Study On Porous Carbon Matrix Composites Constructed By Sodium Chloride Template And Their Magnesium Storage Properties

Nowadays,sustainable energy has become the strategic goal of energy development.In the context of achieving carbon peak and carbon neutrality,it is the key to solve the problem of energy consumption and regeneration first.Magnesium battery has made some achievements in recent years,but it is still in the initial stage of development.The key problem in the development of magnesium sulfide battery is to achieve reversible deposition and embedding of magnesium,so it is necessary to develop a kind of electrode material with abundant morphology to limit the loss of sulfur elements.On this basis,some porous carbon matrix composites with abundant holes were designed in this paper,which were then vulcanized and used as positive electrode materials for MIB.Based on the hierarchical pore making strategy,the reversible transport of magnesium ions was promoted by using the characteristics of various materials.For example,the high energy storage property of carbon nanotubes was used to improve the long cycle performance of materials.The special structure of the heterojunction was used to promote the electrochemical reaction between magnesium and sulfur.Electrochemical properties and magnesium storage mechanism of the materials were explored through various characterization techniques and electrochemical tests.Specific research contents were as follows:（1）Porous carbon materials were prepared by the method of hierarchical pore-making,and the S@C composite material formed after loading sulfur was used as the positive electrode material of magnesium ion battery.By combining hydroxyethyl cellulose gel with sodium chloride template method,porous carbon materials with controllable morphology were obtained by freeze-drying carbonization and other means,and S@C composite material was synthesized as battery cathode material after loading high proportion of sulfur（80 wt%）.Magnesium ion batteries based on S@C composite materials have excellent electrochemical performance,in addition to the interconnected holes,the electrode material has abundant electron and ion transport channels.The hollow structure of the carbon material contributes to the contact electrode-electrolyte contact area,ensuring a high current ion supply.The S@C composite showed excellent magnification performance,and 242 m Ah g^-1 was still available when the current density was 2000 m A g^-1.The reaction mechanism of S@C material with magnesium ion was expressed through the analysis of its electrochemical performance.（2）In S@C composites,on the basis of using acrylamide polymerization of functional groups,makes the hydroxylation of carbon nanotubes and hydroxyethyl cellulose formed the combination of good and generate complex porous structure,negative after sulfur S@C/CNT can be used as store up magnesium materials.Through the observation of its morphology,it can be seen that the carbon nanotubes are evenly distributed near the pores of porous carbon,which causes the disappearance of some pores,but the addition of carbon nanotubes increases the formation of small pores and enhances the energy storage characteristics of the material.In addition,by XPS analysis shows that sulfur in C/CNT material mainly exists in the form of short chains of sulfur,this reduces the dynamics in the process of material in charge,make S@C/CNT with S@C material in the same proportion of negative sulphur content,has more excellent electrochemical performance.It shows good cycling performance and can maintain about 80%discharge capacity after 100 cycles.（3）Heterogeneous structure can promote mass and electron transfer.On the basis of C/CNT material,Mo element is introduced by soaking method,and then the composite with Mo O₂and Mo O₂/Na_0.88Mo₆O₁₇ heterojunction is prepared by sintering.Then,after vulcanization,S@C/CNT@Mo O₂/Na_0.88Mo₆O₁₇ was obtained as the positive electrode material of magnesium battery.Compared with the magnesium ion battery based on S@C/CNT,the magnesium ion battery based on S@C/CNT@Mo O₂/Na_0.88Mo₆O₁₇inherits the long cycle stability of S@C/CNT material.Through the long cycle test,it can be seen that its stability is more excellent,under the current density of 200 m A g^-1,300 cycles after the discharge capacity of 90 m Ah g^-1,so there is still a great potential for development.