Study For Sodium Storage Of Multi-Scale Structure Sb₂S₃/CoS₂ Nanofiber Materials

Energy storage technologies,represented by secondary batteries,have been widely acknowledged due to their portability,high energy density,and fast response capabilities.Among them,sodium-ion batteries（SIBs）possess unique cost advantages over lithium-ion batteries（LIBs）due to the extreme abundance of sodium.Since electrode materials are crucial components influencing their performance,Antimony sulfide is a highly promising antimony-based alloy material for the anode electrode of sodium-ion batteries,with a high theoretical capacity..However,the practical application of antimony-based materials has been severely hindered by the significant volume change,low electrical conductivity,and sluggish diffusion kinetics during the alloying process.Therefore,in order to improve the cycle and rate performance of antimony-based materials in sodium ion batteries,the design of two components and the construction of heterogeneous hollow nanofibers are taken as the starting point,the main research work is as follows:（1）The Sb₂S₃/CoS₂ composite nanofibers were prepared using electrospinning and heat treatment techniques,and were further characterized for their morphology,crystal structure,and electrochemical performance.The results indicate that compared to single-component electrodes,the Sb₂S₃/CoS₂ composite electrode material exhibits superior cycling performance.The reversible capacity of the dual-component Sb₂S₃/CoS₂electrode material was 353.2 m Ah g^-1 under current density of 3 A g^-1 for 100 cycles,while that of the pure Sb₂S₃ and CoS₂ electrode materials were 177.7 m Ah g^-1 and 45.1m Ah g^-1 respectively.This is due to the synergistic effect between Sb₂S₃ and CoS₂,which is beneficial to improve the cycle stability of sodium ion batteries.（2）Based on research conducted on dual-component composites,further enhancements are sought in the rate performance and cycling stability of the composite materials under high current densities.The rational design of the composite fiber structure is based on the advantages provided by multiple scales.In this study,Sb₂S₃,which exhibits a larger volume change,is selected as the core material for the core-shell nanofibers,while CoS₂ is chosen as the main component for the shell design.The core-shell structure not only greatly mitigates the volume expansion of the electrode material during the charge-discharge process,but also provides more active sites for redox reactions.The Sb₂S₃@CoS₂ hollow nanofiber with a core-shell structure exhibited excellent rate performance(reversible capacity of 825 m Ah g^-1 when the current density is restored to 0.2 A g^-1)and splendid cyclic stability(under a high current density of 10 A g^-1,2400 cycles,reversible capacity of 320 m Ah g^-1)when used as anode electrode material for sodium-ion batteries.In addition,the phase change of the Sb₂S₃@CoS₂hollow nanofiber electrode material during charge and discharge process was studied by in-situ XRD technology.Characterization results showed that the main mechanisms of sodium storage for Sb₂S₃ in the hollow nanofibers with core-shell structure are conversion and alloying processes,whereas CoS₂ exhibited intercalation and conversion reactions.The coupling effect of these two components greatly improved the cycling and rate performance.