Hydrothermal Synthesis And Intercalation Of V-based Materials For Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries（ZIBs）are an emerging type of battery.It uses zinc metal as the negative electrode,so the price is inexpensive.And the use of aqueous electrolyte also ensures higher safety characteristics of aqueous ZIBs,which means the lower assembly requirements for energy storage devices.When vanadium is used as a cathode material,the conversion of its multivalent state realizes the transfer of multiple electrons,which makes the V-based material have a higher theoretical specific capacity.In this paper,V₂O₅ and NH₄VO₃were used as raw materials to synthesize cathode materials applied for aqueous zinc ion batteries through structural optimization and adjustment,ions or organic compound intercalating.XRD,FTIR,Raman,SEM and other characterization methods were adopted to test the morphology and structure of the prepared sample.CV,GCD and other testing methods were mainly adopted to analyze the zinc storage performance,which proved the structural adjustment and intercalation way improving the energy storage effect and charge transfer efficiency of V-based materials as electrode materials.The main contents are as follow:（1）Using NH₄VO₃ as the raw material,（NH₄）₂V₆O₁₆ was synthesized by a one-step hydrothermal synthesis method after exploring and adjusting the synthesis conditions,which was used as the electrode material for the aqueous ZIBs.According to the CV test results,（NH₄）₂V₆O₁₆ has good electrochemical cycling stability in the voltage range of 0.3-1.7 V.GCD results show that the specific capacity of（NH₄）₂V₆O₁₆ electrode can reach up to a maximum value of 323.5 m Ah·g^-1 at a current density of 0.1 A·g^-1.At a current density of 5 A·g^-1,the maximum specific capacity of（NH₄）₂V₆O₁₆ can reach up to 238.7 m Ah·g^-1,and the specific capacity still keeps 78%remained after 2000 cycles.At the same time,（NH₄）₂V₆O₁₆ has good rate performance.It also can get an energy density of 249 Wh·kg^-1 at 99 W·kg^-1.（2）In order to achieve the purpose of improving the electrochemical performance,we took advantage of the layered characteristics of the vanadium oxide layers to design a non-metallic cation intercalation method controlling the layered structure of the hydrated vanadium pentoxide（V₂O₅·n H₂O）.NH₄⁺intercalated hydrated vanadium pentoxide flexible nanoribbons were successfully synthesized by the hydrothermal synthesis method,abbreviated as NVOH.The interlayer spacing of NVOH was measured to be 11.2?through various characterization methods.As a positive electrode material of ZIBs,CV test proved that it had good cycling stability in the voltage range of 0.3-1.6 V.At a current density of 0.1 A·g^-1,the discharge specific capacity of NVOH can reach up to a maximum value of 372 m Ah·g^-1.At a current density of 5 A·g^-1,GCD result shows that the discharge specific capacity is still 175 m Ah·g^-1after 2000 cycles.At the same time,NVOH also has good rate performance and excellent power density and energy density.At a power density of 155 W·kg^-1,it has an energy density of 273Wh·kg^-1.（3）In order to improve electrochemical performance through the synergistic effect of the conductive polymer and the vanadium oxide layers,we designed an interface intercalation method to introduce polyaniline（PANI）between the V₂O₅·n H₂O layers.It has been confirmed that PANI was successfully intercalated into the V₂O₅·n H₂O by XRD,FTIR,Raman and other characterization methods,abbreviated as PANI-VOH.The vanadium oxide layer spacing of PANI-VOH was measured to be 14.1?.In the electrochemical tests,PANI-VOH shows excellent rate performance.At a current density of 0.1 A·g^-1,PANI-VOH can reach up to a maximum specific capacity of 363 m Ah·g^-1.The discharge capacity of PANI-VOH can reach up to be 270 m Ah·g^-1 at a current density of 5 A·g^-1,and the capacity still keep 86%remained of initial capacity after 2000 cycles.Through calculation and analysis,the energy density of PANI-VOH can reach up to be 275 Wh·kg^-1 at 78 W·kg^-1.