Preperation And Electrochemical Performance Of Low Valence Vanadium Oxide Nano-composite Materials

Rechargeable lithium batteries (LIBs) and supercapacitors(SCs) have attractedintensive attentions due to the ever increasing market for electrochemical devices withadvanced energy conversion and storage performance. In order to meet therequirements of various new emerging device, the next generation of LIBs and SCs areexpected to not only own high capacity performance, but also perform an excellentcycling stability and a high rate ability, significant research challenges andopportunities exist for the design and fabrication of anode electrode materials, whichplay a crucial part in enhancing of the whole lithium cell. Act as electrode materials toreplace the traditional graphite, vanadium sesquioxide (V2O3) and vanadium dioxide(VO2) has attracted much attention recently because of its high capacity, broadpotential windows, layer structure beneficial to embed into ion. However, because ofthe intrinsic low conductivity, the V2O3and VO2suffer from poor rate capabilitywhich greatly limits its further application. To V2O3and VO2coated with conductivecarbon can overcome these disadvantages and improved the rate performance. Inadditional, formation a semi-hollow nanocomposites such as yolk-shell, peapodstructure can release the large volume changes resulting from the charge/dischargeprocess and improve cycling stability.The main research contents are as follows:(1) Fabrication peapod-like V2O3@C ultralong namowire heterostructure withinternal void spacewas carried out by annealing the V3O7H2O@C nanowirescore/shell nanostructure in an inert gas. Such particular peapod-like V2O3@Cheterostructure can release volumetric expansion during the Li+insertion/extraction,and resuting in excellent cycle stability. The outer coating carbon long nanotube alsoprovides a fast transfer channel of lithium ion and the rate performance.(2) VO2nanobelt sheet coated by graphene nanocompsites was prepared byhydrothermal method with V2O5and graphene oxide (VO2/Graphene). VO2has alayered structure to beneficial to embed into Li+to generate intercalationpseudo-capacity and greatly improve the energy density of the composite materials.Graphene sheet combined with VO2nanobelt can prevent the electrochemicaldissolution and improve the conduction of VO2, and effective improve rateperformance, cyclic stability of VO2/Graphene composites.