Preparation And Electrochemical Properties Of Graphene/Manganese Dioxide/Polyaniline Composites

In recent years, the study of energy storage materials research field has undergone a rapid growth prompted with the development of energy crisis and the electric vehicle industry. The supercapacitor is one of new energy storage devices, which mainly used for electric vehicles, uninterruptible power supply and other fields. However, to improve the specific capacity, rate capability and cycle stability are chanllenging. To overcome this obstacle, many composite materials have been utilized as electrods for improving the electrochemical performance of supercapacitor.In this work, the polyaniline was synthesized by interfacial polymerization method in the presence of HCl, HCSA and HCl O4. It is found that, the polyaniline molecular chains doped with HCl O4 have more orderly structure along the parallel and perpendicular to the chain direction, and have more conjugate structure in molecular chains.Electrochemical study shows that the polyaniline doped with HCl O4 have lower charge transfer resistance and higher specific capacity, the specific capacitystill up to 339 F/g at the current density of 5 A/g, exhibit also the best electrochemical performance.The crystalline Mn2O3, and Mn O2 with different nanostructured powers were prepared by sol-gel method.The effects ofp H values of the precursor solution,calcination temperature, heating rate and calcination time on the crystalline phase of the Mn2O3 powders were studied.The electrochemical performances of as-prepared porous Mn2O3 nanoplates used as anode materials in lithium ion batteries are investigated. It was found that such kind of Mn2O3 cansurpress the volume expansion during the lithium insertion/deinsertion processes, which has good cycling stability andhigh rate performance. The contents of graphene oxide template have an influence on the nanostructure of Mn O2. With the decrease of the amount of graphene oxide, the nanostructure of Mn O2 change from nanorods with 200 nm in length and 20 nm in diameter to nanoparticles of about 20 nm in diameter, and the crystalline state decreases, which change ?-Mn O2 to amorphous. The specific capacity and rate performance improve for increasing of specific surface of Mn O2 sample.In order to further improve the electrochemical performance of electrode materials, graphene/Mn O2 composite and graphene/Mn O2/polyaniline ternary composites were prepared. It was demonstrated that, the amount of Mn Cl2·4H2O and KMn O4 can affect the growth process of Mn O2 and further influence the nanostructure of Mn O2 formed during hydrothermal process. The Mn O2 nanosheets can evenly grow on the surface of graphene when the content of Mn Cl2·4H2O was 3 mmol, the specific capacity, rate performance and cycle stability of graphene/Mn O2 composites are obviously improved due to the increase of electronic conductivity.The graphene/Mn O2 composites can hinder the aggregation of polyaniline molecular chains when further combined with polyaniline. The graphene/Mn O2/polyaniline ternary composites show good rate performance due to the good contaction with electrolyte;The electrochemical properties of ternary composites change with the different ratio of Na2SO4 and H2SO4 in mixed electrolyte.In the Na2SO4 electrolyte, electrochemical properties of the composite decreased more severely.With the decrease of H2SO4 concentration, the specific capacity and rate performance of ternary composites decreased slightly. In the mixed electrolyte of 0.25 mol/L H2SO4 and 0.75 mol/L Na2SO4, the ternary composites show the best cycle stability.