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Summary: Polypyrrole (PPy)‐based composites containing nanostructured VOx, PbOx, and MnOx are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm2) formed as a result of the intercalation with their metals. Both intercalation and synthesis are performed in the synthesis solution containing metal(II)tetrafluoroborate salts, pyrrole monomer, HBF4, H2O, Triton‐X 100 (TX100), and carboxymethyl cellulose (CMC). The mass loading of the composite at the electrode is maintained at 10 mg cm−2. Symmetric and asymmetric unit cells are prepared in polyvinyl alcohol (PVA)/H2SO4 (1:1) gel electrolyte using composites synthesized on the treated graphite paper electrode. The electrical properties of these cells are examined by electrochemical impedance spectroscopy and their capacitive properties by cyclic voltammetry and galvanostatic‐charge discharge test. The asymmetrical cell, prepared with PPy/PbOx/CMC composite having energy density and cycle life better than others, exhibits 7.77 Wh kg−1 and 0.51 kW kg−1 at a working voltage of 1.4 V, considering the total mass of all sub‐components. The three‐cell asymmetric stack design, which is prepared using these composite‐coated electrodes, achieves a coulombic efficiency of 76% at 4.2 V. Finally, an electronic control system (DC/DC buck‐boost converter) is designed and implemented to manage the charge and discharge cycles of single‐cell and bipolarly connected stack to operate the asymmetric supercapacitor arrays with high performance. [ABSTRACT FROM AUTHOR]

Abstract In the present study, the polypyrrole (PPy) composites with nano-structured CoO x , NiO x , MnO x , and FeO x were synthesized using the galvanostatic method on their own metal-intercalated graphite surfaces. The deposition and intercalation are performed in TBABF 4 /acetonitrile solution with related metal (II) tetrafluoroborate salts, pyrrole, HBF 4 , H 2 O, Triton-X 100 (TX100) and carboxymethyl cellulose (Na-CMC). For the PPy/MnO x /Na-CMC composite, the effects of intercalation and additives on the specific capacitance were examined in an H 2 SO 4 /water medium by using cyclic voltammetry (CV) and the Electrochemical Impedance Spectroscopy (EIS). Using the optimum deposition conditions determined for Mn composite (additive concentrations and galvanostatic parameters), PPy/CoO x /Na-CMC, PPy/NiO x /Na-CMC, and PPy/FeO x /Na-CMC coatings with a mass loading of 4.0 mg cm−2 were deposited on their own metal-intercalated graphite electrodes in the deposition solutions containing Co(BF 4) 2 , Ni(BF 4) 2 and Fe(BF 4) 2 , respectively. XRD, TEM, XPS, SEM-EDX, BET, and EIS techniques were used in characterizing the coatings. Subsequently, the capacitive properties of the composite coatings were examined by means of the galvanostatic charge-discharge test. The highest SC value is recorded for the Mn-based composite (463 F g−1), whereas the lowest is for Fe-based (311 F g−1) one. Finally, symmetric and asymmetric supercapacitor configurations incorporating two electrodes with 10 mg cm−2 active material were used in making measurements to determine the capacitive behaviors of PPy/Metal oxide composites. The symmetric supercapacitor with PPy/MnO x /Na-CMC composite providing 0.29 kW kg−1 and 15.0 Wh.kg−1 at 0.5 A g−1 maintains 62% of its power and energy densities at 2.5 A g−1 at the end of 5000 cycles at a potential range of 0.8 V. [ABSTRACT FROM AUTHOR]

One-step electrochemical synthesis of polypyrrole-vanadium oxide (PPy-VOx) composites was performed on the Vanadium-intercalated pencil graphite (PG) surface in an acetonitrile solution with the presence of carboxymethyl cellulose (CMC). Both intercalated surface and composite coating were characterized using SEM-EDX Spectroscopy and X-Ray Diffraction (XRD) techniques. The capacitive properties of the coating were elaborated in an H 2 SO 4 /water medium using galvanostatic charge–discharge, potential cycling, and electrochemical impedance spectroscopy methods in comparison with the coatings prepared without additives. While V-intercalation provides a significant increase in the specific capacitance, the carboxymethyl cellulose enhances the cyclic performance of the composite. The improvement at the capacitance of the composite may be due to the homogenous distribution as well as the synergetic effect between PPy and VO x . The capacitive properties were studied in aqueous solutions of H 2 SO 4 and Li 2 SO 4 , and in an acetonitrile solution of HBF 4 /TBABF 4 . The specific capacitance value of the composite coating on the V-intercalated pencil graphite was determined as 204 F g −1 in an acetonitrile solution of HBF 4 /TBABF 4 for a mass loading of 10.0 mg cm −2  at 2.0 A g −1 , when the capacitance of bare graphite was subtracted. The two-electrode supercapacitors composed of both asymmetric and symmetric configurations were also prepared and examined in an acetonitrile/adiponitrile solution of HBF 4 /TBABF 4 . The charge–discharge results for asymmetric supercapacitor reveal that the PPy-VO x -CMC composite coating (20 mg cm −2 ) on V-intercalated graphite paper represents a high energy density of 18 Wh.kg −1 and a high power density of 0.43 kW kg -1  at 0.5 A g −1 , as well as a stable cycle life at the potential range of 1.2 V. [ABSTRACT FROM AUTHOR]

The study depicts a one-step electrochemical synthesis of composite based on polypyrrole (PPy) and SbO x (Sb 2 O 3 , Sb 2 O 5) on the graphite surface for the supercapacitor electrode in an acetonitrile solution including pyrrole monomer and Sb(BF 4) 3. PPy/SbO x composite on graphite plate is characterized using XPS, XRD, TEM, BET, and FESEM by comparing it with PPy homopolymer prepared in the same way. SbO x forms in nano-size and homogeneously encapsulates in PPy due to their simultaneous synthesis. The average pore size of the composite coating is 23.9 nm. The coated PG electrodes are tested in an H 2 SO 4 electrolyte using CV, EIS, and GCD methods. SbO x nanoparticles enhance the capacitive performance of PPy due to the contribution of its catalytic and pseudocapacitive properties. The specific capacitance of the PPy/SbO x -coated PG electrode is 389.5 F g−1 at 5 A g−1 for 1.0 mg cm−2 loading. PPy/SbO x is synthesized in the presence of carboxymethyl cellulose (CMC) to provide stability to the coating. An asymmetric supercapacitor cell is fabricated by assembling the PPy/SbO x /CMC-coated and activated carbon-based graphite paper electrodes (10 mg cm−2 loading). While the potential window expands to 1.4 V, it delivers an energy density of 8.3 Wh kg−1, a power density of 3.5 kW kg−1, and a coulombic efficiency of 90% at 5 A g−1. Post-mortem analysis reveals that structural degradation of PPy in the composite limits long-term stability. • PPy and SbO x are cosynthesized at one step on graphite from Py and Sb(BF 4) 3 in acetonitrile. • TEM results show the encapsulation of SbO x (Sb(III) and Sb(V)) into the growing PPy. • 1.3% nano-sized SbO x dispersed uniformly in composite enhances specific capacitance. • Fabricated asymmetric supercapacitor cell delivers 3.5 kW kg− 1 and 8.3 Wh kg− 1 at 5 A g-1. • Cell displays a nearly rectangular shape at a 1.4 V potential window with 90% efficiency. [ABSTRACT FROM AUTHOR]