Syntheses And Properties Of Multi-shelled Tin-based Hollow Microspheres And Polynuclear Coordination Polymers

Energy shortage and environmental pollution have become urgent problems for the scientific researchers nowadays. Lithium-ion batteries(LIBs) have drawn great attention as energy storage medium. Among various kinds of metal oxide electrode materials, Sn O2 has been extensively studied as a fascinating anode material for lithium battery due to its environmental benignity, low cost and high theoretical capacity. Tin oxides are different with Fe2O3 and Co3O4, which suffer from larger volume variation to form Li-alloys during the lithium alloying-dealloying electrochemical process. In recent years, Sn-based electrode materials with diverse morphologies have been reported to solve this problem. It is noteworthy that multi-shelled(MS) hollow structure materials are thought to be an attractive candidate,because the multi-shelled hollow microspheres with high surface area enable an increased electrode-electrolyte contact area, resulting in a larger gravimetric capacity.Moreover, they can offer more lithium storage sites and shorten the Li+ion diffusion length. Whereas, design and synthesize multi-shelled Sn-based hollow structure will be an effective path to improve cycling stability for lithium batteries.Using nano metal-organic frameworks(MOFs) as sacrificial materials to obtain highly controlled porous carbon or porous metal oxides have received increasing attention in recent years. Introducing MOFs to develop nanostructured materials hasbeen boosted by the fact that MOF derived materials always have high BET surface area, porosity and uniform shapes. MOF-based MOx provide another unique feature in material fabrication by allowing the existence of multiple metallic species in the same framework. Because of these advantages, MOF materials have been successfully used to develop nanostructure carbon, MOx, composites(M/MOx@C) and nanoparticle decorated MOFs. Therefore, MOFs-templated synthesis strategy has emerged to be a promising candidate to tailor MOF composites, which could be used for electrochemical energy storage and other applications.Polynuclear coordination polymers have attracted a growing attention for their thermodynamic and chemical stability. As a consequence, design and synthesis of coordination polymer with polynuclear metal centers will be a meaningful work for investigating properties and post-grafted modification.In this thesis, lithium-ion storage properties of various morphology Sn O2 hollow microspheres and MOF-templated composite materials TS-Sn O2@Fe2O3 have been studied. And eight new polynuclear coordination polymers have been successfully solvothermally synthesized. The key results are shown as below:1. A series of multi-shelled Sn O2 hollow microspheres were successfully prepared. Uniform single-, double-, triple-, and quadruple-shelled Sn O2 hollow microspheres were achieved by adjusting the concentration of Sn4+ aqueous solution under the same thermal processing procedure. Core-shelled Sn O2 hollow spheres can be easily obtained by using Sn2+ ions instead of the Sn4+ ions in ethanol/water mixture solution and increasing the speed of calcination. The electrochemical properties of multi-shelled Sn O2 hollow microspheres as anodes for LIBs were investigated. All of these materials exhibit well rate capacity, good cycling performance and superior structure stability after 50 th cycles. It is worth noting that, triple-shelled Sn O2 hollow microspheres showed higher specific capacity and better cycling stability(750m Ah?g-1 be remained at the 50 th cycle for the triple-shelled at a current density of 100 m A?g-1, voltage window 0.005-3 V).2. A series of hybrid multi-shelled hollow structure MOx@MOFs composites are successfully designed and synthesized by a universal method. The differentmetallic source can be selected and the thickness of MOFs shell can be well controlled by adjusting the repeat times or reactant concentration. More importantly,this work provides a novel and univerisal strategy to design and synthesis of MS-MOx@MOFs, MS-carbon, MS-MIOx@MIIOy-C and MS-MIOx@MIIOy materials.The representative hybrid MS-Sn O2@ ?-Fe2O3 exhibit not only excellent porous multi-shelled hollow structure but also superior cycling stability and rate performance.3. We have successfully synthesized two benzenedicarboxylic acids ligands with different substituents, NO2-H2 EDDC and NH2-H2 EDDC. By introducing different modulators in the solvothermal system, we have assembled eight MOFs(compounds 1-8) consisted of a series of linear ligands and different metal sources.Compounds 1-3 are isostructural Zr-MOFs based on Zr6O4(OH)4(CO2)12 SBUs. All three compounds feature an octahedral cage with the diameter of 24.6 ? and a tetrahedron cage with the diameter of 17.4 ?. Compound 4 is a two-fold interpenetrated framework based on(Fe3O)(CO2)6 SBUs and it possesses an one-dimensional channels along c axis with the diameter about 21.4 ?. Nevertheless,the channels are interpenetrated in nature, leaving quadrilateral channels with a window size about 18.7 × 10.7 ?2(regardless of the van der Waals radius).Compounds 5-8 are also isostructural fcu-topological based on RE6(?3-OH)8(CO2)12SBUs and all of them exhibit high thermal stability.