| Stannous oxide(SnO),also known as Tin oxide,is a metastable material which is difficult to obtain from nature directly.As one of important metal oxide materials,SnO has unique advantages in many fields such as catalyst,reductant,glass industry,electrotinning and predecessor of stannous salt.In addition,SnO has a high theoretical capacity(875 mAh/g)which is much higher than those of traditional carbon anode materials.As an excellent anode material,SnO has made much attention in the field of lithium ion rechargeable batteries.It is well-known that the properties of nano-materials are greatly influenced by their shape,size and structures.Therefore,the preparation of stable single-crystalline SnO and high performance lithium ion battery using SnO as anode material has become a hotspot in the field of stannous oxide materials.In this thesis,size-and shape-controlled SnO micro/nano-materials had been successfully synthesized by solvent thermal approach using anhydrous stannous chloride,oleylamine(OLA)and Lithium bis(trimethylsilyl)amide(LBA)as material sources.Via an athermal decomposition process,including size-controlled bowl-shaped hollow structure and layered cube-shaped SnO micro/nanocrystals have been synthesized successfully.The crystal structure of these as-synthesized SnO was confirmed by using powder X-ray diffractometric(XRD)analysis.Compared with the standard PDF of SnO(JCPDS no.06-0395),the well-resolved peaks in the XRD pattern could be observed,indicating pure SnO materials had been synthesized.When reaction temperature between 130 to 180?,the purity SnO samples could be synthesized.At different reaction occasion,it can be seen that the bowl-shaped SnO crystals are formed by small particles and the diameter of the structures increse with the Ostwald ripening process by the reaction time increasing.However,when the reaction time exceed 1h,we found that the diameter of SnO samples decreased gradually due to redecompose process.Additionally,when the temperature exceeds the critical value(190?),the as-synthesized pure SnO samples changed to SnO-Sn composites,and finally became Sn completely.The reasonable reason attributed to using OLA and LBA during synthsis process.Both of OLA and LBA not only play the role of capping-ligand but also show weak reductibility.Therefore,with the reaction temperature rising,SnO materials conver to metal Sn by reduction reaction.The deep reason will be studied by following relevant experiment in the future.In addition,as anode material,all the obtained SnO samples mentioned above were tested as the electrical properties of the lithium ion battery.The results show that the electrical properties were different with the different diameters of SnO samples.Through contrast analysis,the sample with 1 ?m diameters of SnO exhibits the best Lithium ion battery performance.The initial capacity is 1235.8 mAh/g,and 371.4 mAh/g left after 50 cycles.The property is relatively excellent compared with the others reported by similar articles In addition,the bowl-shaped structure can improve the cycle performance of lithium ion battery.The effect of improving the cycle performance of lithium ion battery is better than any other shaped SnO structures proposed in previous other works.It's attributed to the interspace of cavity in the structure is expected to buffer well against the local volume change during the Li-Sn alloying and dealloying reactions,and beneficial for keeping the structural stability. |
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