Synthesis And Electrochemical Performance Of Tin Anode Materials For High Performance Lithium Ion Battery

With the development of science and technology,sustainable development has become an trend.However,with the rapid development of economy,a large number of non-renewable resources such as oil,coal and natural gas are consumed,which not only seriously threatens the future development,but also brings serious environmental pollution problems.Lithium ion batteries,as a new type of energy,has attracted great attention due to its advantages of small pollution,no memory effect and high energy density.But commercial lithium ion batteries still have some disadvantages,such as high cost,easy to lose control of heat,low capacity and other problems,which restrict their application in other fields.At present,commercial lithium ion battery is the graphite as cathode mateial,which the theoretical capacity of the graphite is only372 m Ah g^-1.However,the theoretical capacity of the metallic tin(990 m Ah g^-1)is about 2.5times that of graphitem and the metallic tin has good conductivity.Unfortunately,the biggest challenge for this kind of metallic tin as active anode materials is that it is suffering from huge volume variation,making the active material fall off from the collector,which leads to poor cycling performance,and hinders the commercial application.In order to solve the problem,we successed prepared some new 3D network structure and nanochip structure tin-base mateials with the method of template,and carried out corresponding characterization test and electrochemical performance test.The main research work of this paper has the following three aspects.（1）In the process of preparation,the tin source of tin chloride dihydrate（SnCl₂·2H₂O）and the EDTA both of carbon source and nitrogen source with the assistance of cubic Na Cl particles as template.The 3D carbon skeleton mateial was synthesized by a freeze-drying technology and in situ reduction method,and denoted as Sn/NC.The Sn/NC composite power was heated to 550℃under argon atmosphere,and the tin nanoparticles embedded in the carbon network.The archical carbon network can increase the contact area between active material and electrolyte and short the transport path of lithium ion,which improves the cycling stability.At the current density of0.5 A g^-1,the electrochemical perpormance of Sn/NC composite has specific capacity of 1523m Ah g^-1even after 500 cycles.The current density is 0.2 Ag^-1and 5 A g^-1,the capacity still remains at 1556.9 and 697 m Ah g^-1,respectively,when the current density returns to 0.2 A g^-1,the capacity can returns to 1402.8 m Ah g^-1,which shows excellent electrochemical performance.（2）In the process of preparation,the tin source of tin chloride dihydrate（SnCl₂·2H₂O）,the cobalt source of Co Cl₂·6H₂O and the EDTA both of carbon source and nitrogen source with the assistance of cubic Na Cl particles as template.The 3D carbon skeleton mateial was synthesized by a freeze-drying technology and in situ reduction method,and denoted as SnCo/NC.The SnCo/NC composite power was heated under argon atmosphere,and the SnCo alloy nanoparticles embedded in the carbon network.The SnCo alloy nanoparticles can buffer the internal stress caused by volume expansion of Snduring the process of charge/discharge.The SnCo/NC composite delivers a high reversible capacities of 705 and 305 m Ah at the current densities of 0.2 and 5 A g^-1.At the current of 1 A g^-1,the SnCo/NC composite after 600 cycles remains a capacity of 810 m Ah g^-1.（3）Commercial metallic tin powders,SnCl₄·5H₂O,Na₂Mo O₄·2H₂O,NH₂CSNH₂and citric acid were used without further purification.SnS/Mo S₂/C was prepared by the method of planetary ball milling using Na Cl particles as the template.In addition,the SnS and Mo S₂nanoparticles were distributed in carbon sheets,and the presence of Mo S₂/C nanosheet maintains the structural stability and enhances the mechanical strength of the composite durring the cycling process.This SnS/Mo S₂/C composite exhibits excellent electrochemical performance,especially the first columbic efficiency is as high as 90.2%.When evaluated as anode for making button batteries,the ternary SnS/Mo S₂/C has a high revesible capacity(840 m Ah g^-1at 0.5 A g^-1after 250 cycles and 514.5 m Ah g^-1at 1 A g^-1after 500 cycles).