Study On Preparation Of Tin-based Nanofibers And Sodium Storage Properties By Electrospinning

In recent years,the continuous petrochemical energy crisis has caused not only environmental pollution which makes trouble for human beings,but also the daily decreasing reserve which is also a huge problem in the contemporary society.At present,influenced by weather conditions and seasonal changes,the electricity generation of renewable resources such as solar energy and wind energy fluctuates greatly,and the cost of energy storage system is relatively high.With the rapid development of electronic technology,people gradually have higher requirements for electronic products,meanwhile,traditional nickel-cadmium batteries and nickel-hydrogen batteries cannot meet the requirements of the public for energy-saving,low-consumption,compact and portable electronic products,therefore,it is extremely urgent to develop the energy storage technology.The development of lithium-ion batteries(LIBs)helps human beings become less dependent on non-renewable resources,and LIBs can be applied to various electronic products for safety,long cycle life,long endurance,environmental protection,fast charging and discharging,foldability and other characteristics.Meanwhile,in recent years,with strict government control of vehicle emission,major automobile companies have been working on the development of electric vehicles,and new of them have developed rapidly owing to a series of national policies.Nevertheless,large-scale use of lithium resource is also not a long-term strategy,so researchers have found an energy storage battery with similar electrochemical performance as LIBs:sodium ion batteries(SIBs).As a common anode material in LIBs,carbon material has the characteristics of good conductivity,small expansion coefficient,low platform and so on.However,in the process of battery charging and discharging,some carbon materials cannot fully accommodate Na~+because the diameter of Na~+is larger than that of Li~+,which finally causes material volume expansion,structure collapse and other problems.Therefore,in recent years,it is also a hot research topic to seek suitable electrode materials.For the above-mentioned problems,in this thesis,with the respective advantages of carbon materials and transition metal compounds,an electrostatic spinning experimental scheme is adopted to create the carbon-based transition metal compound,nanofiber,as the negative electrode material for sodium ion batteries.Through a series of characterization methods,the morphology and structure of the material have been characterized to explore the sodium storage performance of the material.The main work of this paper is as follows:(1)In the second chapter of the thesis,with the electrospinning method and selenium powder directly added into precursor solution for electrospinning,SnSe carbon nanofibers(SnSe@CNFs)are successfully prepared,and the one-dimensional(1D)structure of SnSe nanoparticles encapsulated in CNFs is synthesized.However,SnSe nanoparticles protected by the carbon layer can not only improve the transfer rate of electrons in the material,but also alleviate the structural expansion and disintegration of CNFs in the process sodiation/desodiation,to avoid the final rupture of the polar sheet.As the anode of the half battery,SnSe carbon nanofibers-1(SnSe@CNFs-1)anode material exhibits the discharge capacities of 326 m Ah/g at 0.1A/g after 100 cycles and 249.4 m Ah/g at 1 A/g after 900 cycles at room temperature(25°C).It still exhibits stable electrochemical performance at low temperature(0°C)after 100 cycles of 267 m Ah/g at 0.1 A/g.This design not only improves the rate of electron transmission,but also prevents SnSe nanoparticles from agglomerating and buffering the large volume changes of electrode material during sodiation/desodiation processes.This strategy also helps to alleviate pulverization of anode material during the recycling process and improve the cycle stability.(2)In the third chapter of the thesis,the same method of electrospinning was used to add sulfur powder directly to the precursor solution for electrospinning.The carbon nanofiber(SnS@CNFs)material with carbon coating SnS nanoparticles was successfully prepared.When applied to SIBs as negative electrodes,the capacity hardly decayed after 100 cycles of high current density of 1 A/g,and remained at about 330m A/g.This work can provide new ideas for other new metal sulfide electrodes.