Solvothermal Preparation And Electrochemical Properties Of VO₂（B） As Electrode

Magnesium rechargeable battery is expected to be next generation of high-energy green secondary battery.The cathode material with high-work-voltage and high-specific-energy is the development direction of Mg rechargeable battery.VO₂（B）cathode material has been widely studied and applied as lithium rechargeable battery cathode material because it has high working voltage and high specific energy,and it is a promising cathode material.In this paper,we synthesized VO₂（B）electrode material via solvothermal method,and the electrochemical performance of VO₂（B）as cathode material for magnesium rechargeable battery was investigated,and the Mg intercalation/deintercalation mechanism of VO₂（B）was explained from the kinetic point of view.Firstly,the preparation of VO₂（B）by solvothermal method was constructed.The effects of different temperature,reaction time and drying method on the electrochemical properties of the products were studied,and uses XRD and FESEM to characterize the structure and morphology of the electrode material under the optimal preparation conditions.The results show that the VO₂（B）nanosheets prepared by blast drying under conditions of 180℃,6h behaved the best electrochemical performance.Secondly,Electrochemical properties and mechanism of VO₂（B）Cathode materials were studied by electrochemical technique.VO₂（B）cathode material has a higher first discharge specific capacity about 461mAh/g under-1¹V（vs.Ag⁺/Ag）and-1⁰.2V（vs.Ag⁺/Ag）voltages with 100mA/g current density,which means 0.71mol of magnesium ion can be intercalated into one mole of VO₂（B）.Compared to most magnesium rechargeable battery cathode materials,it has a higher discharge voltage platform,which is about 2.15V(vs.Mg²⁺/Mg).VO₂（B）cathode material has more excellent rate performance at-1¹V（vs.Ag⁺/Ag）voltage range.When current density is increased to 1A/g,VO₂（B）exhibits difficulty in deintercalation of magnesium ions and exhibits capacitive characteristics.Diffusion coefficient of magnesium ions in VO₂（B）cathode material is 2.17x10^-10cm²/s,which is equivalent to lithium ion diffusion coefficient(10^-10cm²/s)of VO₂（B）nanowire cathode materials reported in literature.It has faster magnesium ion diffusion kinetics.In summary,VO₂（B）is a very promising cathode material.