Prepartion And Performance Analysis Of V₂C MXene Derived Vanadium Oxide Zinc Ion Battery Cathsde Materials

Aqueous zinc ion batteries are considered as a promising new energy storage system to replace lithium ion batteries because of their low cost,high safety,low environmental pollution and high reversible capacity.The lack of suitable embedded cathode materials is currently the main factor hindering the commercialization of aqueous zinc ion batteries,therefore,it is important to develop aqueous zinc ion battery cathode materials with high performance and good stability.This paper focuses on the synthetic design and mechanistic analysis of MV_xO_y-n H₂O type vanadium-based materials.In order to develop high performance aqueous zinc ion battery cathode materials,the experiments are divided into two stages:phase transition reaction and ion exchange reaction,firstly,the phase transition reaction of oxidation of two-dimensional material V₂C is induced by ammonium metavanadate using the valence neutralization process of element V,and then the exchange reaction of ammonium ion and sodium ion in vanadium oxide structure is realized by high concentration of Na⁺conditions using hydrothermal process The two-step hydrothermal synthesis method of HNa V₆O₁₆was constructed.By varying the conditions of the two-step hydrothermal synthesis,the products of the first and second steps were tested and analyzed,and the mechanism of the phase transition and ion exchange process could be studied more clearly.Firstly,the H⁺concentration conditions in the first step hydrothermal synthesis reaction were investigated,and the relationship between the product structure and electrochemical properties was analyzed in combination with FTIR and other characterization and electrochemical tests.The effect of hydrogen ion concentration on the degree of reaction of the phase transition process is very obvious.HNa V₆O₁₆with high structural regularity and purity was synthesized under the optimal hydrogen ion concentration conditions of 23m L 0.2 M dilute sulfuric acid,and the hydrogen sodium ions embedded in vanadium oxides gave the material good Zn²⁺transport kinetics and ion storage capacity.A reversible capacity of 393.2 m Ah g^-1at 0.1 A g^-1,57.4 m Ah g^-1when the current was increased to 12.0 A g^-1,and a capacity retention of 88.2%after 1000 cycles at 5 A g^-1were obtained.Then the sodium ion concentration conditions in the second hydrothermal reaction step were investigated,and the products were analyzed by morphological and electrochemical tests,and it was found that under the optimal sodium ion concentration conditions with the addition of anhydrous sodium sulfate at 8.0 g,the ammonium ions in the vanadium oxide structure could be removed better,and the HNa V₆O₁₆cathode material with the best electrochemical performance was successfully synthesized,and the material was a unique nanoribbon attached to the MXene nanosheet structure,the vanadium oxide layers embedded between the hydrogen sodium ions increase the layer spacing to provide more ion channels,combined with water molecules to enhance the stability of the structure and accelerate the rate of Zn²⁺transport.The excellent electrochemical properties and stability make the material promising for application.Finally,the V₂C/VO₃^-ratio conditions were explored to investigate their effects on the morphology and properties of the derived vanadium oxides,and HNa V₆O₁₆with high purity was successfully synthesized with the structure of a small number of nanoribbons uniformly attached to MXene nanosheets.Another sodium-ion-embedded vanadium-based anode material Na₂V₆O₁₆was synthesized at a mass ratio of V₂C and NH₄VO₃of 1:58.The electrochemical performance tests and characterization analyses such as XPS and FTIR were performed on the products of the two different structures,and the reversible capacity and long cycle life of HNa V₆O₁₆were better than those of Na₂V₆O₁₆at all current densities,and HNa V₆O₁₆at The reversible capacity of HNa V₆O₁₆is 414.1 m Ah g^-1at a current density of 0.5 A g^-1,and still 101.1 m Ah g^-1when the current density is increased to 20.0 A g^-1.The capacity retention rate is 80.1%after 7000 cycles at 20 A g^-1.The results indicate that when the mass ratio of V₂C and NH₄VO₃is increased to a certain degree,the vanadium oxide undergoes phase transformation and H⁺is This increases the space in the vanadium oxide layer,accelerates the Zn²⁺transport kinetics and storage capacity,and improves the multiplicity performance and cycling stability of the battery.