Tungsten Oxide@Polypyrrole Core-Shell Nanowire Arrays as Novel Negative Electrodes for Asymmetric Supercapacitors

Among active pseudocapacitive materials, polypyrrole (PPy) is a promising electrode material in electrochemical capacitors. PPy-based materials research has thus far focused on its electrochemical performance as a positive electrode rather than as a negative electrode for asymmetric supercapacitors (ASCs). Here high-performance electrochemical supercapacitors are designed with tungsten oxide@PPy (WO3@PPy) core-shell nanowire arrays and Co(OH)(2) nanowires grown on carbon fibers. The WO3@PPy core-shell nanowire electrode exhibits a high capacitance (253 mF/cm(2)) in negative potentials (-1.0-0.0 V). The ASCs packaged with CF-Co(OH)(2) as a positive electrode and CF-WO3@PPy as a negative electrode display a high volumetric capacitance up to 2.865 F/cm(3) based on volume of the device, an energy density of 1.02 mWh/cm(3), and very good stability performance. These findings promote the application of PPy-based nanostructures as advanced negative electrodes for ASCs.