High-Performance Asymmetric Supercapacitor Based on Ternary MnO2-Polyaniline-Reduced Graphene Oxide Quantum Dots Nanocomposite Electrode

A ternary nanocomposite of manganese dioxide-reduced graphene oxide quantum dot-polyaniline (MGP) was designed and fabricated via a facile chemical method. Using different spectroscopy and microscopy methods, morphology and structure of this nanocomposite were studied. Also, electrochemical measurements demonstrated a high specific capacitance of 423 F g −1 at a current density of 5.7 A g −1 in a three-electrode configuration. It was found that specific capacitance of the nanocomposite electrode is much higher than that of each single component of nanocomposite. In addition, capacitance retention of almost 85% of the initial capacitance was preserved after 2000 charge–discharge cycles, indicating considerable cycling stability. An asymmetric device was also fabricated based on MGP nanocomposite as the positive electrode and graphene oxide as the negative electrode. More importantly, the asymmetric supercapacitor offered a high energy density without considerable decrease in the power density. This asymmetric supercapacitor showed a capacitance retention of 90% after 2000 successive operational cycles. Such an excellent electrochemical performance of the ternary nanocomposite can be attributed to synergistic effects between individual components and its well-designed nano-networked structure.