High-Performance Gel Electrolyte Asymmetric Supercapacitor Based on Polypyrrole–Tungsten Disulfide Nanocomposite

Abstract

In this work, a polypyrrole–tungsten disulfide (PPy–WS₂) nanocomposite was synthesized through oxidative polymerization and evaluated as an electrode material for supercapacitors. Structural and morphological analyses confirmed the successful integration of WS₂ within the PPy matrix. Electrochemical testing revealed a high specific capacitance of 816 F g⁻¹ at a scan rate of 1 mVs⁻¹, together with excellent cycling durability. To further assess device-level performance, an asymmetric supercapacitor was assembled using the PPy–WS₂ nanocomposite as the positive electrode, activated carbon as the negative electrode, and a PVA/KOH gel electrolyte. The device achieved an energy density of 41.6 Wh kg⁻¹ and a power density of 1500 W kg⁻¹, while maintaining 105% of its capacitance after 2500 charge–discharge cycles. The prototype was also able to power a light-emitting diode, highlighting its practical potential. These findings demonstrate that the synergistic coupling between polypyrrole and tungsten disulfide substantially improves electrochemical behaviour, positioning the PPy–WS₂ nanocomposite as a promising candidate for advanced energy storage applications.

1. Introduction

Rapid industrialization and increasing environmental concerns have intensified the demand for clean and renewable energy sources such as solar, wind, and geothermal energy [1,2,3]. However, the intermittent nature of these energy sources necessitates the development of efficient energy storage technologies to ensure a stable and reliable energy supply [4,5]. Currently, batteries, supercapacitors, and fuel cells are the most widely employed energy storage systems [6,7]. Among these, supercapacitors have attracted significant research interest owing to their fast charge–discharge capability, high power density, wide operating temperature range, and operational safety [8,9,10]. Despite these advantages, the relatively low energy density of supercapacitors limits their broader practical application [11]. Consequently, extensive efforts have been devoted to enhancing their electrochemical performance through material design and device engineering [12,13,14].

The electrochemical performance of a supercapacitor is strongly governed by the properties of its electrode and electrolyte materials [15,16,17,18]. To date, a wide range of electrode materials has been explored, including carbon-based materials, metal oxides, and conducting polymers [18,19]. Conducting polymers such as polypyrrole (PPy), polyaniline (PANI), and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) have garnered considerable attention as supercapacitor electrodes due to their high pseudocapacitance, good electrical conductivity, and low cost [20,21,22]. Among them, polypyrrole has been extensively investigated because of its facile synthesis, high theoretical capacitance, and reversible redox behaviour. Nevertheless, intrinsic limitations such as poor cycling stability and structural degradation during repeated charge–discharge processes hinder the practical application of polypyrrole, thereby motivating the development of composite electrode materials to address these challenges [23,24]. In this context, various conductive and electrochemically active materials have been integrated with conducting polymers to enhance their electrochemical performance. Recently, two-dimensional (2D) materials, including transition metal dichalcogenides, MXenes, and graphene-based materials, have emerged as promising composite components owing to their unique physicochemical properties [12,19]. These materials offer high electrical conductivity, large specific surface area, abundant active sites, and favourable ion transport pathways, which collectively contribute to improved charge-storage capability, rate performance, and cycling stability of supercapacitor electrodes. Chikkatti et al. [25] reported the synthesis of a PPy–MXene nanocomposite for supercapacitor applications, where the fabricated electrode delivered a specific capacitance of 987.5 F g⁻¹ at 1.25 A g⁻¹, where cycling stability, retaining 91% of its initial capacitance after 5000 cycles. Similarly, Wu et al. [26] developed a CoNi layered double hydroxide/polypyrrole nanotube (CoNi LDH/PPyNT) composite electrode, which exhibited a high specific capacitance of 1660.14 F g⁻¹ at 1 A g⁻¹. Furthermore, the asymmetric supercapacitor device assembled using this electrode achieved an energy density of 86.23 Wh kg⁻¹ and a power density of 973.65 W kg⁻¹.

Tungsten-based materials have recently gained considerable attention due to their promising properties for energy-storage applications. Tsyganov et al. [27] reported the synthesis of W_1.33CTz i-MXene via a hydrothermal route, followed by the fabrication of Ti₃C₂T_x/W_1.33CTz (20 wt%) composite electrodes. When tested in H₂SO₄, LiCl, and KOH electrolytes, the electrodes delivered specific capacitances of 375, 171, and 235 F g⁻¹, respectively, at a scan rate of 5 mV s⁻¹. Among tungsten-based materials, transition metal dichalcogenides have gained considerable attention as composite components for supercapacitor electrodes owing to their unique layered structure, large specific surface area, rich redox-active sites, and favourable electrochemical activity [28,29]. When combined with conducting polymers, these materials can effectively improve electrical conductivity, facilitate ion diffusion, and enhance structural stability during repeated charge–discharge processes. In this context, Lian et al. [30] reported the synthesis of a PPy/MoS₂ composite via a hydrothermal method, and the resulting electrode delivered a maximum specific capacitance of 895.6 F g⁻¹ at 1 A g⁻¹, retaining 98% of its initial capacitance after 10,000 cycles. Adhikari et al. [31] reported a WS₂–PPy-based self-powered supercapacitor, where the fabricated electrode delivered a specific capacitance of 245 F g⁻¹ at 1 A g⁻¹. Similarly, Gupta et al. [32] developed a PEDOT:PSS/WS₂ composite electrode for supercapacitors, which exhibited a specific capacitance of 118 mF cm⁻² at 0.5 mA cm⁻².

In this work, a polypyrrole–tungsten disulfide nanocomposite was prepared through oxidative polymerization for supercapacitor use. The physicochemical characteristics of the obtained material were systematically analyzed using multiple characterization methods. Electrochemical behaviour was assessed by cyclic voltammetry, galvanostatic charge–discharge, and impedance spectroscopy. In addition, the PPy–WS₂ nanocomposite served as the electrode material in constructing a gel electrolyte-based asymmetric supercapacitor, and its performance was comprehensively evaluated. The practical utility of the assembled device was demonstrated by powering a light-emitting diode.

2. Materials and Methods

In the present study, all chemicals were procured from Sigma-Aldrich, Pune, India and used without further purification. For the synthesis of polypyrrole, pyrrole (C₄H₄NH, 98% purity) was employed as the monomer, while FeCl₃·6H₂O served as the oxidizing agent for polymerization.

2.1. Synthesis of PPy–WS₂ Nanocomposite

The WS₂ used in this study was synthesized via hydrothermal method using a previously reported study [33]. The PPy–WS₂ nanocomposite was synthesized via an oxidative polymerization method. Initially, 0.62 g WS₂ was dispersed in 20 mL of deionized (DI) water under ultrasonication to obtain a homogeneous suspension. Subsequently, a 0.1 M aqueous pyrrole solution was prepared, and 10 mL of this solution (1.0 mmol pyrrole) was added dropwise to the WS₂ dispersion. The mixture was further ultrasonicated for 30 min to ensure uniform adsorption and interaction of pyrrole monomers on the WS₂ surface. Thereafter, 4 g of FeCl₃·6H₂O (14.8 mmol) was dissolved in 50 mL of DI water (≈0.30 M solution) and slowly introduced into the reaction mixture under continuous magnetic stirring to initiate oxidative polymerization of pyrrole. The reaction was allowed to proceed under constant stirring until complete polymer formation. The resulting precipitate was collected and thoroughly washed with ethanol three to four times to remove unreacted species and residual oxidant. Finally, the obtained product was dried at 70 °C overnight in an incubator. Schematic representation shown in Figure 1.

2.2. Characterization

The synthesized nanocomposite was subjected to a series of analytical techniques to confirm its physicochemical characteristics. Crystallographic information was obtained using X-ray diffraction (XRD) on a Bruker D-8 diffractometer equipped with Cu Kα radiation (λ = 1.5406 Å). The presence of functional groups was verified through, Fourier transform infrared spectroscopy (FTIR, Perkin Elmer, Pune, India) across the spectral window of 4000–400 cm⁻¹. Surface morphology and microstructural features were examined through field-emission scanning electron microscopy (FESEM) at varying magnifications, providing detailed insights into particle distribution and film texture.

Electrochemical testing was carried out using a Gamry electrochemical workstation, Santiago, Chile. The measurements were performed in a standard three-electrode setup, with the prepared material serving as the working electrode, a platinum wire acting as the counter electrode, and a Hg/HgO electrode used as the reference. All experiments were conducted in an aqueous electrolyte of 2 M KOH to evaluate the electrochemical behaviour of the synthesized nanocomposite.

2.3. Electrode Preparation

For evaluation of single-electrode performance, the working electrode was prepared using the synthesized PPy–WS₂ nanocomposite as the active material. Carbon black was incorporated as a conductive additive, while polyvinylidene fluoride (PVDF) acted as the binder, maintaining a weight ratio of 85:10:5. The 5 mg components were dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a uniform slurry, which was continuously stirred for four hours to ensure homogeneity. This slurry was then applied onto pre-cleaned nickel foam substrates (1 × 2 cm) and dried in an incubator at 70 °C for 1 h. The resulting PPy–WS₂-coated nickel foam electrode was subsequently employed as the working electrode for electrochemical characterization.

The cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) curves were used to determine various supercapacitive parameters [34]. The specific capacitance (C_sp) values of prepared electrodes from CV curves were calculated using Equation (1):

$$C_{sp}={\displaystyle \frac{\int I\left(V\right) dV}{m \times \upsilon \times ∆V}}$$

(1)

where $\int I\left(V\right) dV$ is the area under the CV curve, $\mathrm{m}$ is the mass of the active material (g), $\upsilon$ is the potential scan rate (V s⁻¹), and $∆\mathrm{V}$ is the voltage window used during CV measurement (V).

The value of the specific capacitance (C_sp) via GCD curves was calculated using Equation (2):

$$C_{sp}={\displaystyle \frac{\int I\left(t\right)dt}{m \times ∆V}}$$

(2)

where $\int I\left(t\right)dt$ is the total area under the discharge curve, $\mathrm{m}$ is the mass of the active materials (g), and $∆\mathrm{V}$ is the potential window used during charging or discharging (V).

2.4. Gel Electrolyte-Based Supercapacitor Device Fabrication

The asymmetric gel electrolyte-based supercapacitor device was fabricated using PPy–WS₂/Ni as the positive electrode and activated carbon/Ni (AC/Ni) as the negative electrode. A PVA/KOH gel served as the electrolyte. The gel was prepared by dissolving 1 g of polyvinyl alcohol (PVA) and 1 g of potassium hydroxide (KOH) in deionized water under continuous magnetic stirring at 80 °C until a transparent gel was obtained [10,22]. The prepared gel was then applied to both electrodes and allowed to dry. A sheet of butter paper was used as the separator, and the electrodes were assembled by placing the separator between them. The assembled device was sealed with Teflon tape to ensure mechanical stability, while small copper strips were attached to each electrode to serve as current collectors and connection points.

The performance of the fabricated device was measured using the following equations [35]:

$$C_p= {\displaystyle \frac{\int Idt}{mv}}$$

(3)

$$E={\displaystyle \frac{C{V}^2}{2\times 3.6}}$$

(4)

$$P={\displaystyle \frac{E\times 3600}{∆t}}$$

(5)

3. Results and Discussion

The structural properties of the synthesized PPy–WS₂ nanocomposite were investigated using X-ray diffractometer. The XRD pattern, shown in Figure 2a, exhibits distinct diffraction peaks at 2θ values of 14.3°, 27.4°, 32.5°, 33.5°, 39.4°, 49.6°, 58.0°, and 60.3°, which can be indexed to the (002), (004), (100), (101), (103), (105), (110), and (112) crystallographic planes of hexagonal WS₂, respectively. These peaks are in good agreement with the standard JCPDS card No. 84-1398 [34], confirming the crystalline nature of WS₂ within the composite. In addition, a broad diffraction peak observed at around 25.3° reflection of amorphous polypyrrole, indicating the presence of PPy with low crystallinity. The coexistence of characteristic peaks of WS₂ along with the broad PPy peak confirms the successful formation of the PPy–WS₂ nanocomposite.

The functional groups present in the synthesized PPy–WS₂ nanocomposite were characterized using FTIR spectroscopy. Figure 2b illustrates the FTIR peaks obtained for the composite. The spectrum reveals several distinct absorption bands, confirming the coexistence of polypyrrole and WS₂. Peaks at 1009 cm⁻¹ and 1051 cm⁻¹ correspond to in-plane C–H deformation and C–N stretching vibrations of the pyrrole ring, indicating the formation of the PPy backbone. The absorption band at 1220 cm⁻¹ is attributed to C–N stretching of the polaron structure, typically associated with the doped state of PPy. A peak at 1393 cm⁻¹ reflects C–N stretching and ring deformation modes, while the band at 1454 cm⁻¹ is linked to C=C stretching vibrations of the pyrrole ring. The strong absorption at 1571 cm⁻¹ arises from C=C/C–C stretching of the conjugated PPy backbone, confirming the π-conjugated nature of the polymer. Additionally, the band at 2972 cm⁻¹ corresponds to C–H stretching vibrations, and the broad absorption at 3678 cm⁻¹ is assigned to O–H stretching vibrations, likely due to adsorbed moisture or surface hydroxyl groups. Together with WS₂-related vibrations observed at lower wavenumbers, these features validate the successful formation of the PPy–WS₂ nanocomposite and highlight the interfacial interactions between the polymer chains and WS₂ nanosheets.

The textural characteristics of the PPy–WS₂ nanocomposite were examined through nitrogen adsorption–desorption analysis. As depicted in Figure 2c, the isotherm displays a type IV profile, accompanied by a pronounced hysteresis loop, signifying the presence of mesoporous structures. The BET method yielded a specific surface area of 23 m² g⁻¹. Furthermore, BJH pore size distribution analysis revealed an average pore radius of approximately 2.8 nm, corroborating the mesoporous nature of the composite. The emergence of mesopores is attributed to the uniform deposition of PPy on WS₂ nanosheets, which effectively inhibits restacking and generates accessible pore channels. This mesoporous framework is particularly beneficial for electrochemical applications, as it promotes efficient electrolyte diffusion and enhances ion transport during charge–discharge cycles [10].

The morphological features of the synthesized PPy–WS₂ nanocomposite were investigated using FESEM, and the corresponding micrographs are shown in Figure 2d–f. The FESEM images reveal spherical PPy particles uniformly distributed across the nanosheet-like WS₂ framework, confirming the successful integration of PPy onto the WS₂ surface. In addition, the composite displays large, interconnected pores formed through the hierarchical assembly of PPy spheres on WS₂ nanosheets. These porous structures are consistent with the mesoporous characteristics identified in BET analysis and are anticipated to improve electrolyte accessibility and facilitate ion transport, thereby enhancing the electrochemical performance of the material in energy storage applications. The elemental composition of the synthesized PPy–WS₂ nanocomposite was analyzed using energy-dispersive X-ray spectroscopy (EDS), and the corresponding spectrum is presented in Figure 2g. The EDS results confirm the presence of carbon (C), nitrogen (N), and oxygen (O), which are characteristic of the polypyrrole (PPy) matrix. Additionally, distinct peaks corresponding to tungsten (W) and sulfur (S) are observed, verifying the incorporation of tungsten disulfide (WS₂) into the composite. The simultaneous detection of these elements demonstrates the successful formation of the PPy–WS₂ hybrid material. Importantly, no extraneous impurity peaks were detected within the sensitivity limits of the technique, indicating the high purity of the synthesized nanocomposite.

The electrochemical properties of the synthesized PPy–WS₂ nanocomposite were assessed using a three-electrode system in 2 M KOH electrolyte. The cyclic voltammetry (CV) curves obtained at different scan rates are shown in Figure 3a. The CV profiles display distinct oxidation and reduction peaks, indicative of a pseudocapacitive charge-storage mechanism governed by reversible faradaic redox reactions of the PPy backbone and WS₂ surface. As the scan rate increases, the oxidation peaks shift toward higher potentials and the reduction peaks toward lower potentials, reflecting enhanced polarization and internal resistance at faster sweep rates. Importantly, the CV curves maintain their overall shape even at elevated scan rates, demonstrating excellent electrochemical reversibility and efficient charge-transfer kinetics. The PPy–WS₂ nanocomposite achieves a high specific capacitance of 816 F g⁻¹ at a scan rate of 1 mV s⁻¹. With increasing scan rate, the capacitance gradually decreases to 450, 366, 298, 255, 227, 206, and 150 F g⁻¹ at 5, 10, 20, 30, 40, 50, and 100 mV s⁻¹, respectively. This decline at higher scan rates is attributed to restricted ion diffusion and incomplete utilization of electroactive sites. Overall, the combination of high capacitance and favourable rate capability underscores the promise of the PPy–WS₂ nanocomposite as a high-performance electrode material for supercapacitor applications.

The electrochemical performance of the PPy–WS₂ nanocomposite was further evaluated using galvanostatic charge–discharge (GCD) measurements at different current densities, with the corresponding profiles presented in Figure 3b. The GCD curves exhibit quasi-symmetric, non-linear triangular shapes, characteristic of pseudocapacitive behaviour, which are consistent with the cyclic voltammetry results. The slight deviation from an ideal triangular profile reflects the contribution of faradaic redox reactions during the charge–discharge process. At a current density of 2 A g⁻¹, the PPy–WS₂ nanocomposite delivers a high specific capacitance of 460 F g⁻¹. As the current density increases, the capacitance gradually decreases to 354, 272, 240, 192, 163, 150, 129, 122, and 111 F g⁻¹ at 3, 4, 5, 6, 7, 8, 9, 10, and 11 A g⁻¹, respectively. This decline at higher current densities is attributed to restricted electrolyte ion diffusion and incomplete utilization of electroactive sites under rapid charge–discharge conditions. The combination of high capacitance values and favourable rate capability highlights the potential of the PPy–WS₂ nanocomposite as an efficient electrode material for advanced supercapacitor applications.

The superior electrochemical performance of the PPy–WS₂ nanocomposite arises from the synergistic interaction between polypyrrole and WS₂, coupled with the composite’s favourable structural and morphological attributes. The conductive PPy matrix provides abundant redox-active sites and facilitates efficient electron transport during charge–discharge processes, while the layered WS₂ nanosheets contribute a mechanically robust framework and additional surface-accessible electroactive sites. The intimate interfacial contact between PPy and WS₂ promotes rapid charge transfer and effectively suppresses the restacking of WS₂ layers. Moreover, the hierarchical porous architecture, confirmed by FESEM and BET analyses, generates interconnected mesoporous channels that enhance electrolyte penetration and reduce ion diffusion pathways. This structural advantage ensures effective utilization of electroactive sites, even under relatively high current densities. The combination of high electrical conductivity, reversible faradaic activity, and efficient ion transport collectively results in elevated specific capacitance and excellent rate capability. These synergistic effects underscore the potential of the PPy–WS₂ nanocomposite as a high-performance electrode material for energy storage applications.

Electrochemical impedance spectroscopy (EIS) was employed to probe the charge transport and interfacial characteristics of the PPy–WS₂ nanocomposite. Following the article Good Practice Guide for Papers on Supercapacitors and Related Hybrid Capacitors, the plotted Nyquist graph is shown in Figure 3c [35]. The impedance spectrum can be divided into three distinct regions. In the high-frequency region, the intercept of the curve with the real axis represents the solution resistance (R_s), which originates from the combined resistance of the electrolyte, electrode material, and current collector at the electrode–electrolyte interface [36]. In the mid-frequency region, a depressed semicircle is observed, the diameter of which corresponds to the charge-transfer resistance (Rct) associated with faradaic reactions occurring at the electrode surface. In the low-frequency region, the inclined straight line reflects Warburg impedance, indicative of ion diffusion processes within the electrode material. Equivalent circuit fitting of the Nyquist plot yields a solution resistance (R_s) of 0.8 Ω and a charge-transfer resistance (Rct) of 1.2 Ω for the PPy–WS₂ nanocomposite. These relatively low resistance values highlight efficient electron transport and rapid interfacial charge transfer, facilitated by the conductive PPy network and its synergistic interaction with WS₂ nanosheets. Importantly, the resistance values are markedly lower than those reported for pristine PPy electrodes, underscoring the beneficial role of WS₂ incorporation in minimizing interfacial resistance and enhancing the overall electrochemical performance of the composite.

Cycling stability is a critical parameter for assessing the long-term electrochemical reliability of electrode materials. For the PPy–WS₂ nanocomposite, cycling performance was evaluated over 5000 charge–discharge cycles shown in Figure 3d. The electrode demonstrates remarkable durability, retaining 98% of its initial specific capacitance after 5000 cycles, thereby confirming excellent electrochemical stability. The coulombic efficiency obtained 89% after 5000 cycles. In contrast, pristine PPy electrodes typically exhibit poor cycling performance due to volumetric swelling and structural degradation during repeated redox processes. Further rate capability investigations were performed at varying scan rates and current densities, as illustrated in Figure 3e,f. The results confirm that the synthesized composite exhibits outstanding rate capability.

The obtained electrochemical performance is superior to that of bare WS₂ and PPy, which can be attributed to the synergistic effect between the two components. Ratha et al. [34] reported that WS₂ synthesized via a hydrothermal method exhibited a specific capacitance of 70 F g⁻¹ at a scan rate of 2 mV s⁻¹. Similarly, Dubal et al. [37] demonstrated that polypyrrole delivered a specific capacitance of 586 F g⁻¹ at 2 mV s⁻¹. The incorporation of WS₂ nanosheets enhances the mechanical robustness of the composite by serving as a stable support framework, effectively suppressing polymer swelling and mitigating structural collapse during cycling. Furthermore, the strong interfacial interaction between PPy and WS₂ ensures sustained electrical connectivity and structural integrity throughout the prolonged operation. Consequently, the PPy–WS₂ nanocomposite exhibits significantly improved cycling stability, underscoring its promise as a practical electrode material for high-performance supercapacitor applications.

The charge-storage kinetics of the fabricated electrode were investigated using Dunn’s model to distinguish between surface-controlled (capacitive, non-faradaic) and diffusion-controlled (faradaic) charge contributions. The nature of the charge-storage mechanism was initially evaluated from cyclic voltammetry curves recorded at different scan rates. The current response (i) at a given potential (V) follows a power-law relationship with the scan rate (v), expressed as [38,39]:

$$i={av}^b$$

(6)

Applying log on both side to above equation can be converted into the following form:

$$\log \left(i\right)=\log \left(a\right)+b \mathrm{l}\mathrm{o}\mathrm{g}\left(v\right)$$

(7)

By plotting log(i) against log(v) shown in Figure 4a, the slope of the linear fit provides the b-value, which offers insight into the prevailing charge-storage mechanism. A b-value of 0.5 is indicative of diffusion-controlled, battery-type behaviour, whereas a value of 1.0 corresponds to a surface-controlled capacitive process. In this study, the PPy–WS₂ nanocomposite exhibited a b-value of 0.62, suggesting that the charge-storage mechanism is predominantly pseudocapacitive in nature, arising from a combined contribution of surface-controlled capacitive processes and diffusion-controlled faradaic reactions.

Further exact contribution can be measured by using following equation [40,41,42,43]:

$$i\left(V\right)= K_{1}v+ K_2\sqrt{v}$$

(8)

By plotting $\sqrt{v}$ vs. $i/\sqrt{v}$ (Figure 4b), the kinetic parameters K₁ and K₂ were extracted based on the Dunn’s model. These parameters were subsequently employed to quantitatively distinguish the surface-controlled (capacitive) and diffusion-controlled (faradaic) charge contributions at different scan rates, as summarized in Figure 4c. At a low scan rate of 1 mV s⁻¹, the PPy–WS₂ electrode exhibited a dominant diffusion-controlled contribution of approximately 85%, with a capacitive contribution of about 15%. Conversely, at a higher scan rate of 100 mV s⁻¹, the capacitive contribution increased markedly to ~65%, as shown in Figure 4d. This transition highlights that surface-controlled pseudocapacitive processes become increasingly dominant at elevated scan rates, owing to enhanced charge accessibility and reduced ion diffusion limitations [44,45].

The practical applicability of the synthesized PPy–WS₂ nanocomposite was demonstrated by fabricating the gel electrolyte-based asymmetric supercapacitor device, employing PPy–WS₂ as the anode, activated carbon (AC) as the cathode, and a PVA/KOH gel electrolyte. The assembled device, denoted as PPy–WS₂//AC, was systematically evaluated for its electrochemical performance. The cyclic voltammetry curves of the PPy–WS₂//AC device, recorded at various scan rates (Figure 5a), exhibit a combination of redox peaks and quasi-rectangular shapes, indicative of hybrid charge-storage behaviour arising from the pseudocapacitive contribution of PPy–WS₂ and the electric double-layer capacitance of AC. The CV profiles retain their overall shape with increasing scan rate, confirming good electrochemical reversibility and stable device operation. Galvanostatic charge–discharge measurements performed at different current densities (Figure 5b) reveal non-linear, quasi-triangular charge–discharge curves with a noticeable initial voltage drop (IR drop), further validating the hybrid nature of the device. The PPy–WS₂//AC device delivers a specific capacitance of 133 F g⁻¹ at a current density of 2 A g⁻¹. In addition, it achieves a high energy density of 41.6 Wh kg⁻¹ at a power density of 1500 W kg⁻¹, underscoring its potential for high-performance energy storage applications.

Electrochemical impedance spectroscopy analysis (Figure 5c) provides further insight into the internal resistance and charge-transfer properties of the device. Equivalent circuit fitting yields a solution resistance (R_s) of 1.2 Ω and a charge-transfer resistance (R_ct) of 3.4 Ω. These values are relatively higher than those observed in the three-electrode configuration, primarily due to the polymeric PVA/KOH gel electrolyte, which partially restricts ion mobility. Nevertheless, the gel electrolyte offers significant advantages, including the elimination of electrolyte leakage, improved device safety, and the ability to construct compact and flexible architectures compared to conventional liquid-electrolyte systems. Collectively, these features establish the PPy–WS₂//AC device as a promising candidate for practical and wearable energy storage applications.

The long-term electrochemical stability of the fabricated PPy–WS₂//AC asymmetric supercapacitor device was assessed through continuous charge–discharge cycling over 10,000 cycles shown in Figure 5d. The device exhibits stability, retaining 105% of its initial specific capacitance after 2500 cycles at 5 Ag⁻¹, thereby confirming stable electrochemical performance under extended operation. This high capacitance retention highlights the effective synergy between the PPy–WS₂ positive electrode and the AC negative electrode within the solid-state configuration. The improved cycling stability is primarily attributed to the PVA/KOH gel electrolyte, which ensures a stable electrode–electrolyte interface while minimizing electrolyte evaporation and leakage during prolonged cycling. Moreover, the gel electrolyte accommodates volume fluctuations in the electrode materials, thereby alleviating mechanical stress and mitigating structural degradation. The Ragone plot of the fabricated supercapacitor device, shown in Figure 5e, illustrates the relationship between energy density and power density at different current densities. The device achieves a maximum energy density of 41.6 Wh kg⁻¹ at a current density of 2 A g⁻¹, which gradually decreases to 20 Wh kg⁻¹ at 10 A g⁻¹ due to increased polarization and restricted ion diffusion at higher charge–discharge rates. Importantly, the device maintains a favourable balance between energy and power densities, highlighting its capability for high-rate performance. The practical applicability of the assembled PPy–WS₂//AC device was further demonstrated by successfully powering a light-emitting diode (LED), as shown in Figure 5f, thereby confirming its potential for real-world energy storage applications. The details of comparison of results have been presented in

Table 1. Comparison of synthesized PPy–WS₂ composite performance with the literature.

Material	Synthesis Method	Electrode Performance	Device Performance	Reference
WS2	Hydrothermal method	361 Fg−1 at 2 mVs−1	Energy density 14 Wh kg−1 power density 0.8 kWkg−1	[46]
PCF-rGO-ppy	Dip coating method	NA	328.91 Fg−1 at 0.5 Ag−1, 29.234 Wh kg−1 power density 4000 Wkg−1	[47]
WS2/rGO composite	Solvothermal method	230 Fg−1 at 1 Ag−1, retaining 83.59% of its initial capacitance after 10,000 charge–discharge cycles	Not available	[48]
V2CTX/WS2 composite	Ultrasonication method	1216.34 Fg−1 at 1 Ag−1,	Energy density 111.1 Wh kg−1 power density 9599.2 Wkg−1	[49]
PPy–WS2 composite	Oxidative polymerization	816 Fg−1 at 1 mVs−1	Energy density 41.6 Wh kg−1 power density 1500 Wkg−1	Present work

.

4. Conclusions

A polypyrrole–tungsten sulfide (PPy–WS₂) nanocomposite was synthesized through an oxidative polymerization approach and investigated for use in supercapacitors. Detailed structural, morphological, and compositional analyses confirmed the successful integration of WS₂ within the PPy framework, yielding favourable physicochemical properties. Electrochemical evaluation using cyclic voltammetry, galvanostatic charge–discharge, and impedance spectroscopy demonstrated outstanding capacitive performance, with a maximum specific capacitance of 816 F g⁻¹ at 1 mVs⁻¹ and excellent cycling stability. To assess device-level applicability, an asymmetric supercapacitor was constructed employing PPy–WS₂ as the positive electrode, activated carbon as the negative electrode, and a PVA/KOH gel electrolyte. The assembled PPy–WS₂//AC device achieved an energy density of 41.6 Wh kg⁻¹ and a power density of 1500 W kg⁻¹, while maintaining 105% of its initial capacitance after 2500 charge–discharge cycles, confirming remarkable long-term durability. The prototype was further able to power a light-emitting diode, highlighting the practical potential of PPy–WS₂ nanocomposites as promising candidates for advanced energy storage technologies.