Preparation Of Selenium-based Anode Materials By Arc Discharge And Study On Sodium-storage Properties

In recent years,the application of electrochemical secondary batteries with the advantages of high energy conversion efficiency and simple maintenance has become an important way to solve the problems of fossil fuel depletion and environmental pollution.Among them,lithium-ion batteries（LIBs）have achieved great success.However,due to limited reserves and high cost of LIBs,developing new supplementary/alternative energy storage system is under urgent demand.Sodium-ion batteries（SIBs）with low cost have been regarded as one of the most promising candidate energy storage technologies in the future,but the development of high-performance anode materials is still a key challenge in the research of SIBs.Recently,selenium-based anode materials have become a new research star in this field because of their rich natural resources and high theoretical specific capacity.It is worth noting that selenium-based anode materials of SIBs still face some challenges that needed to be overcome,such as the volume expansion effect in the process of charge and discharge,inherent poor electrical conductivities of partial selenide and so on.In order to solve these problems,metal selenides with high specific capacity can be compounded with high conductive carbon to form nanomaterials.Arc discharge technology has the excellent characteristics of high reactivity,high dispersion and high efficiency in the synthesis of carbon-coated metal nanomaterials.Therefore,based on the preparation of selenium-based anode materials by arc discharge method,this paper explores the inhibitory effect of nanostructure design and carbon composite modification on the adverse volume expansion effect in the process of charge and discharge.The specific research work is as follows:（1）Highly dispersed spherical Sb₂Se₃/C nanoparticles with a diameter of about48 nm were controllably prepared.The nanometer size effectively can shorten the ion transmission path in the electrochemical reaction process.And the carbonaceous matrix can alleviate the drastic volume change in conversion and alloy reaction to a certain extent,and also acts as a conductive network to accelerate electron transfer.For this reason,Sb₂Se₃/C anode exhibits good cycling stability with a specific discharge capacity of 312.7 m Ah/g after 1290 cycles at 1 A/g.（2）SnSe/C nanocomposites with core-shell structure were successfully prepared in one step.SnSe has strong interface interaction with carbon shell.On the one hand,it is conducive to inhibit the agglomeration and deactivation of nanoparticles during cycling.On the other hand,the active material can be anchored on the carbon matrix through Sn-C chemical bond to improve the cycling performance of the anode.Therefore,SnSe/C anode shows good electrochemical reaction kinetics and ultra-long cycle life.At a current density of 2 A/g,its capacity can remain 237.8 m Ah/g after4220 cycles.（3）High purity mixed valence Cu_2-xSe/C nanocomposites were synthesized successfully by arc discharge reaction.Cu_2-xSe nanoparticles are dispersed and wrapped by carbon materials in the form of cross-linked skeleton.The local pea-pod structure is not only conducive to reduce the interface resistance between particles,but also effectively buffers the stress generated during sodiation and desodiation.For this reason,Cu_2-xSe/C anode shows excellent cycling stability and rate capabilities.It can deliver a specific discharge capacity of 237.8 m Ah/g after 1155 cycles at 2 A/g,and the capacity retention rate is as high as 98.4%.With the increase of current density from 0.1 A/g to 4 A/g,the capacity attenuation rate is only 15%.In addition,the full cell(Cu_2-xSe/C//Na₃V₂（PO₄）₃/C)also displays good cycling performance.The specific discharge capacity after 300 cycles is 238.5 m Ah/g at 0.3 A/g,which is close to the capacity of Cu_2-xSe/C half cell.In conclusion,based on the distinguishing feature of arc discharge method（simplicity,economy and fast speed）,this work provides an effective strategy for the preparation of high-performance SIBs anode materials,and enriches the research system of selenium-based anode materials for SIBs,which is conducive to accelerating the commercialization process of SIBs.