Construction, Structure And Properties Of Silver Vanadium Oxide/Polymer Coaxial Nanocables

Coaxial nanocables can not only combine advantages of both core layer and shell layer, but also exhibit new properties by the heterointerfaces and synergistic effects. Therefore, it is very valuable to study coaxial nanocables. Due to layered structures and various oxidation states of vanadium, Silver vanadium oxides (SVO) have unique ion characteristics and electrochemical properties, and shows wide application in lithium ion battery cathode materials. But in practice, silver vanadium oxide cathode materials still have some disadvantages such as low conductivity, fast capacity fading and poor reversible cyclability. Conducting polymers such as polypyrrole (PPy), polyaniline (PANI), have attractive application prospects in the field of electrochemistry because of their good air stability, high conductivity, environmentally non-toxic, reversible redox properties and easy doping. In the thesis, the main research objects are focused on silver vanadium oxide/polymer coaxial nanocables. The structure and properties of the nanomaterials mentioned above were investigated by XRD, FTIR, FESEM, TEM,Ⅰ-Ⅴtesting, galvanostatic current charge and discharge, cyclic voltammetry and AC impedance. The main contents and results are as follows:Silver vanadium oxide/polymer coaxial nanocables were successfully constructed by a nanowire-based two-step method. First,β-AgVO3 nanowires with high yield, good morphology and structure were successfully assembled by rheological self-assembling method and simple hydrothermal method. Then, pyrrole or aniline was polymerized on the surface of dispersedβ-AgVO3 nanowires by the method of chemical oxidative polymerization, forming AgVO3/PPy and AgVO3/PANI coaxial nanocables, with the thickness of shell about 6～16 nm. Acidic medium, too much monomer dosage or too long reaction time easily leaded to formation of Ag impurities and damage of the body materials.Lithium-ion batteries were assembled using coaxial nanocables as cathode active materials. Galvanostatic current charge and discharge, cyclic voltammetry, AC impedance method were used to study the charge and discharge properties, cyclic reversibility and lithium ion diffusion of the coaxial nanocable materials. Compared with pureβ-AgVO3 nanowires, both PPy and PANI coating could improve battery performances. Among them, AgVO3/PANI nanocables showed the best electrochemical performance, while AgVO3/PPy nanocables constructed with (NH4)2S2O8 as oxidant showed higher performance improvement than those with AgVO3 as oxidant. At the same time, the amount of polymer shouldn't be too large, or it would have adverse effects to the electrochemical properties. The electrochemical properties were influenced by the characteristics of coating polymer and different structural and composition of products. TheⅠ-Ⅴresults showed that the improvement of the electrochemical properties of coaxial nanocables had some relationship with the improvement of their electrical conductivity.