Construction,Doping Modification And Lithium Storage Performance Of V₆O₁₃ And VO₂（B） Three-dimensional Micro-nano Structures

As an cathode material for lithium-ion batteries,vanadium oxide has gained much attention from academia owing to its significant advantages in terms of theoretical specific capacity,energy density and cost.Nevertheless,the specific capacity of vanadium oxide decays irreversibly during cycling due to its structural stability and poor electrical conductivity.In the present paper,a three-dimensional-micro-nano structure of vanadium oxide cathode material is constructed to enhance its stability;electrical conductivity of the cathode material and its electrochemical performance are further increased by metal ion(Al³⁺)doping.（1）The flower-like V₆O₁₃ microspheres assembled by ultrathin nanosheets were successfully synthesized by a simple hydrothermal synthesis method,in which the morphology was adapted via modification of nitric acid concentration（0、0.6、1.2、1.8、2.4和3.0 m L）.The results revealed that the flower-like V₆O₁₃ microsphere electrode material achieved a first discharge specific capacity of 368.1 m Ah/g（current density of 0.1 A/g）,with a remaining capacity of 313.1 m Ah/g after 50 charge/di scharge cycles.Even at a current density of 1 A/g,the electrode presented a first discharge specific capacity of 216.7 m Ah/g at a high current density（1 A/g）with the capacity retention rate of 81.3%after 200 cycles.（2）Hydrothermal method was performed to successfully synthesize flower-like VO₂（B）microspheres assembled by ultrathin nanosheets.Furthermore,the influence of oxalic acid concentration（0.252、0.504、0.756和1.008 g）on the morphology as well as the physical phase of VO₂（B）was studied by modifying its concentration.As the results showed,the flower-like VO₂（B）microsphere electrode exhibited a first discharge specific capacity of 282.9 m Ah/g with a capacity retention of 80.7%at a current density of 0.1 A/g（50 cycles）.Additionally,the electrode showcased a first discharge specific capacity of 216.7 m Ah/g at high current density（1A/g）as well as a capacity retention rate of 70.1%after 200 cycles.（3）Metal ions(Al³⁺)doping was performed on V₆O₁₃ and VO₂（B）with three-dimensional micro-nano structures to enhance their initial specific capacity and cycling performance further.For V₆O₁₃,the results showed that the A3(Al_0.05V_5.95O₁₃)ample had a high original discharge specific capacity of 385.1 m Ah/g at a current density of0.1 A/g with a cycle retention rate of 94.8%.It demonstrated an initial discharge specific capacity of up to 264.1 m Ah/g with a current density of 1 A/g.In the same way,as for VO₂（B）,AV3(Al_0.06V_0.94O₂（B）)sample exhibited a first discharge specific capacity of314.8 m Ah/g at a current density of 0.1 A/g（282.9 m Ah/g for AV0 sample）.Besides,it also displayed a high first discharge specific capacity of 229.2 m Ah/g at high current density（1 A/g）,and the capacity retention rate after 120 charge/discharge cycles（90%）was much higher than that of the AV0 sample（81.9%）.