Modified Vanadium Metal Oxide As Cathode Material For Lithium Sulfur Battery And Its Electrochemical Performance Analysis

With the rapid development of modern science and technology,mankind's demand for green environmental protection and clean energy is increasingly urgent,and the battery field has gradually become a focus of human attention.In recent years,lithium-sulfur batteries have become the research focus of researchers in various countries due to their own theoretical specific capacity,low cost of active materials,and high safety performance.However,due to its own shortcomings such as low conductivity,volume expansion and shuttle effect,the discharge performance and cycle performance of the battery are affected.Modification of the cathode material has become an important means to optimize battery performance.This article mainly explores the preparation and performance analysis of modified vanadium metal oxides as cathode materials for lithium-sulfur batteries.First,commercial V₂O₅ and S are uniformly mixed according to different mass ratios by high-temperature sintering under an argon atmosphere,and after being fully calcined,they are coated on the surface of aluminum foil to make a composite electrode material.The experimental results show that although the material particles have obvious agglomeration,they still have a large specific surface area and porosity.When the mass ratio of commercial V₂O₅ to S is 9:1 and the current density is 0.5 A/g,the specific capacity can reach 110.86 mAh/g.Secondly,in order to optimize the material structure and increase the S loading,a carbon-coated V₂O₅ matrix material was obtained using polyvinyl alcohol and sucrose as carbon sources,respectively.Carbon was coated with V₂O₅/S composite electrode material after S was compounded at different mass ratios by the hot-melt method.According to scanning electron microscope?SEM?,X-ray powder diffraction?XRD?,cyclic voltammetry?CV?,alternating current impedance?EIS?,charge and discharge tests,it can be seen that when polyvinyl alcohol is used as the carbon source,When the S mass ratio is 1:3,the discharge specific capacity can reach 590 mAh/g at a current density of 320 mA/g,and its discharge capacity still exceeds 400 mAh/g after 100 charge and discharge cycles.When sucrose is used as the carbon source and the carbon-coated V₂O₅ to S mass ratio is 1:4,the discharge specific capacity can reach 670 mAh/g at a current density of 320 mA/g.After 100 charge and discharge cycles,the discharge capacity still exceeded 400 mAh/g.The carbon-coated V₂O₅ matrix material prepared by the two carbon sources can significantly increase the load of S and has a more stable structure.Comparing the two carbon sources,after cycling 100 times at a current density of 320 mA/g,the capacity decay rate was 33.4%when polyvinyl alcohol was used as a carbon source,and the capacity decay rate was 38.8%when sucrose was used as a carbon source.In the preparation process of polyvinyl alcohol,the temperature required for calcination is lower,the volume change is small,the loss rate of the material is small,and it is more convenient for subsequent synthesis.Finally,nano-scale V₂O₅ was prepared by hydrothermal method.It was found that when the hydrothermal temperature was 140?,the overall material distribution was uniform and the electrochemical performance was the best.Based on this,polyvinyl alcohol was selected as the carbon source for carbon coating treatment,and then compounded with S at different mass ratios to obtain carbon-coated nano V₂O₅/S composite electrode materials.Through physical characterization and electrochemical performance tests,it was found that nano-scale V₂O₅ materials can effectively increase the sulfur load.Although the discharge capacity has slightly decreased,its cycle stability has been significantly improved.When the mass ratio of nano-scale V₂O₅ to polyvinyl alcohol is 1:1 and the mass ratio of carbon-coated material to S is 1:5,the best electrochemical performance is exhibited.The discharge capacity can reach 483 mAh/g at a current density of 340 mA/g,and the capacity is still 270 mAh/g after 150 cycles.