Preparation Of Vanadium Pentoxide Composite Materials And Research As Aqueous Zinc Ion Batteries Cathode Materials

Convenient energy storage devices are very important for human.Lithium-ion batteries are the mainstream mobile energy storage devices on the market because of their advantages such as high energy densities,good stability,and convenience.However,the lithium resources on the earth are extremely limited,which leads to the rising cost of lithium-ion batteries.And because lithium-ion batteries use organic electrolytes,they are extremely prone to combustion and explosion during use.Therefore,mankind urgently needs to find the next generation of energy storage equipment to replace lithium-ion batteries.Aqueous zinc-ion batteries have the advantages of low cost and high safety factor.However,due to the large electrostatic effect and poor dynamic performance of Zn2+,it is urgent to find suitable cathode materialsThe transition metal oxide V2O5 has the advantages of large interlayer distance,simple preparation process,and low cost.After the C2H2O4·2H2O and commercial V2O5 were stirred and heated for calcination,nano-sheet V2O5 was successfully prepared,and it also showed outstanding electrochemical performance as a cathode material.However,V2O5 has poor conductivity as an electrode material.In order to solve the above problems,V2O5/C composite material was prepared by ball milling the nano-sheet V2O5 and carbon black,which effectively reduced the charge transfer resistance and improved the electronic conductivity.In addition,V2O5 is a layered oxide,and its layers are connected by weak van der Waals force,so the stability of V2O5 crystal structure is poor.Based on this situation,K+ions were inserted into the interlayer vacancies of V2O5 by hydrothermal synthesis,adjacent oxygen ions were connected by K-O chemical bonds to obtain a nanowire K0.5V2O5.Moreover,DFT simulation calculations confirmed that the K0.5V2O5 cathode material has a more stable crystal structure than V2O5.At the same time,K0.5V2O5 cathode also showed excellent electrochemical performance.At a current density of 2 A g-1,K0.5V2O5 discharge capacity was 268.7 mA h g-1 in the first cycle and its discharge capacity still remained at 167.1 mA h g-1 after 150 cycles Even under a current density of 5 A g-1,after 3000 cycles,its discharge capacity can be maintained at 140.3 mA h g-1,and its capacity retention rate is close to 75%.Compared with other similar potassium vanadate materials,K0.5V2O5 also exhibits satisfactory electrochemical performanceFurthermore,the electrolyte resistance of V2O5 is poor,and in 3M ZnSO4 electrolyte,a series of interface negative effects such as dissolution and side reactions easily occur.In order to solve the above problem,AlF3@V2O5 composite material was obtained by heating and stirring NH4F,Al(NO3)3,nanosheet V2O5,and then calcining.And through a series of characterization tests such as SEM,TEM,EDS,it was confirmed that AlF3 was uniformly coated on the V2O5 surface.And because AlF3 has stable chemical properties,AlF3@V2O5 can effectively inhibit dissolution and interface side reactions.Furthermore,AlF3@V2O5 was subjected to electrochemical cycling tests at a current density of 0.1 A g-1.It has an initial discharge capacity of up to 328.1 mA h g-1,and can still maintain discharge capacity of 140.5 mA h g-1 after 120 cycles.Finally,it is believed that with the improvement of various methods,V2O5 has a broader prospect in the field of cathode for aqueous zinc ion batteries.