Structural, Optical, and Electrical Studies of PAN-Based Gel Polymer Electrolytes for Solid-State Battery Applications

Abstract

Gel polymer electrolyte films (GPEs) based on polyacrylonitrile (PAN) complexed with NaF salt and an Al2O3 nanofiller were prepared via solution cast method. Structural studies were performed to investigate the order of conductivity under the influence of salt and nanofillers. The prepared films were characterized using energy dispersive x-ray spectrometry (EDS) to determine the chemical composition in wt%. EDS studies reveal that PAN–NaF with Al2O3 ceramic filler decreases the degree of crystallinity with increasing concentration of the nanofiller. The UV–Vis spectrum was recorded by a Hewlett-Packard HP8452A diode array spectrometer. The structural effect of salt and nanoparticles on the conductivity was also confirmed by UV–Vis spectroscopy. The mechanical properties of the prepared polymer electrolytes were determined using a Universal Tensile Machine (Instron Model 5565, Canada) with a constant crosshead speed of 10 mm/min. The addition of nanoparticles increased both the modulus and the strength of the polymer nanocomposites. Both the tensile strength and Young’s modulus increased with increasing functionalized nanoparticle loading. The change in transition temperature caused by the incorporation of the Al2O3 nanofiller and plasticizer into the PAN+NaF complex was studied by differential scanning calorimetry (DSC) analysis. Additionally, DSC thermograms were recorded to measure the glass transition temperature and melting temperature of PAN-based electrolytes using a Mettler instrument. Conductivity studies were carried out for all the prepared polymer electrolytes to understand the conduction mechanism. The role of the ceramic phase is to reduce the melting temperature, which is ascertained from DSC. The sample containing PAN:NaF (70:30) exhibits the highest conductivity of 1.82 x 10−4 S cm−1 at room temperature (303 K) and 2.96 x 10−3 S cm−1 at 378 K. The polymer electrolytes considered in the present study exhibited an Arrhenius type of conduction. The polymer electrolyte containing 3 wt% Al2O3 nanofiller showed an ionic conductivity of 5.96 × 10−3 S cm−1. To determine transfer numbers, Wagner’s polarization method can be used. From these studies, it is observed that the conduction mechanism is predominantly due to ions. Using this (PAN–NaF– Al2O3) (70:30:3) electrolyte, a solid-state electrochemical cell was fabricated, and its discharge profiles were studied under a constant load of 100 kΩ. Finally, several cell profiles associated with this cell were evaluated and reported.

1. Introduction

For the last three decades, ionic solid conducting polymer electrolytes have been used as active potential components in novel battery technology such as electrodes and electrolytes. They have excellent properties including light weight, appreciable mechanical strength, excellent plasticity, flexible processing, and easy fabrication in solid-state battery technology. The main advantages of solid polymer electrolytes are their chemical and physical stability, comparable performance to that of thin films (approx. 1 micrometer), and majority conduction of ions rather than electrons. However, the main drawback of solid electrolytes is interface stress due to electrode charging and discharging. Polymer electrolytes are used for batteries due to their ease of forming thin films with a large internal area; reduced resistance, which increases current density; stable and compatible contact with electrodes; and stability under ambient conditions such as temperature, pressure, and atmosphere to facilitate production on a mass scale.

Among polymer electrolytes, gel polymer electrolytes (GPEs) are a very important class of materials and have been used in electrochemical batteries such as fuel cells and electronic display devices [1, 2, 3, 4]. Compared to liquid and solid polymer electrolytes, GPEs are found to be very advantageous. In general, in these types of GPEs, salt provides ions for conduction and solvents provide a medium for this conduction. Plasticizers also help to decrease the glass transition temperature. Sodium may be considered an alternative to lithium as a negative electrode due to its low cost and natural abundance. The softness of this metal enables better electrical property contact with other components in the battery. The addition of nanofillers such as aluminum oxide (Al₂O₃) to this type of salt-based film rapidly enhances the electrical properties. The present work reports on a polymer electrolyte (PAN+NaF + Al₂O₃) and is concerned with solid-state electrochemical cells that are based on (PAN+NaF) electrolyte films. Several experimental techniques, such as structural, optical, electrical, tensile strength, differential scanning calorimetry (DSC), and DC conductivity measurements, were performed to characterize these polymer electrolytes. Based on these electrolytes, electrochemical cells were fabricated with anode/polymer electrolyte/cathode configurations. The discharge characteristics of the cell were studied for a load of 100 kΩ.

2. Experimental

2.1 Preparation of plasticized nanocomposite polymer electrolytes

Figure 1 illustrates the preparation method of solid polymer electrolytes. Table 1 shows various compositions of filler incorporated GPEs. Polyacrylonitrile (PAN) with a molecular weight of 1,50,000 g/mol was used as the host polymer and sodium fluoride (NaF) was used as the dopant salt. Ethylene carbonate (EC) was used as a plasticizer in the electrolyte and aluminum oxide (Al₂O₃) was used as a nanofiller. Solid polymer electrolytes were prepared by mixing PAN and NaF salt in dimethyl formamide (DMF). The solution thus obtained was.

Figure 1.

Preparation method of solid polymer electrolyte films.

Sample code		Composition (mol %)
	PAN	NaF	DMF + EC	Al2O3
PURE	700 mg	300 mg	20 ml + 880 mg	0
70PAN:30NaF:1 wt%	700 mg	300 mg	20 ml + 880 mg	1
70PAN:30NaF:2 wt%	700 mg	300 mg	20 ml + 880 mg	2
70PAN:30NaF:3 wt%	700 mg	300 mg	20 ml + 880 mg	3
70PAN:30NaF:4 wt%	700 mg	300 mg	20 ml + 880 mg	4

Table 1.

Various compositions of filler incorporated gel polymer electrolytes [5].

stirred in a magnetic stirrer for approximately 4 hours until we obtained a homogeneous translucent gel after the ethylene carbonate (EC) plasticizer was added to this solution and stirred for approximately 2 hours. After that, the Al2O3 nanofiller was added to this solution and stirred for 48 hours to disperse the nanofiller homogenously in the polymer matrix [2]. The resulting homogeneous mixture was then cast onto polypropylene dishes and the solvent was allowed to evaporate at room temperature. After the solvent had completely evaporated, the films were peeled off from the polypropylene dishes and pressed under a membrane hot press at a temperature of 40°C. The pressure applied by this method was 3.5 torr/cm², and we obtained flexible and self-standing polymer electrolytes. The samples consisted of 1 wt% Al₂O₃ (A1), 2 wt% Al₂O₃ (A2), 3 wt % Al₂O₃ (A3), and 4 wt% Al₂O₃ (A4). The prepared electrolyte membrane systems had a thickness of approximately 128 μm.

2.2 Materials characterization

Figure 2 shows a flowchart for the characterization of solid polymer electrolytes. In the present work, the prepared films were characterized by energy dispersive x-ray spectrometry (EDS) to determine the chemical composition in wt%. The UV–Vis spectrum was recorded by a Hewlett-Packard HP8452A diode array spectrometer. The mechanical properties of the prepared polymer electrolytes were determined using a Universal Tensile Machine (Instron Model 5565, Canada) with a constant crosshead speed of 10 mm/min. The sample dimensions were 25 mm × 40 mm × 0.1 mm. Additionally, DSC thermograms were recorded to measure the glass transition temperature and melting temperature of PAN-based electrolytes by using a Mettler instrument. The samples were heated sequentially from 50–360°C. Finally, transport characteristics and discharge characteristics, such as transference number, open circuit voltage (OCV), short circuit current (SCC), and power density, were determined. at a constant load of 100KΩ. Figure 3 illustrates a GPE film based on a Al₂O₃ nanofiller.

Figure 2.

Flow chart techniques for the characterization of solid polymer electrolytes.

Figure 3.

Gel polymer electrolyte film based on nanofillers (Al₂O₃).

3. Results and discussion

Figure 4 reveals the energy dispersive spectra of the prepared samples. From these spectra, the chemical composition of composite materials can be explained. The analysis indicates the presence of carbon (C), nitrogen (N), sodium (Na), fluoride (F), oxygen (O), and aluminum (Al) with chemical elements in the GPE of PAN + NaF (70:30) + Wt% Al₂O₃. EDS can be used to estimate the relative abundance and accuracy of quantitative analysis. This analysis explains the structural properties of prepared samples, and these properties may affect various factors [6, 7, 8]. With increasing nanofillers in the polymer composite, the atomic nature of the samples can be modified, and the results are represented in the above tabular forms.

Figure 4.

[a-d]. EDS spectra of PAN:NaF (70:30) + (1–4)Wt% Al₂O₃ nanocomposite gel polymer electrolyte films.

4. UV: Visible spectroscopy

Figure 5 shows the UV–Vis spectra of PAN with different wt. % ratios of NaF salt and Al₂O₃ nanoparticles at room temperature. The UV–Vis spectrum was recorded by a Hewlett-Packard HP8452A diode array spectrometer. The structural effect of salt and nanoparticles on the conductivity was also confirmed by UV–Vis spectroscopy. Optical absorption, particularly studying the shape and shift of the absorption edge, is a useful technique for understanding the basic mechanism of optically induced transitions in crystalline and noncrystalline materials. UV–Vis spectroscopy is used to identify inorganic complexation of molecules and their qualitative and quantitative measurements [9]. It is also used to identify the energy band gap values of the materials in the transmitting radiation. At an energy level, a photon is absorbed in its orbit. When an electron jumps from a lower energy level to a higher energy level. Transitions take place in a band gap energy as it rises in the absorption process called the absorption edge, where the optical band gap energies are determined [10, 11, 12]. The absorption rate is slightly changed by increasing the salt ratio of solvents and nanoparticles. The optical band gap of the polymer electrolytes was determined using UV–Vis spectra. It can be determined by

Figure 5.

(a-e): UV–VIS spectroscopic images of PAN:NaF (70:30) and different ratios of nanoparticle gel polymer electrolyte films at room temperature.

$$\mathrm{E}=\mathrm{h}\mathrm{c}/\lambda$$E1

where h is Planck’s constant (6.626 x 10⁻³⁴ joules sec), c is the light velocity (3 x 10⁸ meters/sec), and λ is the cutoff wavelength. Table 2 gives the wavelength values from the UV–Visible spectra. It is cleared that the optical energy band.

4.1 DSC characteristics

The Mettler instrument was calibrated with indium and zinc standards and the analyses were conducted under a nitrogen flow rate of ca. 20 mL/min. The sample was heated sequentially from 50–360°C. The change in transition temperature caused by the incorporation of nanofiller Al₂O₃ and plasticizer into the PAN+NaF complex was studied by DSC analysis. Figure 6 shows the DSC thermograms of 70PAN:30NaF and 1–4 wt% Al₂O₃.

Figure 6.

DSC thermographs of the 70PAN:30NaF, A1, A2, A3, and A4 samples.

Table 3 summarizes melting temperature (Tm) and the corresponding heat enthalpy (ΔHm) and the percentage of crystallinity (χ_c) of the prepared polymer electrolytes. The percentage of crystallinity was calculated by

Polymer electrolyte	Planck’s constant (h)	Light velocity (C)	Wavelength (Ǻ)	Optical energy band gap in (ev)
Pure PAN	6.626 x 10^−34 joules sec	3 x 10^8 meter/sec	350.12	3.54842
70PAN:30NaF:1 wt%	6.626 x 10^−34 joules sec	3 x 10^8 meter/sec	340.0	3.65404
70PAN:30NaF:2 wt%	6.626 x 10^−34 joules sec	3 x 10^8 meter/sec	352.0	3.52787
70PAN:30NaF:3 wt%	6.626 x 10^−34 joules sec	3 x 10^8 meter/sec	360.0	3.44803
70PAN:30NaF:4 wt%	6.626 x 10^−34 joules sec	3 x 10^8 meter/sec	350.0	3.54947

Table 2.

Optical energy band gap for PAN-based polymer electrolytes.

Sample	Tm(°C)	∆Hm^*((j/g)	Crystallinity (%)
Pure (Filler free)	317.22	398.6	98
70PAN:30NaF:1 wt%	309.43	298.3	87
70PAN:30NaF:2 wt%	304.02	243.6	74
70PAN:30NaF:3 wt%	283.42	132.5	60
70PAN:30NaF:4 wt%	295.57	175.4	63

Table 3.

T_m, ∆H_m^*, χ_c of 70PAN:30NaF, A1, A2, A3, A4 samples.

$${\mathrm{\chi }}_{\mathrm{c}}=\Delta {\mathrm{H}}_{\mathrm{m}}*/398.6\mathrm{j}{\mathrm{g}}^{-1}$$E2

where ΔHm* is the heat enthalpy of the polymer electrolytes, PAN has T_m,T_g and ΔH_m of 317°C, 107°C, and 398.6 Jg⁻¹respectively. From the table, it can be concluded that the incorporation of NaF salt and Al₂O₃ nanopowder into the polymer blend matrix decreases the T_m value, and the minimum Tm value is 283.42°C for the 3 wt.% Al₂O₃ nanopowder content. This observation suggests an increase in the crystallinity of the complexes because of the presence of excess nanopowder. It is also evident from conductivity studies that the conductivity of the complexes increases with increasing salt concentration and decreases for greater concentrations of nanopowder due to the formation of ion clusters. When sodium fluoride salt was added to the host polymer PAN, the results obtained indicated that the filler–polymer interaction influenced the speed of sodium ions in the polymer chain. This is in good agreement with TGA results [5, 13, 14, 15, 16].

4.2 Tensile test: 70PAN-30NaF-(1–4 wt%) Al₂O₃ composite

To effect the practical use of a polymer electrolyte, the electrolyte must remain structurally stable during manufacturing, cell assembly, storage, and usage, prevent flow from occurring within the cell to prevent self-discharge, and be easy to prepare in a repeatable manner. That is, mechanical strength is also an important factor when manufacturing polymer electrolytes. As noted earlier, incorporating additives such as ceramic powder can strengthen the dimensional stability of electrolyte membranes [17, 18, 19, 20].

The addition of nanoparticles increased both the modulus and the strength of the polymer nanocomposites. Additionally, the toughness (area under the stress–strain curve before rupture) increased significantly. Figure 7 shows the tensile strength (the maximum stress in the stress–strain curve, MPa) and Young’s modulus (the slope of the stress–strain curve in the low strain region) as a function of nanoparticle volume content. Both the tensile strength and Young’s modulus increased with increasing functionalized particle loading. Compared to the pure polymer, the strength and Young’s modulus of the 4 wt% filled nanocomposite sample increased by approximately 99%. The imagination of the nanoparticles was observed to have a greater effect on the Young’s modulus. Moreover, the relatively uniform distribution of Al₂O₃ particles and decrease in interparticle distance with increasing particle loading in the matrix results in polymer nanocomposites having increased resistance to indentation. For a given volume fraction, nanoparticles are much closer to each other than microparticles in the matrix, and hence nanoparticles will more strongly resist the penetration of the indentation in the matrix [21]. This results in higher microhardness for nanocomposites than that of polymers at a constant volume fraction of particles.

Figure 7.

Tensile test of 70PAN-30NaF-(1–4 wt%)Al₂O₃Composite.

4.3 DC conductivity studies

4.3.1 Conductance spectra for PAN:NaF gel polymer electrolytes

Figure 8 shows the ionic conductivity in addition to NaF salt with the host polymer PAN. The conductivity increased with the enhancement of NaF salt from 10 to 30 wt%. For 40 wt% NaF salt, the ionic conductivity was decreased. Table 4 gives the ionic conductivity values. With the doping of NaF salt, the number of free ions also increased in the host polymer, resulting in enhanced conductivity. At higher concentrations, the enhanced viscosity of the polymer reduced the ionic conductivity. For 30 wt%, NaF shows a higher conductivity of 1.82 x 10⁻⁴ S cm⁻¹ due to its less crystalline nature compared to other compositions [16, 17, 18].

Figure 8.

Composition dependence of conductivity in the PAN+NaF system.

GPEs	Ionic Conductivity at 303 K	373 K	Activation energy(eV)	Transference Number
				tion	tele
PAN: NaF (90:10)	5.46 x 10^−6	2.85 x 10^−5	0.47	0.965	0.04
PAN:NaF (80:20)	1.62 x 10^−5	2.42 x 10^−5	0.32	0.972	0.014
PAN:NaF (70:30)	1.82 x 10^−4	2.96 x 10^−3	0.25	0.989	0.03
PAN:NaF (60:40)	2.64 x 10^−5	1.32 x 10^−5	0.28	0.969	0.02

Table 4.

DC conductivity, E_a, ionic transference numbers of various compositions of PAN:NaF gel polymer electrolytes.

Conductivity studies were carried out for all the prepared polymer electrolytes to understand the conduction mechanism. Figure 9 shows the ionic conductivity versus nanofiller (Al₂O₃) concentration of the polymer electrolyte PAN+NaF complexed system with varying weight percentages of nanofiller in the temperature range 303 K to 373 K. Table 4 presents the conductivity data at room temperature and at 373 K. We conclude that the conductivity increases as the nanofiller content increases up to 4 wt% due to the high.

Figure 9.

Ion conductivity (σ) of polymer electrolyte films as a function of wt% of Al₂O₃ concentration.

Amorphous nature of the polymer electrolyte, which provides more free mobile protons (carriers), thus giving rise to higher conductivity [22].

The enhancement in conductivity is not only due to the increment of mobile charge carriers but also due to ethylene carbonate (EC), which allows greater dissolution of the electrolyte salt and nanofiller, resulting in an increased number of charge carriers and hence an increase in conductivity. The maximum value of conductivity obtained at room temperature is 4.82 × 10–3 S cm⁻¹. This conductivity value is 10 orders greater than that of pure PAN (10⁻¹⁴ S cm⁻¹), as reported by Pan and Zou [23]. The conductivity increases with the incorporation of nanofiller wt %, which might be due to ion pair or aggregate formation [24]. The polymer electrolytes lead to an increase in the viscosity of the polymer electrolyte film due to the incorporation of a large amount of salt and nanofiller content, which reduces proton transportation and impedes the mobility of charge carriers, resulting in a decrease in proton conductivity.

Figure 10 Illustrates the variation of ionic conductivity with temperature for different wt% of Al₂O₃. The ionic conductivity was calculated using the formula given in Eq. 3.

Figure 10.

Log σ versus 1000/T of PAN+NaF complexed films for different wt% of Al₂O₃.

$$\mathrm{\sigma }=\mathsf{t}/{\mathsf{A}\mathsf{R}}_{\mathsf{b}}$$E3

where t and A represent the thickness and the area of the electrolyte specimen, respectively [25]. R_b is the bulk resistance of the electrolyte obtained from the complex impedance measurement. The ionic conductivity depends on the overall mobility of ion species present in the electrolyte and the polymer, which is determined by the free volume made by filler and plasticizer around the polymer chain. In the present study, conductivity enhancement was observed when the Al₂O₃ filler and EC plasticizer were incorporated into the polymer salt system. The polymer electrolytes considered in the present study exhibited an Arrhenius type of conduction [26]. The polymer electrolyte containing 3 wt% nanofiller showed an ionic conductivity of 5.96 × 10⁻³ Scm⁻¹.

4.3.2 Transference number measurements

To measure the conductivity of prepared polymer electrolytes, the transfer numbers play a vital role. To determine transfer numbers, Wagner’s polarization method can be used. The prepared PAN:NaF sample was placed between two silver electrodes. After the circuit was closed, DC voltage was applied to the sample to measure the polarization current. Figure 11 shows the final stabilized current values. The polarization current was decreased with respect to increasing time due to predominantly ions [19]. Table 4 shows the transfer numbers for 10 to 40 wt% NaF doped with PAN as 0.965, 0.972, 0.989, and 0.969.

Figure 11.

Polarization current vs. time plot for the PAN:NaF polymer composite at 303 K.

5. Working principle and design of ideal solid polymer batteries

An ideal polymer battery exhibiting a polymer electrolyte membrane, a positive electrode and a negative electrode. The positive electrode is flexible with elastic materials and the negative electrode consists of metal foil. During the recharging process, the direction of flow of electrons takes place in the opposite (anode-to-cathode) direction. Designing new solid-state batteries that have better performance over the life cycle also depends on the outstanding operation of electrode–electrolyte interfaces, as shown in Figure 12.

Figure 12.

Schematic diagram of a solid polymer battery.

Most polymeric materials are insulators that do not conduct electricity in the medium through ions or electrons. Some of the polymers are “immobile solvents” at which the salt and the polymer are completely mixed and act as a polymer electrolyte [27, 28, 29, 30, 31]. Compared to solid electrolytes, polymer electrolytes have both cations and anions in the mobile state. Due to this, polymer batteries designed to be rechargeable face several challenges. Fabrication of polymer batteries is an important method to pass ions from the anode to the cathode. Here, sodium metal was considered an anode and carbon mixed with iodine was taken as a cathode material.

For some PEO N:LiCF₃SO_3, mobilization takes place at the anode due to anions, and it reacts with Li + cations, which form a thin layer of lithium salt and act as a conducting medium.

$$\mathrm{L}{\mathrm{i}}^{+}+{\mathrm{X}}^{–}\mathrm{L}\mathrm{i}\mathrm{X}$$

The results show that the battery resistance is increased, and Li + ions decrease the capacity. Polarization takes place in an electrolyte due to the mobility of ions in the battery system with respect to negative ions.

5.1 Discharge characteristics of a solid-state battery

Solid-state batteries provide well-contained energy conversion devices, which greatly contribute to the needs of humankind. Zero-emission vehicles of the future will be battery powered only. Many nonpolluting energy conversion devices, such as photovoltaic systems, require the concomitant use of rechargeable batteries for energy storage. Batteries may be considered storehouses for electrical energy [1, 2, 3, 4, 6, 7, 8, 9, 10]. The size of a battery ranges from a tiny coin to that of a large house. Tiny coin and button-sized cells are used for electronic applications requiring only small capacity. Liter-container sized batteries are commonly used in motor vehicles for starting, lighting, and ignition purposes. The basis for battery technology is that the chemical energy derived from the chemical reactions in the battery is transformed into electrical energy. Figure 13 shows the fabrication and operation of a solid-state battery.

Figure 13.

Fabrication and operation of a solid-state battery.

6. [70PAN + 30NaF] gel polymer electrolyte system

6.1 Discharge characteristics

A proton battery using the membrane with the maximum ionic conductivity was constructed with sodium (Na) as an anode material and a mixture of iodine (I₂), carbon, and a piece of GPE taken as the cathode electrode between the 70PAN:30NaF electrolyte film [5]. Figure 10 represents the discharge characteristics of the electrochemical cell with an applied load of 100 k Ω at room temperature. From these results, the OCV of the cell was observed for 118 hours and plotted against time, as shown in Figure 14. A stabilized voltage of 2.78 V was obtained from the cell. The discharging curve initially decreases with the voltage of the cell, which may be due to the polarization effect. Table 5 lists the OCV and discharge time for the cell [32, 33, 34, 35, 36, 37].

Figure 14.

Discharged curve of the solid-state cell configuration of Na/PAN:NaF (70:30)/cathode (I₂+ C + electrolyte+Al₂O₃) at a load of 100 kῼ.

Cell parameters	70PAN:30NaF
Area of the electrolyte (cm^2)	1.30
Cell weight (gm)	1.5
OCV (V)	2.78
SCC (μA)	1.2
Discharge time for plateau region (h)	118
Density of power (mW/kgg)	2.94
Density of energy (mWh/kg)	265.4
Density of current (mW/kg)	2.32
Capacity of discharge (μA h^−1)	152.4

Table 5.

Cell parameters of PAN:NaF (70:30) gel polymer electrolytes.

A solid-state electrochemical cell was fabricated with an anode Na/PAN:NaF (70:30)/cathode (I₂ + C + electrolyte+Al₂O₃). The thickness of both the electrodes is 1 mm. The surface area and thickness of the PAN+NaF + Al₂O₃ GPE were 1.28 cm2 and 128 μm, respectively. The discharge characteristics of the cell for a constant load of 100 kΩ were evaluated at room temperature as shown in Figure 14.

The initial sharp decrease in the voltage in these cells may be due to polarization and the formation of a layer of sodium salt at the electrode–electrolyte interface [38, 39, 40, 41]. Cell parameters such as OCV, SCC, current density, power density, energy density, and discharge capacity have been evaluated in the highest conducting GPE system PAN:NaF (70:30) + nanofiller (Al₂O₃) in this electrochemical cell. Table 6 shows the obtained data. The current density is calculated using the SCC value and area of the cell. The power density value is obtained by taking the OCV and weight of the cell into consideration. The energy density value is calculated by evaluating the time taken for the plateau region [5]. From Table 6, it is obvious that the cell with the composition PAN:NaF (70:30) + nanofiller Al₂O₃ exhibits better performance [26]. It is confirmed that gel-state cell parameters are better than the earlier reported sodium-based polymer electrolyte cell system (Figure 15) [27, 28, 29, 30, 31].

Cell parameters	70PAN:30NaF:3 wt% Al2O3
Area of the electrolyte (cm^2)	1.20
Cell weight (g)	1.64
OCV (V)	3.20
SCC (mA)	1.6
Discharged time for plateau region (h)	142
Density of power (W/kgg)	2.94
Density of energy (Wh/kg)	324.7
Density of current (Mw/kg)	2.35
Capacity of discharge (μA h^−1)	168.2

Table 6.

Cell parameters of the PAN:NaF + Al₂O₃/(I₂+ C + electrolyte) polymer electrolyte battery.

Figure 15.

Discharge characteristics of PAN:NaF complexed with 3 wt% Al₂O₃ nanofiller polymer electrolyte electrochemical cell (load =100 kΩ).

7. Conclusions

Proton-conducting GPEs consisting of NaF salt dissolved in a plasticizing solvent of EC and DMF, immobilized in a host polymer 70PAN + 30NaF + (1–4 wt%) Al₂O₃ (nanofiller) were synthesized and characterized. The complexation of the salt and nanofiller with the polymer was confirmed by ED. UV–Vis light absorption reveals that the chemical structure of the polymer is identical to that of the polymer formed electrochemically. The various absorption rates given for different wavelengths and optical energy band gaps were determined. The tensile test of the prepared samples was verified by a stress–strain graph. The tensile strength was increased to 5.9 MPa for the polymer electrolyte with 3 wt% nanocomposite compared to the filler-free electrolyte. A decrease in the degree of crystallinity and an increase in the amorphous nature were observed, while an increase in conductivity was observed with increasing nanofiller concentration and temperature. The heat flow observed by DSC technique that the transference data indicates the conduction in the polymer electrolyte is predominantly due to ions rather than electrons. Using a PAN:NaF (70:30) GPE system, a solid–state battery (Na/PAN:NaF (70:30) + EC + DMF/(I₂ + C + electrolyte)) was fabricated, and its discharge characteristics were studied. These results were found to be comparable with existing results.

Acknowledgments

The author thanks Vice Chairman of Dayananda Sagar Institutions, Bangalore Dr. D. Premachandra Sagar; Vice-Chancellor Prof. KNB Murthy; and Dean Dr. A. Srinivas SOE, Dayananda Sagar University for constant support and encouragement. I especially thank my beloved student Narasimha Rao Maragani, who supported and helped me with the research work.