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4.2 V Stack of metal oxide-polypyrrole-based composite electrodes and their power management

2020    Karaca, Erhan; Gokcen, Dincer; Pekmez, Nuran Ozcicek; Pekmez, Kadir; Ugur, Merve; Aksu, N. Dogancan

Polypyrrole (PPy)-based composites containing nanostructured VO x, PbO x, and MnO x are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm(2)) 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/PbO x/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.