Preparation And Application Of MOF/Carbon Composite Nanofibers In Lithium Sulfur Battery

Lithium-sulfur battery is regarded as a potential electrochemical energy storage with the advantages of low cost,high theoretical energy densityand friendly environment.However,lots of intrinsic hindrances,such as fast capacity degradation and migration of dissolved polysulfide intermediates,remain a significant challenge prior to the practical applications.Recently,many technologies have been developed to improve the performance of Li-S batteries.Among them,more attention has been paid to add a special interlayer in Li-S batteries to improve the electrochemical performance,which could not only improve the electron conduction rate,but also effectively capture the polysulfide and inhibit the shuttle effect.Among the functional materials for modifying the interlayer,metal organic framework-derived carbon material is considered as a promising material because of its large surface area,and its open metal sites can interact with lithium polysulfides,which considered to be a promising modified material.In view of the circulation stability of lithium sulfur battery due to shuttle effect of polysulfide in the circulation,this paper prepared ZIF/CNFs composite fiber,which was used as the middle layer of lithium sulfur battery.The ZIF/CNFs composite fiber used carbon fiber prepared by electrospinning method as the skeleton,with the ZIF-67 loaded on the surface of the fiber by different methods.The optimal structure was determined by the electrochemical performance of the battery with interlayer,which were obtained by different load method.Owing to the good electronic conductivity,the battery with ZIF/CNFs interlayer has a low battery impedance,and the interlayer could restrain the movement of polysulfide as a physical barrier.In addition,a series of gradient concentration of ligand solution was proposed to explore how ligand concentration influence the the morphology,phase composition and electrochemical performance of the composite fiber on the basis of the above research,and the optimal preparation process was determined.What’s more,the battery with ZIF/CNFs interlayer could perform a stable charge-discharge cycle at a high sulfur surface density.The result shows it can maintain a higher capacity cycle even under the sulfur surface density reached 3.2 mg/cm2.On the one hand,the ZIF/CNFs composite fiber act as a physical barrier to prevent the movement of polysulfide;On the other hand,it can interact with polysulfides,so that inhibit the shuttle effect of the polysulfide,and improve the performance of lithium sulfur battery.