Study On Electrospinning Preparation And Sodium Storage Properties Of Tin-based Sulfide Composite Anode Materials

Tin-based sulfide（SnS₂ and SnS）,with the merit of high theoretical specific capacity based on conversion and alloying reactions,have been considered as promising anode materials for sodium ion batteries（SIBs）.However,terrible volume change caused by Na-Sn alloying reactions lead to poor electrochemical performance of bare tin-based sulfide,and thus they are greatly restricted in practical applications.Therefore,effective measure must be taken to minimize the volume effect and improve the sodium storage performance of tin-based sulfide.In this dissertation,in an attempt to improve the electrochemical performance of tin-based sulfide,the SnS₂/C and SnS/C nanofibers were synthesized by a facile electrospinning method and subsequent calcination.A series of physical characterization and the sodium storage performance of SnS₂/C and SnS/C nanofibers have also been studied systematically.The main works are as follows:SnS₂/C nanofibers were prepared via electrospinning.In the calcination process,the vacuum calcination is utilized skillfully,and the sulfuration of the raw material SnCl₄,the carbonization of PVP,and the N,S dual-doping of carbon are realized in one step.When the SnS₂/N,S dual-doped carbon（SnS₂/NSDC）nanofibers are used as an anode material for the sodium ion battery,excellent sodium ion half-cell performance and full-cell performance are achieved.In Na half-cell,the SnS₂/NSDC nanofibers show long cycle life and excellent rate capability.When a current density of 200 mA/g was applied,after 200 cycles,the capacity of SnS₂/NSDC nanofibers retains at 380.1 mAh/g.More importantly,the SnS₂/NSDC nanofibers also show high capacity of 310.6 mAh/g when cycling at an ultra-high current density of 4000 mA/g.In Na ion full-cell,the full-cell also exhibited a high initial discharge specific capacity of 349.8 mAh/g with an initial coulombic efficiency of 96.8%.Moreover,the energy output of full-cell is sufficient to lights 24 LEDs（2V）.The excellent electrochemical performance suggests the availability of the SnS₂/NSDC nanofibers in practical applications.Except for SnS₂,SnS is also a promising anode material for sodium-ion battery.Thus,flexible SnS/C nanofibers（SnS/C NFs）film were prepared by electrospinning technology followed by calcination.When the SnS/C NFs film directly used as a free-standing anode in the SIBs without using metal current collector,conductive additive and binder,excellent sodium storage performance were obtained.The SnS/C NFs electrode can deliver a high capacity of 481 mAh/g at 50 mA/g after 100 cycles.Not only that,the SnS/C NFs electrode also showed ultra-long cycle life for 500cycles.The sodium cell was disassembled after 100 cycles,it was surprised found that the SnS/C nanofiber electrode still maintained its structural integrity,and the fiber morphology of the SnS/C nanofiber has hardly changed.These are the main reasons why the SnS/C nanofiber electrode has an ultra-long cycle life.