| Since the1980s, rechargeable batteries had been widely and deeplydeveloped, at present, the secondary batteries have been widely used inpeople’s daily life and electric vehicles and other large energy storagedevice, but there are some challenges of secondary batteries, on onehand it requires the batteries with a smaller volume, lighter quality tomeet the needs of portable devices. Second, with the more and moreserious environmental problems it needs the material be moreenvironment friendly. Also the storage of the resource of battery materialitself is also a major challenge.At present there are many kinds of secondary batteries, lead-acidbatteries, sodium sulfur battery, magnesium battery lithium-ion batteryand sodium-ion battery, for now the research and application are mostlyfocus on the lithium-ion battery and the lithium-ion also had been widelyused, but there is a very big challenge for lithium-ion battery, the contentof lithium element in the earth’s crust is only0.002%, which limit theapplication of lithium-ion battery, especially there would be large-scalematrerial storage for big resource gap. The development of sodium-ionbattery may solve the problem of shortage of lithium element. Comparedto lithium-ion the sodium-ion battery has worse energy density, but withthe advantages of resource cheap price also the similar charge anddischarge make the sodium battery a very competeable product. Theanode and cathode material is the key factor for the application of sodiumbattery.Nowadays the cathode materials for sodium ion battery mainlyfocused on oxide AxMO2(x<1, A is an alkali metal element, M is atransition metal) etc., the anode material concentrated in graphite, hardcarbon and sodium binary alloys. A carbon electrode material has a high initial capacity, but the sodium ion is30%bigger than the lithium ion,when the carbon material used as the sodium ion battery anode materials,the cycle performance is very poor, so the researching of high capacity,high cycle performance anode material is very important. This paperfocused on two sodium ion battery anode materials TiO2and Na2Ti3O7,and modified the materials by graphene coating and so on.In chapter three we described the synthesis of titanium dioxidematerial and the modification of the material. TiO2were synthesized bysol-gel method, Tetrabutyl titanate was used as raw material. And thegrapheme was prepared by Hummers method, then use the spray-dryingmethod for graphene modifying TiO2. The percentage of graphene was2.27%wt,3.34%wt and6.58%wt wherein the spray-drying methodachieved a good performance of graphene modifying TiO2, and the3.34%wt of graphene had the best electrochemical performance. Theelectrochemical test shows that the titanium dioxide material has aspecific capacity of166.2mAh/g and the cycle characteristics is good,after100cycles still had a capacity of148.9mAh/g.3.34%wt of thegraphene coating material, had a large increase of the capacity of thematerial, it turns out to a initial capacity of220mAh/g，after100cyclesand the capacity retention at209mAh/g.In chapter four we described the different methods of synthesis ofsodium titanate materials and used graphene and multi-walled carbonnanotubes to modify the Na2Ti3O7, We used solid-phase synthesis methodand hydrothermal method. The reaction factor of Solid phase was850℃a nd20h. The reactionfactor of Hydrothermal was180℃and40h.The modification of graphene and Mwcnts were made by Hydrothermalmethod. The materials prepared by solid-phase and Hydrothermal methodas sodium ion battery had a separate capacity of77.4mAh/g and139.5mAh/g. the complex material with2.63%wt graphene and5%wtmulti-wall carbon nanotubes had a separate capacity of141.mAh/g and155.6mAh/g.After all TiO2and Na2Ti3O7used as the sodium ion battery anodematerials had a good experimental capacity, and a very good cycleperformances, it meet the requirements forming full battery. The method we had used to synthesis the materials is simple and easy to achieveindustrial production, so this paper provided a theoretical foundation forfuture research sodium ion battery anode materials. |
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