The synthesis of polypyrrole@Mn3O4/reduced graphene oxide anode with improved coulombic efficiency

• A two-step method is employed to fabricate polypyrrole@Mn3O4/reduced graphene oxide electrodes.
• The electrodes coated with polypyrrole deliver a coulombic efficiency of ca.70%.
• The composites deliver an initial discharge capacity of ca.1600 mAh g−1 at 60 mA g−1.

A two-step method consisting of an in-situ transformation and an in-situ oxidative polymerization is employed to fabricate polypyrrole@Mn3O4/reduced graphene oxide composites. The resulting materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman. The XRD analysis reveals the formation of Mn3O4/reduced graphene oxide and polypyrrole@Mn3O4/reduced graphene oxide. Mn3O4 particles coated with reduced graphene oxide and polypyrrole get an average diameter of ca.27 nm. The TEM images of polypyrrole@Mn3O4/reduced graphene oxide demonstrate that Mn3O4/reduced graphene oxide nanocomposites are indeed coated by a transparent polypyrrole film. The FT-IR studies disclose the characteristic functional groups between the respective materials. Moreover, Raman measurements confirm the reduction of graphite oxide to reduced graphene oxide. The result of electrochemical measurement demonstrates that it gets a high initial discharge capacity of ca.1600 mAh g−1 at 60 mA g−1 and the initial charge/discharge efficiency delivers a nice optimization after coated with polypyrrole (ca.45% VS ca.70%). The capacity of polypyrrole@Mn3O4/reduced graphene oxide can maintain at a level of ca.1000 mAh g−1 in the first five cycles and the rate performance of it is much better than that of Mn3O4/graphene.

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