Controllable Synthesis And Properties Of Tin Monoxide Shell Structure

In the past ten years,the research on nanomaterials has made significant progress.People have prepared various micro/nano structures of nanomaterials,such as shell structure,to realize the control of material properties and expand their applications.As one kind of semiconductor metal oxides,tin monoxide?Sn O?has the characteristics of environmental friendliness,economy,and stability.It has been used in gas sensors,lithium ion batteries,and electronic devices.Studies have shown that the crystallinity and morphology of tin monoxide have very important influence on properties of the material and even its application.Recently,with the deep research of layered material systems,new understanding and exploration of layered materials such as tin compounds?Sn O,Sn S Sn S₂ and Sn Se₂ etc.?have been made.Based on the structure diversity of tin compounds,more properties have been discovered through the adjustment of its micro/nano structures,which greatly improved the performance of the above applications.This dissertation studied controllable synthesis of tin monoxide shell structure and regulation of its physical properties,and further studied the characteristics of the material used as active layer of ammonia gas sensors and anode material of lithium ion batteries.The main contents include the following three parts:?1?Through solution method and annealing,we prepared tin monoxide nanoshell.The morphology and structure of as prepared samples were investigated by field emission scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?and Raman spectroscopy.We controlled the size of material by adjusting the concentration of reactant in solution that was analyzed by transmission electron microscopy.The photoluminescence was tested by 514.5 nm incident light with 0.5 m W.The experiment exhibited the size of samples was 30-60 nm when concentration of stannous chloride dihydrate in solution was 0.005 mol/L-0.01 mol/L respectively.Under 514.5 nm excitation light,samples with shell sizes of 30,45,and 60 nm had peak emission positions of 616 nm?2.02 e V?,612 nm?2.03 e V?,603 nm?2.06 e V?,respectively,and the intensity of photoluminescence increased.This result indicated that when the concentration of the reactants in the solution for synthesizing tin monoxide nanoshell structure was higher,not only can larger shell structure be formed during the reaction,but also more oxygen vacancies can be formed during annealing.Our research has realized control of size of tin monoxide shell structure,and also revealed formation regulation of the defect density of the material.?2?Based on the above method,five samples under different annealing conditions were obtained.The changes in the structure of tin monoxide nanoshells under different annealing treatments and their influence on the sensing performance of ammonia gas were studied,and extremely high sensitivity,good selectivity,and response/recovery speed were obtained.It was found that only samples prepared by heating from room temperature for 1 h to 300°C and then maintaining temperature of300°C for 1 h and finally natural cooling had largest number of shell structures.Ammonia sensors based on the sample exhibited high responses?S=?G_g-G_a?/G_a*100%?of 313%,874%,2757%,3116%,and 3757%under gas concentrations of 5 ppm,20ppm,50 ppm,100 ppm,and 200 ppm,respectively,which is much higher than other samples.This material also showed good selectivity and response/recovery rate?response time of 98 s and recovery time of 30 s?in ammonia sensing.The systematic analysis showed that the excellent sensing performance of the tin monoxide nanoshell structure was mainly attributed to the layered shell structure and high-density oxygen vacancy defects.This work can expand the potential of IV–VI metal oxides with similar structure applied in gas sensors.?3?We further studied performance of the tin monoxide nanoshell as anode material for lithium ion batteries,and revealed the buffering effect of the large specific surface area of nanoshell structure on charge and discharge volume expansion.Based on the previous research on the preparation and micro/nano structure of tin monoxide nanoshell structure,we applied it to anode materials of lithium ion batteries.The result exhibited samples with the largest number of tin monoxide shell structures processed by optimized annealing conditions showed the best lithium electrical properties.After 30 charge\discharge cycle tests of that material with current density 1Ag^-1 and 0.1 Ag^-1,discharge capacities reached 497.5 m Ahg^-1 and 559.3 m Ahg^-1respectively,which were much higher than graphite.For the comparative analysis of the morphology and structure of different samples,the key to the excellent lithium ion battery performance of the sample is the density of the shell structure.The performance of the material is improved by increasing the ion channel and buffering the volume expansion.The result of this work demonstrated the potential of tin monoxide shell structure in applications of lithium ion batteries.