Electrosynthesis of binder-free polypyrrole/nano- Bi2O3-Bi2O2CO3 composite for supercapacitor anode

Abstract

β-Bi2O3-Bi2O2CO3 dispersed polypyrrole (PPy/β-Bi2O3-Bi2O2CO3) composite is electrochemically deposited on stainless steel mesh (SSM) surface in an acetonitrile solution of pyrrole monomer and pre-synthesized β-Bi2O3-Bi2O2CO3 nanoparticles. The coating is characterized compared with those of the PPy homopolymer coating and β-Bi2O3-Bi2O2CO3 powder using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), XPS, XRD, TEM, and FESEM. Flower-shaped spherical nanoparticles containing β-Bi2O3-Bi2O2CO3 phases are encapsulated in the partially oxidized PPy clusters composed of small nanospheres, thus dispersed well in the composite. The PPy/β-Bi2O3-Bi2O2CO3 coating exhibits a more capacitive behaviour than the PPy coating due to the electro-generation of Bi5+ in the β-Bi2O3-Bi2O2CO3 phases during the synthesis of composite and the supercapacitor cycling. The coated electrode provides a higher pseudocapacitive contribution (67.4 %) thanks to the mixed metal oxide of β-Bi2O3-Bi2O2CO3 in addition to PPy, exhibited a specific capacitance of 360 F g−1 in 100 mM Li2SO4. Bi2O2CO3 with a layered structure contributes to enlarge of active surface area, conductivity, and catalytic performance. A solid-state asymmetric cell is fabricated with polyvinyl alcohol (PVA)/Li2SO4 using 10 mg cm−2 mass-loaded PPy/β-Bi2O3-Bi2O2CO3 composite- and polyvinyl chloride (PVC)/carbon- coated SSM electrodes. The device provides 64.2 Wh kg−1 specific energy and 350 W kg−1 specific power at 0.5 A g−1 with a coulombic efficiency of 90 % and high stability of about 97 % for 5000 cycles. The electrode has the potential to be used as a binder-free electrode in high-performance supercapacitors.