Preparation And Zinc Storage Performance Of Vanadium Sulfides Nanostructured Electrode Materials

Zinc ion energy storage equipment is considered to be a promising candidate product for the next generation energy storage system due to its high safety,resource availability and environmental friendliness.However,the instability of zinc metal anode hinders the practical applicability of zinc-based alloys.Specifically,the formation of dendrites on the zinc surface and the hydrogen evolution reaction seriously affect the coulombic efficiency and cycle stability of zinc-based alloys.In recent years,more and more efforts have been devoted to overcoming these obstacles through electrode structure design,interface modification and electrolyte/diaphragm optimization.However,these studies are based on the traditional understanding of electrochemical metal plating,and factors such as current density,peeling and/or deposition capacity,and distance between electrodes are not taken into consideration.Therefore,the key to the development of zinc ion energy storage devices is to design and develop new and efficient materials to replace zinc metal anodes.In this thesis,it is successful to prepare a three-dimensional vanadium tetrasulfide/graphene(3D-VG)composite material with a one-step hydrothermal method,VS₄ nanosheets are uniformly grown in a three-dimensional conductive graphene network structure.VS₄ is a chain structure molecule coordinated by V⁴⁺ions and two sulfur dimers(S₂^2–),and each atomic chain is bonded through weak van der Waals forces to provide a loose stack structure.The spacing between the atomic chains of VS₄ is 5.6(?),which is much larger than the ion diameter of Zn²⁺(0.74(?)).The open channels between the atomic chains of VS₄ will provide abundant active sites for Zn²⁺diffusion and storage.The three-dimensional graphene grid frame in the composite can avoid the agglomeration of VS₄ nanosheets to maintain structural stability and enhance electrical conductivity.To explore the superiority of the conductive 3D hierarchical graphene framework in the 3D-VG hybrid,two contrast samples of VS₄ and VS₄+r GO were introduced into these electrochemical tests.the VS₄ sample was prepared as 3D-VG with the same process excepting the addition of GO,and r GO was synthesized without NH₄VO₃ and TAA.The VS₄+r GO sample is the physical mixture of VS₄ and r GO with the same proportion of ingredients of 3D-VG.By studying the relationship between its microstructure and performance,we assembling it as an electrode material for Zn-Ion Batteries(ZIB)and have a series of electrochemical tests.The results show that the 3D-VG negative electrode exhibits significant Zn²⁺ion storage performance,maintains a high reversible capacity at high rates,and exhibits excellent stability over long cycles.A very high specific capacity of643 m A h g^-1 is obtained for the 3D-VG anode delivered at 0.1 A g^-1,it remains a specific discharge capacity of up to 470 m Ah g^–1 at a current density of 1 A g^–1 with a capacity retention rate of 99%after 100 cycles.we assemble an aqueous Zinc ion Hybrid Supercapacitors(ZHC)using 3D-VG as an anode and mesoporous AC(MAC)as a cathode.the ZHC exhibits excellent gravimetric specific capacitance of 499.4 F g-₁ at the scan rate of 0.1 m V s^-1and still achieves 220.0 F g^-1 at 1 m V s^-1,Cycling stability at a high current density of 10A g^-1 is presented during the GCD process,the coulombic efficiency of the device is always close to?100%over 10000 cycles,after10,000 cycles,it can have a high capacity retention rate of 88%compared to its initial value.