The Design And Performance Study Of Vanadate Nanowire Arrays Cathode For Li-Ion Batteries

The use of fossil fuels causes environment pollution and depletion of resources.Lithium ion batteries have the advantages of high energy density and long cycle life,which is one of the effective approaches to solve the energy problems.Vanadium oxide is a typical layered nanomaterial,which makes it process a open structure for the insertion of lithium ion.However,the defects of the vanadium oxide are low conductivity,and the poor structure stability during lithium interaction/deintercation.To overcome the limitations mentioned above,one approach is vanadium-based nanowires intercalated with metal ions,another is a mixed conducting network fromed by carbonaceous materials.In this paper,sodium vanadate(Na₅V₁₂O₃₂)nanowire arrays,iron vanadate(Fe_0.12V₂O₅)nanowire arrays,lithium vanadate@reduce graphene oxide(Li_0.04V₂O₅@rGO)nanocomposites,Potassium Vanadate?KVO?nanowire arrays were successfully prepared by using one-step solution heat method with subsequent calcinations.Furthermore,the electrochemical performances of these nanomaterials as cathode for lithium ion batteries were investigated.The structure and morphology of the Na₅V₁₂O₃₂ nanowire were characterized by XRD,SEM,TEM,and the length of the nanowire is about 10.5 ?m.The unique architecture renders a high-rate transportation of lithium ions that is attributed to the active materials connected to the current collector directly.In this paper,the electrochemical properties of the samples with different reaction times and annealed temperatures were compared and the reaction time of 1 h and calcinations temperature of 250 oC was the best.The Na₅V₁₂O₃₂ nanowire arrays as electrodes for lithium ion batteries exhibit a significant capacity stability with a capacity from 339 to 289 mAh g-1 in 50 cycles at 50 mA g-1 and the capacity retention is 85 %.The morphology of the Fe_0.12V₂O₅ was characterized by SEM and TEM,which demonstrated the nanowires is porous.And the Fe_0.12V₂O₅ nanowires are about 30 nm in diameter and several micrometers in length.The effect of reaction time on the resulting morphology is investigated and the mechanism for the nanowire formation is proposed.As an electrode material used in lithium ion batteries,the discharge capacity of the electrode is 278 mAh g-1 and the capacity rention is 89 % after 100 cycles in the voltage range of 2.0-3.6 V.When the voltage range is expanded to 1.0-4.0 V,the discharge capacity is 289 mAh g-1 after 500 cycles at 500 mA g-1.Li_0.04V₂O₅ nanowires are densely anchored onto reduced graphene oxide?rGO?nanosheets to form Li_0.04V₂O₅@rGO nanocomposite.Due to this unique structure,the Li_0.04V₂O₅@rGO exhibits remarkable rate performance and excellent cycling stability.The charge transfer resistance of Li_0.04V₂O₅ and Li_0.04V₂O₅@rGO transfer from 178 ? to 81 ?.It delivers a reversible discharge capacity of 738 mAh g-1 at current density of 100 mA g-1.After 500 cycles,it still maintains a high capacity of 731 mAh g-1.The morphology,crystalline structure and component of the KVO nanowire grown on Ti fabric were characterized by SEM,TEM,XRD,XPS.When the flexible electrode tested as cathode materials for lithium ion batteries,the KVO electrode has a high reversible capacity of 270 mAh g-1 at a current density of 100 mA g-1 after 300 cycles.Furthermore,the KVO delivers outstanding rate behavior,even at 960 mA g-1,a reversible capacity as high as 214 mAh g-1 can be retained.