Preparation And Electrochemical Capacitance Performance Of Carbon Nanomaterials And Their Composites

Supercapacitor is one of the most prominent energy storage devices due to its high power density and long cycle life. As the electrode materials of supercapacitor, unitary materials are hard to achieve excellent electrochemical performance due to their intrinsic defects. Therfore, nanocomposites which combine the superiorities of varied materials become a research hotspot. In this study, carbon nanomaterials with specific morphologies were prepared through modifying graphene and multi-walled carbon nanotubes?MWCNTs?. And then, nanocomposites based on these modified carbon materials were synthesized to improve the electrochemical property. The main research contents and results are summarized as follows:?1? Oxidized curly graphene nanoribbon ?OCGNR? was prepared using a modified Hummers' method through tailoring MWCNTs transversely and longitudinally. PANI was synthesized by in-situ polymerizing aniline in the suspension of OCGNR. Afterwards, MnO2 nanoneedles were interspersed in the OCGNR/PANI composite by a hydrothermal process. Finally, hydrazine monohydrate?N2H4·H2O? was used to reduce OCGNR/PANI/MnO2 to CGNR/PANI/MnO2. The research result shows that the composite exhibits excellent electrochemical performance when the amount of MnO2 is 16 wt% which delivers a high specific capacitance of 496 F g^-1 at 1 A g^-1 in the three-electrode system. What's more,81.1% of its initial capacitance is retained after 5000 cycles at a scan rate of 50 mV s^-1. CGNR/PANI/MnO2 is also evaluated via a two-electrode configuration and exhibits a specific capacitance of 103 F g^-1 at 0.5 A g^-1. Furthermore, the composite shows a energy density of 11.3 Wh kg^-1 at power density of 2.5 kW kg^-1. All the results indicate that CGNR/PANI/MnO2 is a promising electrode material.?2? Aniline was in-situ polymerized in the homogeneous suspension of GO/OCGNR. And then, RGO/OCGNR/PANI was reduced to RGO/CGNR/PANI by N2H4·H2O. Electrochemical measurement displays that the specific capacitance of composite can reach 405 F g^-1 at 1 A g^-1 in the three-electrode system and showed excellent capacitive property. It also delivers a specific capacitance of 71.3 F g^-1(0.5 A g^-1) in the two-electrode system. Moreover, the capacitor displays the highest energy density of 9.93 Wh kg^-1(at the power density of 250 W kg^-1) as well as long life with 80.5% specific capacitance retention after 2000 cycles.?3? Highly deformed graphene ?HDG? was successfully synthesized through a simple micro-explosion method. The morphology characterization indicates that HDG displays a fluffy morphology with more wrinkles and folded regions on the surface of deformed graphene. The results of XRD and BET show that deformed graphene can prevent the aggregation of the sheets. Electrochemical characterizations show that HDG exhibits a specific capacitance of 206 F g^-1 (1 A g^-1), which is much higher than that of RGO (118 F g^-1). Even at a high current density of 10 A g^-1, HDG also displays a capacitance of 152 F g^-1. Additionally, the electrode shows excellent cycling stability with 92.7% specific capacitance retention after 2000 cycles.