Preparation And Sodium Storage Performance Study Of Sodium Titanate And Stannous Sulfide

Since Sony first released its first commercial lithium-ion battery in 1991,lithium-ion batteries have quickly entered people's lives.Compared with other rechargeable electronic devices,lithium-ion batteries are widely used due to their high energy density,high safety and stable cycle performance.Particularly,with the emergence of global warming in recent years,people are increasingly in demand of a kind of“zero-emission”energy.Electrochemical energy storage devices such as electric vehicles gradually enter people's daily life because they do not produce CO₂.However,with the large demand for lithium-ion batteries,on the one hand,the price of lithium will rise,and on the other hand,the amount of lithium on the earth is limited.Therefore,it is urgent to develop a new type of battery as an alternative to lithium-ion batteries.Since the sodium and lithium elements are located in the same main group and the electrochemical performance is relatively close,researchers have developed a strong interest in the research of sodium ion batteries in recent years.However,some chemi-cal differences between sodium ion and lithium ion hinder the industrial application of sodium-ion batteries.The differences between the two are mainly reflected in the following aspects:?1?The ionic radius of Na⁺?1.02??is larger than the ionic radius of Li⁺?0.76???2?The mass of Na atom?23 g/mol?is more than three times the mass of lithium atom?6.9 g/mol?.?3?The reduction potential of Na⁺?-2.71 V?is slightly higher than the reduction potential of Li⁺?-3.04 V?.At present,the positive electrode material of sodium ion battery is mainly the sodium salt of transition metal oxide,and the negative electrode material is mainly graphite,hard carbon and binary alloy.Although the initial capacity of the carbon material is high,the cycle performance is poor,mainly because the radius of the sodium ion is about 34%larger than the radius of the lithium ion,which makes it difficult for the sodium ion to be embedded in the carbon material.Therefore,the development of a sodium-ion battery anode material with superior cycle performance and high specific capacity is particularly urgent for solving the industrial application of sodium ion batteries.In this paper,two kinds of sodium-ion battery anode materials are studied.The specific research contents include the following two aspects:???Synthesis and characterization of Na₂Ti₃O₇ nanowire as sodium-ion battery anode material:titanium sheets were used as raw material,titanium sheets were hydrothermally heated in NaOH solution,and then annealed in different atmospheres.The prepared Na₂Ti₃O₇ anode material exhibits good sodium ion storage properties such as excellent electrochemical conductivity and good sodium-ion diffusion properties.When the phosphorus-doped sodium titanate(P-Na₂T_i3O₇)nanowire material prepared as the electrode and the sodium metal as the counter electrode are prepared into a sodium ion button half-cell,it can reach 270 mAh/g when its current density is 100 mA/g,and it can also reach 50 mAh/g for more than 3000 cycles at 20C.???Synthesis and characterization of spherical SnS/C as negative electrode materials for sodium ion battery:Pipe sealing machine was used to create a vacuum environment,and tetraphenyltin(C₂₄H₂₀Sn)and sulfur powder?S?were synthesized under vacuum to synthesize spherical SnS which is used as the anode material of sodium-ion battery.The synthesized SnS electrode material and sodium metal were assembled into the sodium ion button half-cell,and its specific capacity was maintained at 450 mAh/g or more after cycling 500 cycles at a current density of 0.1A/g.