Fabrication And Electrochemical Properties Of Three-dimensional Hybrids Composed Of Tungsten Oxides/Sulfides Supported On Reduced Graphene Oxide

This work was based on constructing 3D structure of the hybrids of tungsten based nano compound and graphene as well as investigating the facile and effective methods of synthesis and the relationships between the electrochemical properties and the components and structures of the materials.First,we synthesis the hybrids of WO3·0.33H2O and nitrogen-doped reduced graphene oxide(WO3·0.33H2O/N-rGO)through the simple one-step solution combustion method,and applied it into the anode of lithium ion batteries as well as comparing with pure WO3·0.33H2O and N-rGO made by the similar process in the structures and properties.Second,W18O49/N-rGO was obtained by high temperature reduction of WO3·0.33H2O/N-rGO made though solution combustion method,which would improve the conductivity and 3D structure of the hybrid as well as the performance in lithium ion batteries anodes.Inaddition,the different content of N-rGO in the W18O49/N-rGO hybrid were also synthesized to investigate and analyze the impact of N-rGO content in the hybrids and corresponding lithium ion batteries anodes performance,which demonstrate the best proportion of the W18O49/N-rGO hybrid.Last but not least,the hybrid of tungsten disulfide and nitrogen and sulphur co-doped reduced graphene oxide(WS2/N,S-rGO)was synthesized by high temperature sulfuration process,of which the aquous supercapacitors properties were investigated and analyzed in detail,demonstrating the superior perfoamance of WS2/N,S-rGO hybrid as the electrode materials in supercapacitors.It was testified that WO3·0.33H2O nanoparticles could uniformly combined with N-rGO nanoflakes through solution combustion methods.As the lithium ion batteries anode material,WO3·0.33H2O/N-rGO hybrid exhibited the specific capacitiy of 469.2 mAh g"1 after 100 cycles at 100 mA g"1,which certainly displayed synergistic effect comparing with the performance of pure WO3·0.33H2O and N-rGO.While the W18O49/N-rGO hybrid performed apparently improved capacitance as the W18O49/10%N-rGO exhibited 333.55 mAh g-1 at the current density of 1600 mA g-1 and 604.4 mAh g-1 after 100 cycles at 100 mA g-1,which was 82.67%of the discharge capacitance of second cycle,demonstrating high cycling stabilities and superior rate capabilities.After the high temperature sufulration process,the WO3·0.33H2O/N-rGO changed into the WS2/N,S-rGO hybrid composed of WS2 nanoflakes and layered N,S-rGO,which exhibited 1562.5 F g-1 at the current density of 1 A g-1 and even retained 780 F g-1 at 40 A g-1 in 6 M KOH,displaying superior capacitance and rate capabilitiy.WS2/N,S-rGO//AC asymmetric supercapacitor(ASC)was also made by utilizing the WS2/N,S-rGO as the positive material and active carbon(AC)as the negative material,which showed an energy density of 31.19 Wh kg-1at the power density of 58.39 Wkg-1 and still retained 17.11 Wh kg-1 at 1944.44 W kg-1,demonstrating that the WS2/N,S-rGO was an excellent electrode material for supercapcitors.In summary,WO3·0.33H2O/N-rGO had ben successfully synthesized through solution combustion method.While the Wi8O49/N-rGO and WS2/N,S-rGO were also obtained by the subsequent high temperature reduction or sulfuration process.The preparation methods were simple and of high efficiency.It was demonstrated that the W18O49/N-rGO possessed good capacities in lithium ion batteries anodes and the WS2/N,S-rGO showed excellent porperties in supercapacitors applications.