitors. The power output with the maximum efficiency provided by the supercapacitor device is illustrated by the Ragone plot (Fig. 4b). The maximum energy density of 18.6 Wh kg−1 at a power density of 1089 W kg−1 was obtained from the SPSU/%3n SiO2/0.2IL based supercapacitor. The energy density generally decreases with increasing power density[29]. This might be explained by the ion transfer limitation through the double layer formation within carbon-based electrodes. Similar results were reported with symmetrical supercapacitors by different research groups[45, 46]. It was observed that the energy density decreased with the increase in energy density. The lowest energy density of ~14.5 Wh kg−1 was determined at a power density of ~10.500 W kg-1, which indicates an excellent performance retention. Fig. 6. Fig. 6a and 6b show the SEM images of CC/CA/PVDF slurry coated electrode with two different magnifications i.e., 30 µm and 100 µm respectively. The microstructures indicate 13

that the electrode consists of particles which are dispersed homogeneously within the binder and also having a very rough surface. Moreover, Fig. 6c and 6d shows the coated layer of the electrolyte on the electrode, the surface roughness also decreased significantly. It is seen a rapid capacitance loss of around 5000 cycles of the capacitor is observed. Due to that reason the supercapacitor device was disassembled after 5000 cycles. A detailed surface analysis showed the microstructure remained almost the same, but some cracks appeared, which may be due to the expansion of the electrode material during the cycling (Fig. 6e and 6f). This morphological change is expected to affect the charge store capability of the device and may cause a rapid loss of capacitance after 5.000 cycles as shown in Figure 5a. Conclusions Ionic liquid incorporated SPSU/SiO2 based gel polymer electrolytes were prepared and their composition dependent properties were investigated. Thermal measurements indicated that the materials have good thermal stability and the addition of IL shifted the Tg to lower temperatures. The maximum ionic conductivity of 3.2 x10-3 S cm−1 was measured for SPSU/%3nSiO2/0.2IL at 100 oC. No redox peak from a faradaic current was noticed in the cyclic voltammetry plot of the fabricated supercapacitor, which confirmed EDLC formation. The nearly linear curves of the charge/discharge plots indicated an excellent efficiency with an electrochemical reversibility up to 5000 cycles. A specific capacitance of 134.1 F g-1 at 1 A g-1 was yielded for the device containing SPSU/%3nSiO2/0.2IL gel polymer electrolyte. Moreover, a maximum energy density of 18.6 Wh kg−1 at a power density of 1089 W kg-1 was calculated for the device. The elucidated properties of the gel polymer electrolyte confirmed its suitability for use in supercapacitor applications. Acknowledgement This study was partially supported by Institute for Research and Medical Consultations, (IRMC) - IAU. 14

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TABLES

Table 1 Compositions of Silicon dioxide nanoparticles based nanocomposite electrolytes. Sample

SPSU

nSiO2 Silicon dioxide

Ionic Liquid -IL

nanoparticles (W%) SPSU/ 0.1IL

0.2g

0.1g

SPSU/%5 nSiO2/0.1IL

0.2g

5%

0.1g

SPSU/%3 nSiO2/0.2IL

0.2g

3%

0.2g

SPSU/%5 nSiO2/0.2IL

0.2g

5%

0.2g

Table 2. Maximum ion conductivity values for Silicon dioxide nanoparticles nanoparticles based nanocomposite electrolytes at 30 °C and 100 °C. Sample

Maximum ion conductivity

Maximum ion conductivity

(S cm-1) at 30 °C

(S cm-1) at 100 °C

SPSU/0.1IL

2 x 10-5

2.55 x10-4

SPSU/%5nSiO2 /0.1IL

1.12x10-5

2.76x10-5

SPSU/%3nSiO2 /0.2IL

2.60x10-4

2.40x10-3

SPSU/%5nSiO2 /0.2IL

1.70x10-4

1.26x10-3

18

Figures and Captions

Scheme 1. Synthesis of Sulfonated Polysulfone (SPSU).

Scheme 2. Supercapacitor preparation steps.

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Fig. 1. a) FT-IR spectra of the electrolytes b) TGA curves of SPSU/IL and SiO2 including nanocomposite electrolytes c) DSC curves of all electrolytes.

20

Fig. 2. a) AC conductivity (S cm-1) versus Frequency (Hz) of SPSU/%3nSiO2/0.2IL nano composite electrolyte at various temperatures b) AC conductivity (S cm-1) versus Frequency (Hz) of SPSU/%5nSiO2/0.2IL nano composite electrolyte at various temperatures. c) Temperature dependence of the DC conductivities of SiO2 nanoparticles based nanocomposites polymer electrolytes.

21

Fig. 3. a) Cyclic voltammetry voltammogram of SPSU/%3nSiO2/0.2IL in different scan rates, b) Specific representation of scan rates (mV s-1) vs current (mA) obtained from SPSU/%3nSiO2/0.2 IL.

22

Fig. 4. a) Charge-discharge curves of SPSU/%3nSiO2/0.2IL b) Charge-Discharge cycles of SPSU/%3nSiO2/0.2IL at 1 A g-1 c) Specific capacitance of SPSU /%3n SiO2/0.2 IL.

23

Fig. 5. a) Capacitance retention of SPSU/%3nSiO2/0.2IL up to 10.000 cycle b) Energy and power density of the supercapacitor.

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Fig. 6. a) and b) SEM images of carbon slurry coated Aluminum in different scales, c) and d) SEM images obtained after coating of SPSU/%3nSiO2/0.2 IL in different scales, e) and f) SEM images after 5.000 cycle charge-discharge operation of the supercapacitor in different scales 25

Highlights A series of SPS/SiO2 /IL based nanocomposite polymer electrolytes was produced. In anhydrous state the highest ionic conductivity of SPSU/%3n SiO2/0.2 IL was measured as 3.2 x10-3 S cm−1 Supercapacitor with a configuration Al/C/SPSU/%3nSiO2/0.2IL/C/Al was assembled. The device exhibited a specific capacitance of 134.1 F g-1 at 1 A g-1

Dear Editor

1) This material has not been published in whole or in part elsewhere; 2) The manuscript is not currently being considered for publication in another journal; 3) All authors have been personally and actively involved in substantive work leading to the manuscript, and will hold themselves jointly and individually responsible for its content. Yours Sincerely, Prof Dr Ayhan Bozkurt