Design, Preparation And Electrochemical Performance Of Tin And Bismuth-based Anode Materials

Group ? A and Group ?A metals or their alloys can be used as anodes for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs).For example,Sn,Bi-based alloys have high theoretical capacity and are considered as ideal anodes for LIBs and SIBs.However,these alloy materials have large volume changes(about 300%)during the reaction,which easily cause the electrode material to be crushed and fall off from the electrode surface,resulting in poor electrochemical performance,which greatly limits their application In LIBs and SIBs.Therefore,we designed and synthesized a series of new tin and bismuth-based alloy materials to suppress the volume expansion of electrode materials during the reaction and improve electrochemical performance.In this paper,using liquid potassium sodium(KNa)alloy as reducing agent,tin and bismuth-based alloy nanoparticles were prepared rapidly at room temperature with the help of liquid phase shear assisted method.By the one-pot method,Sn and Bi based alloy and graphene composite materials were prepared as anode materials for LIBs.Two-dimensional bismuth nanosheets were synthesized using liquid potassium sodium alloy as template by low temperature solvothermal synthesis method.And the 2D Bi nanosheets/graphene hybrid was made as an anode material of SIBs.The specific research content is as follows:1.Tin/bismuth alloy nanoparticles@reduced graphene oxide(Sn Bi@RGO)hybrids were synthesized by one pot method using tin tetrachloride and triphenylbismuth as raw materials and graphene oxide as carrier.The composite electrode material was used as anode material of LIBs.Using liquid KNa alloy as reducing agent,this method can produce nano Sn Bi alloy particles at room temperature and prepare reduced graphene oxide(RGO)at the same time.Reduced graphene oxide becomes a good supporting frame,which can inhibit the volume expansion of Sn-Bi alloy electrode material during the charge and discharge process,which shows good cycle stability and rate performance.At 100 m Ag^-1current density,the first cycle has a discharge specific capacity of 689 m Ah g^-1,and after100 cycles,it still has a discharge specific capacity of 218 m Ah g^-1.2.Tin/cobalt alloy nanoparticles@reduced graphene oxide(Sn Co@RGO)hybrids were one pot synthesized by shear-assisted liquid phase reduction of KNa alloy process using tin tetrachloride and cobalt acetylacetonate as raw materials and graphene oxide as carrier.It was used as the anode material of LIBs.The reducibility of liquid alkali metal alloy was used to generate Sn-Co alloy nano particles at room temperature.In the meanwhile,liquid KNa alloy can also reduce graphene oxide.The as-produced Sn Co@RGO shows good cycle stability and rate performance.At the current density of100 m Ah g^-1,the first cycle has a discharge specific capacity of 1097 m A g^-1,and after 50cycles,there is still a discharge specific capacity of 655 m Ah g^-1,The discharge capacity of 415 m Ah g^-1 can be obtained at a current density of 5000 m A g^-1.3.Using triphenylbismuth as raw material,ethylene glycol dimethyl ether(DME)as solvent and liquid KNa alloy droplets as reducing agent and template,a two-dimensional bismuth metal nanosheet was synthesized by low-temperature solvothermal synthesis method and used as anode material for SIBs.When the liquid K-Na alloy was dispersed in DME,it exists as spherical droplets.Then the triphenylbismuth can be reduced at the liquid-liquid interface of the KNa alloy and DME.AS a result,the two-dimensional ultra-thin bismuth nanosheets were prepared at the surface of the liquid alloy.The nanosheet structure has a high specific surface area.As an anode material of sodium ion battery,it has a first discharge capacity of 659.7 m Ah g^-1.