Preparation Of Multifunctional Interlayer And Its Application In Lithium-Sulfur Batteries

The topic of energy is an unavoidable hotspot for human society all the time.With the development of science and technology,accompanied by the environmental protection concept’s popularity,the new energy storage system has become a promising resource to replace traditional non-renewable and widen the horizontal for the future energy supply.Nowadays,new energy vehicles and electronic devices based on lithium batteries have entered the lives of the masses.However,technological exploration never stops,and researchers make effort to explore the possibility of other energy storage systems to replace.Lithium-sulfur battery（Li-S）,as a branch of lithium battery,is concerned by researchers with its high theoretical specific capacity.Nevertheless,the low conductivity of sulfur and its discharge products of Li-S,and the shuttle of the soluble intermediate products between the anode and cathode limit the commercial application of lithium-sulfur battery.In view of the inherent defects of Li-S,we prepared three different multi-functional interlayers intervened on the cathode side,which were based on three aspects of physical limitation,chemical adsorption and chemical catalysis.The specific work is as follows:（1）Through electrospinning and carbon treatment techniques,we successfully fabricated cross-linked carbon nanofibers acted as a three-dimensional conductive network,which supplied abundant electron transport channels for the redox process.ZIF-8 crystals were introduced by in-situ growth on the carbon skeleton（ZCS）.As a common used MOFs-type material,ZIF-8 can adsorb polysulfide through Lewis acid-base interaction to limit its shuttle.ZCS-based lithium sulfur batteries showed a low decay rate per cycle of 0.07%after 300 cycling at 1C.（2）The germanium（Ge）doped nitrogen（N）-rich carbon skeleton（GNCS）interlayer was prepared by simple electrospinning and carbonization,which was applied to lithium sulfur battery.N-rich carbon skeleton not only could restrict the polysulfides via physical limitation,but also worked as the second current collector that speed electronic transmission.Additionally,metal germanium nanoparticles on the carbon skeleton can be used as chemical adsorbent anchor the shuttle polysulfides,meanwhile,which were served as catalyst sites to accelerate the transformation of polysulfides.The experimental results show that the insertion of GNCS interlayer improves the electrochemical kinetics,and achieves better electrochemical performance of Li-S.As displayed,GNCS-based lithium sulfur batteries showed a decent long-cycling performance of 755.6 m Ah g^-1 after 300 cycling at 1C.（3）Through a simple fabrication process,carbon nanofibers modified with metallic Sb nanoparticles（SCNF）were successfully constructed and reacted as an independent interlayer of Li-S.The existences of SCNF as a multi-functional interlayer integrating many functions,which can effectively ameliorate the problems existing in lithium sulfur batteries.Specifically,the carbon nanofibers show a network structure that can serve as a conductive framework and provide sufficient ion channels.In addition,the metallic Sb nanoparticles as adsorbent and catalyst for polysulfides capture and conversion,availably relieve the shuttle effect,and thus reduce the capacity loss caused.The battery with SCNF interlayer exhibited an initial specific capacity of 939.1 m Ah g^-1 at 1 C,and the capacity decay rate was 0.06%after 800cycles.