Preparation And Electrochemical Performance Of Vanadium Oxide Cathode Materials For Zinc Ion Battery

With the rapid development of modern society,the use of fossil fuels such as coal,oil,natural gas,etc.is increasing.The environmental pollution problems have become particularly serious.In this context,various consumer electron ic products have been obtained sufficient development opportunities.At present,the most widely used battery on the market is lithium-ion battery.However,the safety problems associated with the use of organic electrolytes in lithium-ion batteries are particularly serious.In addition,the reserves of lithium are limited,s o it is urgently need to develop renewable energies.Zinc ion batteries can perfectly solve the flammable and explosive safety hazards caused by organic electrolytes.However,the current research on zinc ion batteries is still in the initial stage.The positive electrode materials are relatively limited.At the same time,the specific capacity and the cycle stability under high current need to be solved urgently.Vanadium oxide has higher specific capacity and various species.The excellent cycle stability is favored by many researchers.From the perspective of exploring new electrode materials,this thesis adopts different preparation methods to prepare vanadium oxides and applies them to zinc-ion battery cathode materials.In this thesis we firstly use the hydrothermal reaction method to prepare nano-flaky vanadium oxide with a porous structure.The molecular formula of this oxide is Zn₃V₃O₈.With the constant current density of 0.5 A g^-1,the reversible specific capacity is 226.4 m Ah g^-1.For the stability test with a current density of 2 A g^-1,the capacity retention ratio after 3000 cycles is 95.9%.During the cyclic process the middle coulomb efficiency is maintained at 95%～105%.At the same time,it is found that the morphology of this material does not change significantly,and the analysis of the valence change of vanadium element verified its cyclic reversibility.Secondly,a new type of vanadium oxide is prepared by the dealloying method.Al and V are weighted at an atomic ratio of 85:15,then smelted,and stripped to finally obtain an aluminum-based alloy strip.After that we use 0.5 mol/L NaOH solution to corrode the aluminum and obtain an alloy compound with a molecular formula of Al₃V.Through a series of characterization methods we successfully verified the accuracy of the molecular formula.The resulting product is heated to finally obtain a mixture consisting of Al₃V coated with V₂O₅.The assembled battery was charged and discharged with a current of 0.05 A g^-1,and the capacity was 303.2 m Ah g^-1.For the stability test with a current density of 5 A g^-1,the capacity retention ratio was 86.1%after 2400 cycles.At the end of this thesis,we research the morphological changes and structural evolution of vanadium oxide during the charge and discharge process.XRD results at different voltages during each cycle shows the deviation and recovery process of the（001）crystal plane of V₂O₅.This thesis has not only broadened the scope of the types of cathode materials for zinc-ion batteries,but also provided a sufficient demonstration for the understanding of electrochemical behavior and mechanism.