Construction And Properties Of MnO₂Enriched V₂O₅/Polymer Coaxial Nanowires

With the rapid development of biotechnology, energy, environment, advanced manufacturing technology, new requirements about the synthesis and properties of materials have been proposed. Single structured materials have been far from satisfying the demands of the application of materials, and thus the development of heterostructured composites formed by optimized combination of multistructured materials is in great needs, which can regulate the physical and chemical properties of materials to meet new and special application. As a typical layered metal oxide, one-dimensional vanadium oxide nanomaterial has gained extensive attention and study due to its good lithium intercalation performance. Among them vanadium pentoxide(V2O5) is one of the earliest studied cathode materials of lithium ion battery, which has large capacity and high energy density. But in practice, V2O5as cathode materials still has some disadvantages such as low conductivity, fast capacity fading and poor reversible cyclability. As a result, the modification research of one-dimensional vanadium oxide electrode material is the cross and forward energy technology and nanotechnology.Here, the MnO2enriched V2O5/polymer coaxial nanowires are constructed by in situ chemical oxidative polymerization and redox exchange. V2O5nanowires were chosen as the substrate nanowires and poly-3,4-ethylenedioxythiophene (PEDOT) and polyaniline (PANI) were chosen as the polymer. The structure and morphology of the products were characterized and their electrochemical performance were investigated to explore the influence of the heterostructure on the electrochemical performance of V2O5nanowire electrode materials. The major results are summarized as follows:V2O5nanowires were prepared by hydrothermal reaction followed by annealing treatment, the polymer layer coated on V2O5nanowires by in situ chemical oxidative polymerization and MnO2nanoparticles were loaded on the surface of V2O5/polymer nanowires by redox reaction. After that, lithium-ion batteries were assembled by V2O5/polymer&MnO2nanowires as the cathode active material. Structures of these composite nanowires were characterized by fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and etc. Constant-current charge and discharge and cyclic voltammetry were used to explore the electrochemical properties such as charge-discharge capacity, cycling performance, lithium ion diffusion and so on. Compared with pure V2O5nanowires, heterostructured V2O5/polymer&MnO2nanowires show distinct improvement of battery performance. Test results show that both the conductive polymer coating and MnO2loading can increase the conductivity of the active materials and the specific surface area in contact with the electrolyte, thus leading to a significant improvement of the cycle stability and structure stability. While under the current density of50mA/g, the initial and the40th discharge capacities of V2O5/PEDOT&MnO2can reach179.2and166.1mAh/g, respectively, corresponding to a capacity fading of only0.19%per cycle and the V2O5/PANI&MnO2also shows good cycle and structure stability.