| Energy storage and conversion in an efficient manner is of great significance for creating a zero-carbon emission world.At present,the dominant energy storage and conversion systems are lithium ion batteries(LIBs),which almost have occupied the portable electronic market owning to their light weight,high energy and long life.Nonetheless,the large-scale application of LIBs in the fields of electric vehicles and energy storage power stations will bring about more concerns about the cost and abundance of lithium resources.Under this background,sodium ion batteries(SIBs)are considered as promising candidates to replace LIBs because of the similar electrochemical properties of sodium and lithium,the much higher abundance of Na element on the earth as well as lower price of Na-related materials as compared to the Li counterparts.Among many anode materials for SIBs,antimony(Sb)based material is promising for its high theoretical capacity,low cost and stable charging and discharging platform.However,the antimony-based anode is suffering a huge volume change in the process of sodiation/desodiation,resulting in poor cycling stability,poor conductivity and the rate performance.In view of these problems,this paper focuses on the design of micro-nano structure of materials,combining some other methods such as element doping,carbon composite and heterogeneous synergy to improve the cycling and rate performance.The specific work is as follows:1)By simple hydrothermal method,uniform zinc sulfide nanospheres were first prepared as template precursor,and then Sb2S3 with hollow and yolk-shell structures were obtained by ion exchange and the control of feeding ratio.On this basis,the materials were coated with dopamine and calcined in the argon hydrogen environment,which not only improved the crystallinity of Sb2S3,but also formed an N-doped carbon layer outside the material to further improve the conductivity.Finally,Sb2S3@C with hollow and yolk-shell structure were obtained respectively.By comparing the sodium storage properties of the two structures of Sb2S3@C,the Sb2S3@C with yolk-shell structure shows obvious advantages in cycling and rate performance.In order to explore the cause of the difference,the two materials were characterized by contrast.XRD,XPS,Raman and BET tests showed no significant difference.Hollow structure of Sb2S3@C with was observed broken after 100 cycles by SEM and TEM,while yolk-shell structure of Sb2S3@C remained intact.EIS and GITT results showed that yolk-shell structure of Sb2S3@C had better kinetic reaction.Therefore,the better performance of Sb2S3@C with yolk-shell structure comes from the characteristics of the structure itself.2)An in-situ synthesis method of Sb1.24Bi0.76S3 nanorods was designed.According to the previous work,PDA was further coated and calcined to obtain Sb1.24Bi0.76S3@C.Sb1.24Bi0.76S3@C showed superior cyclic stability compared with Sb2S3@C and Bi2S3@C prepared by the same method.After 100 cycles at 0.2 A g-1,Sb1.24Bi0.76S3@C nanorods preserve the reversible capacity of 449.1 mAh g-1,in sharp contrast to the low capacity of Sb2S3@C and Bi2S3@C at the same current rate(215.1 mAh g-1 and 160.67 mAh g-1).At the ultra-high current density of 20 A g-1,Sb1.24Bi0.76S3@C retains a capacity of 550.9 mAh g-1,Sb2S3@C 394.7 mAh g-1 and Bi2S3@C 352.0 mAh g-1,respectively.3)Antimony with folded layered structure can also form single-layer or few-layer structure similar to graphene through various methods,called antimonene.The application of antimonene to sodium storage is also an effective method to deal with volume change.However,the existing methods of stably preparing antimonene have high requirements on experimental conditions and equipments.This chapter aims to explore the method of low-cost preparation of antimonene.Liquid phase method,ultrasonic exfoliation and electrochemical exfoliation were carried out.Different degrees of harvest were obtained,but the yield was very low,which became the priority problem to be solved. |
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