The Controlled Self-assembly And Device Application Of SnO₂Micro/nano-structures

SnO₂, an n-type semiconductor with favorable chemical and physical properties,has been researched extensively in the fields of gas sensors and lithium ion batteries.As a kind of potential anode material for lithium ion batteries, it is attractive for itshigh energy density, low cost and safety. However, the practical application of SnO₂ishampered by the drastic specific volume change （about358%）, which leads to poorcyclability. In the domain of gas sensor, great efforts should be directed to furtherpromote the sensitivity and response rate. The reported results indicated that theperformances of SnO₂greatly depended on its morphology and structure. In this thesis,considering the different features and demands, we prepared three kinds of novelSnO₂nanostructures by simple route. Their electrochemical performances and gassensening properties were investigated.In chapter2, SnO₂monolayer hollow spheres were prepared by controlledprecipitation and later calcinations with carbon spheres as templates. Multilayer andmonolayer hollow spheres can be obtained by turning the calcinations temperature.The sensors based on SnO₂monolayer hollow spheres showed much improvedsensitivity compared with these multilayer ones. The sensitivity to100ppm ethanolwas enhanced to51. We attributed this enhancement mostly to the enhanced depletioneffect arising from the increased exposed surface. Our results provoke a direction toimprove the performance of gas sensor by using monolayer porous hollow spheres.In chapter3, SnO₂mesoporous spheres for lithium ion battery anode materialswere obtained by a simple green route, which could be scaled up easily. These sphereswere porous, assembled by nanoparticles around5nm. The electrochemical testshowed that the as-prepared SnO₂mesoporous structure showed extraordinaryexcellent retention ability. It could deliver761mAh g^-1reversible capacities after50cycles at the current density of200mA g^-1. Even at high current density of2A g^-1, itstill can retain about480mAh g^-1after50cycles. We researched the possibleformation mechanism for this structure and reason for this great enhancement.In chapter4, we reported the synthesis of hierarchical SnO₂hollow nanostructureby one step method. The SEM and TEM results revealed that the hierarchical SnO₂architectures were porous and hollow, consisting of nanosheets. To understand theformation process of structures, we investigated the intermediate products at different reaction time and temperature. This structure was suitable for both lithium ion batteryand gas sensor. The primary electrochemical test exhibited high capacity andexcellent cycle performance. In addition, when utilized as active material for gassensors, they manifested promising gas sensing performances.