Research On Doping Modification And Lithium Storage Performance Of V₂O₅ And VO₂（B）

The rapid growth of portable mobile electronic devices and new energy electric vehicles has led to a new round of advancement in lithium-ion batteries（LIBs）.The cathode material,which determines both the lithium storage capacity and the cost,has naturally become a top priority for research.With a special layered structure,vanadium oxide can be considered as a potent contender for next-generation lithium-ion battery cathode materials owing to its high theoretical capacity,lower cost and abundant reserves.However,the electrostatic interaction between the metal ions and the host material during the process of detachment/embedding will affect the stability of the material structure and lead to the capacity degradation of the cathode material;in addition,inorganic metal oxides have poor electrical conductivity and poor cycling performance when used as cathode materials for lithium-ion batteries.In this paper,V₂O₅and VO₂（B）were selected as the research objects for doping modification,and demonstrated that their lithium storage performance can be effectively improved after doping treatment.（1）V₂O₅nanoplatelets was prepared by a simple hydrothermal method combined with thermal treatment,and by adjusting the length of the calcination time,V⁴⁺-doped V₂O₅was obtained.The presence of V⁴⁺expands the cell size of V₂O₅,which can accommodate more Li⁺in charge/discharge;the introduced oxygen vacancies facilitate structural stability during cycling.Even at an ultra-high current density of 4A g^-1,the V⁴⁺-doped V₂O₅still has a high specific capacity of 158.9 m Ah g^-1and a residual capacity of 100.0 m Ah g^-1after 300 cycles.（2）To improve the lithium storage performance of V₂O₅and VO₂（B）,Mn ion-doped V₂O₅and VO₂（B）nanorod materials were synthesized by hydrothermal method.The results showed that the doping of Mn ions effectively improved the electrical conductivity and lithium storage activity of V₂O₅and VO₂（B）materials,and reduced the electrochemical reaction impedance of the materials.When Mn-V₂O₅was used as the cathode material for LIBs,the initial capacity was as high as 313.9 m Ah g^-1at a current density of 100 m A g^-1.When Mn-VO₂was used as the cathode material for LIBs,the capacity was still as high as 175.8 m Ah g^-1at a high current density of 1 A g^-1with a retention rate of 72.7%after 300 cycles.（3）The CO₂-modified VO₂（B）nanorods was synthesized by reducing V₂O₅using excess oxalic acid in a hydrothermal process,which decomposed under high temperature and pressure to produce CO₂,and successfully introduced CO₂small molecules into the structural framework of VO₂（B）.In VO₂（B）structure,CO₂plays a"pillar"role,which expands the tunnel structure,and forms a weak electrostatic interaction between O_CO2and lithium ions,which accelerates the diffusion of lithium ions.The CO₂-doped VO₂（B）has a high specific capacity of 251.1 m Ah g^-1when used as a cathode material for LIBs and remains a high capacity as 170.0 m Ah g^-1,even at a high current density of 1 A g^-1.