Research On The Controllable Synthesis And Performance Of Vanadium-based Supercapacitor Electrode Materials

Supercapacitor,as a new type of energy storage device,has been widely used in many fields because of its fast charging and discharging speed,long cycle life and high power density.The most important factor affecting the performance of supercapacitors is the selection of the electrode material.Among them,the vanadium based materials have the characteristics of simple synthesis,low cost and higher theoretical capacitance,which are widely used as electrode materials for supercapacitors.In this paper,from low to high according to the valence of vanadium,we have successfully prepared a series of vanadium based supercapacitor electrode materiasl.The specific work of this article is mainly carried out from the following five aspects:1.Facile synthesis of VIV-MOFs for high performance supercapacitorsIn order to prepare VIV-MOFs(VIVO(bdc),bdc=1,4-terephthalic acid)from the preparation of the most common Ni-MOFs with six hydrated nickel nitrate and terephthalic acid as raw material,through a solvothermal method to prepare a new type of accordion like Ni-MOFs,and it is used as electrode material supercapacitor.By improving the method of preparing Ni-MOFs,then a rod like VIV-MOFs supercapacitor electrode material was synthesized by solvothermal method with vanadium sulfate and terephthalic acid as raw material.The specific surface area of the electrode is 116.8 m2 g-1.Under the test conditions of three-electrode system,the specific capacitance of the rod like V-MOFs is 520.8 F g"1 at the current density of 1 A g-1,and it has excellent cycling stability.Subsequently,the rod like V-MOFs were used as cathode material and activated carbon as negative electrode material.Water and solid state asymmetric supercapacitors were constructed respectively.It was found that both of them had excellent superconducting properties both in water system and solid state.The research on the synthesis of rod like VIV-MOFs and the performance of supercapacitor provides a reference for the development of MOFs based electrode materials for high pexformance supercapacitor.2.Facile synthesis of CUV2O5 nanobelts for supercapacitorsThe Cu superstructure was synthesized by one step hydrothermal method using the leaves of Magnolia and copper sulfate as the starting material.Then the CUV2O5 nanobelts were prepared by hydrothermal reaction with the Cu superstructure,V2O5 and hydrogen peroxide,and then the CuV2O5 nanobelts were used as electrode materials for supercapacitors.In the test conditions of the three-electrode system,at a current density of 1 A g-1,the specific capacitance can reach 701.3 F g-1;After 10000 cycles,the capacitance retention rate was 91.2%.In the asymmetric supercapacitor conditions(CUV2O5 nanobelts and activated carbon were used as cathode and anode materials,respectively),When the power density is 86.4 W kg-1,the energy density of the supercapacitor is 34.8 Wh kg-1.When the power density increases to 1515.3 W kg-1,the energy density of the supercapacitor can still reach 24.8 Wh kg-1.3.Facile synthesis of amorphous AIV3O9 microspheres for supercapacitorsUsing polyvinylpyrrolidone(PVP)as a surface active agent and a soft template,the amorphous AIV3O9 microspheres were synthesized by a simple one step hydrothermal method.The amorphous AIV3O9 microspheres used as electrode material for supercapacitor exhibited super excellent electrical properties,including the high specific capacitance(at a current density of 1 A g-1 the amorphous AIV3O9 microspheres show the capacitance of 545 F g-1)and excellent cycle stability(at a current density 1 A g-1,after 10000 cycles,the capacitance loss is only 11%).Furthermore,the amorphous AIV3O9 microspheres positive electrodes and the active carbon as negative electrode were assembled into the asymmetric supercapacitor.The energy density of the asymmetric supercapacitor could reach 37.2 Wh kg-1 when the power density was 1124.4 W kg-1.4.Facile synthesis of 3D belt-like AIV3O9 for supercapacitorsHexadecyl trimethyl ammonium bromide(CTAB)was used as surfactant and soft template to synthesize 3D belt-like AIV3O9 via simple hydrothermal method.The prepared AIV3O9 has three dimensional belt-like porous structure,which is an ideal electrode material for supercapacitor.Under the test condition of three-electrode system,the specific capacitance can reach 521 F g-1 at the current density of 1 A g-1,and its capacitance retention is 91.5%after experiencing 10000 charge-discharge cycles.The 3D belt-like AIV3O9 cathode and activated carbon cathode assembly of asymmetric capacitor,the supercapacitor showed a long cycle life(after 10000 cycles,the capacitance loss is only 7.4%).5.Facile synthesis of flower-like Co3V2O8 for supercapacitorUsing acetylacetone cobalt,ammonium metavanadate and tetrabutylammonium bromide as raw material,through a simple solvothermal method,we successfully prepared flower-like Co3V2O8.When the current density is 1 A g-1,the specific capacitance of the electrode material can reach 773.1 F g-1.Window voltage of the asymmetric supercapacitor that composed of flower like structure of Co3V2O8 cathode and active carbon negative electrode in aqueous solution is 1.6 V.When the current density is 1 A g-1.after 10000 cycles,the asymmetric supercapacitor can maintain 93.2%of its initial specific capacitance.When the power density is 400.2 W kg-1,the maximum energy density can reach 41.8 Wh kg-1.