Research On Preparation And Electrochemical Performance Of Tin Dioxide As Anode Material For Lithium-Ion Batteries

Due to the rapid development of the information age and the increasingly prominent environmental problems,mankind is eager to find a new type of clean and recyclable energy.Lithium batteries are considered to be one of the most practical and widely used in energy storage field.They have been used in various portable devices,electric vehicles and may even be used in future power grid construction.Recently,new energy vehicles and various electric portable devices have put forward higher requirements on the performance of lithium-ion batteries,such as energy density and power density.The positive and negative electrodes of lithium-ion batteries directly affect the lithium storage mechanism.Therefore,it is necessary to explore a high-capacity and high-reversibility lithium battery electrode material to improve the electrochemical performance of the battery to meet people's higher requirements.The purpose of this paper is to prepare high-performance anode materials.In the family of anode material,the high lithium storage capacity of SnO₂(theoretical specific capacity of1490 m Ahg^-1)and the moderate lithium insertion potential have been paid great significance by scientific researchers all over the world.However,the capacity loss and serious volume expansion of SnO₂ during the cycle affect its practical application.In response to the above problems,several effective strategies have been proposed to improve the electrochemical performance of SnO₂:the preparation of nanostructured SnO₂,such as nanowires,nanoarrays,and hollow nanospheres;or the preparation of special structures,such as core-shell and nanoflowers,nanobelt structures.These methods alleviate the volume expansion of SnO₂during cycling;in addition,compounding with other materials is also a powerful means.For example,transition metals or transition metal oxides can effectively increase the irreversible capacity of SnO₂ electrode materials.Based on the above research background,the main research contents of this paper are as follows:(1)SnO₂ nanoparticles were prepared by a one-step hydrothermal method,and then SiO₂and graphite were added to prepare SnO₂@SiO₂/Graphite composites by a two-step ball milling method.In the ball milling process,SnO₂ and SiO₂ are evenly embedded on the graphite sheet,and the above results can be accurately obtained from the SEM,TEM,and EDS analysis.The SnO₂@SiO₂/Graphite electrode material exhibits good electrochemical performance.At a current density of 200 m A g^-1,the initial discharge specific capacity of SnO₂@SiO₂/G electrode material reaches 2489 m Ahg^-1,and it has a reversible capacity of1258.5 m Ahg^-1 after 80 cycles,and has a good rate performance,with a capacity of 395.6m Ahg^-1 at a current density of 5000 m Ag^-1.This excellent electrochemical performance can be attributed to the coating of graphite flakes,which can enhance the conductivity of the electrode material and alleviate the volume expansion of SnO₂.Secondly,SiO₂ will generate inactive Li₄SiO₄ and Li₂O,further alleviating the volume expansion of SnO₂.(2)SnO₂ nanospheres were prepared by a simple hydrothermal method,SnO₂@MoO₃composite materials were prepared by ball milling SnO₂ and MoO₃,and then SnO₂-MoO₃-CNT composite material was prepared by ball milling with carbon nanotubes(CNT)and the above composite material,SnO₂ and MoO₃ are both connected by CNT.The SnO₂-MoO₃-CNT electrode material exhibits excellent electrochemical performance.At a current density of 200 m Ag^-1,the initial discharge specific capacity of the SnO₂-MoO₃-CNT electrode material reaches 2278.4 m Ahg^-1,SnO₂-MoO₃-CNT retains a reversible capacity of 1372.2m Ahg^-1 after 280 cycles,and has excellent rate performance.It still maintains capacity of743.6 m Ahg^-1 at a current density of 5000 m Ag^-1,and high capacity of 899.6m Ahg^-1 at a current density of 1000 m Ag^-1 after 950 cycle.This excellent electrochemical performance can be attributed to the fact that CNT can enhance the conductivity of the electrode material.In addition,MoO₃ can promote the conversion of inactive Li₂O and Sn into SnO₂ and stabilize the structure of the electrode material.(3)Using NaCl,SnCl₂·2H₂O,citric acid,phytic acid as the template,tin source,carbon source,and phosphorus source respectively,then add deionized water by wet ball milling and mix uniformly.the precursor is obtained after drying,and then heat treatment is used.The organic matter is carbonized,and the template is suction filtered to obtain SnO₂/Sn P_x/C electrode material.The raw material is non-toxic and the preparation process is simple.The SnO₂/Sn P_x/C electrode material has a porous nanosheet structure,which can fully infiltrate the electrolyte,provide sufficient active sites,and accelerate the kinetic process of ions.In addition,the amorphous carbon in the outer layer can alleviate the volume expansion of SnO₂during charging and discharging.The synthesized SnO₂/Sn P_x/C composite material has excellent electrochemical properties:the discharge specific capacity is 1821.5 m Ahg^-1 at a current density of 200 m Ag^-1,and the discharge specific capacity remains 1139.2 m Ahg^-1 after150 cycles.At a high current density of 5Ag^-1,the reversible capacity reached 718 mAhg^-1 when it was cycled to 2000 cycles.