【作者】 徐杨；

【导师】 谢毅；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2011， 博士

【摘要】 本论文旨在以目标化合物的结构分析为导向,结合有益的形貌特征,通过设计合适的化学反应路线实现钒氧基化合物微纳结构的可控合成,并考查所获得的钒氧基化合物微纳结构作为水溶液锂离子电池负极材料的电化学性能,对其晶体结构与电化学性能之间的结构-性能相关性进行初步探讨。本论文主要内容归纳如下:1.作者利用前驱物热解的方法实现了钒氧化合物新物相多孔微纳结构的制备,扩展了钒氧化合物作为水溶液锂离子电池负极材料的范围。我们利用简易的溶剂热方法合成海胆状微纳结构前驱物,并通过热转化获得了新介稳相V₂O₃多孔海胆状微纳结构。这一途径利用前驱物分子的功能性配体同时实现了新物相的产生和多孔结构的制备。我们将这种新介稳相V₂O₃多孔海胆状微纳结构作为负极材料应用于水溶液锂离子电池,首次实现了+3价钒氧化合物在该领域的利用。2.以目标化合物的结构分析为导向,作者利用Kirkendall效应,通过低温水热还原途径获得了具有特征孔道结构的黑铁钒矿VOOH空心海胆状微纳结构,在这种矿物结构被发现60年后首次实现了实验室人工制备。基于进一步结构分析,我们通过简易的低温褪火处理在保持空心海胆状形貌的同时实现了从黑铁钒矿VOOH到次铁钒矿VO₂的拓扑化学结构转化。我们将以上两种产物作为负极材料应用于水溶液锂离子电池,证明孔道状微观结构特征和空心形貌宏观特征对提高电池性能的促进作用,也进一步扩展了低价钒氧基化合物在该领域的应用。3.基于大多数钒氧基化合物纳米结构电极材料的电池循环性能不理想这一现象,以目标化合物的结构分析为导向,作者以简易水热途径获得的具有典型层状结构的Ag₂V₄O₁₁纳米带为例,首次研究了水溶液锂离子电池的电极反应机理。我们通过对处于充放电过程中不同阶段的电极材料进行细致的表征和分析,提出了分步反应的电化学机理,并且对电池比容量衰退的原因作了初步的探讨。这一部分的工作在之前工作的基础上,将研究范围从发现和设计合适的水溶液锂离子电池负极材料进一步扩展到考查探知水溶液锂离子电池的电极反应机理,以求能深入了解影响电池性能的因素,从而为将来更好的设计和评估其他电极材料提供一定的参考价值。4.受上一工作启发,作者通过针对性地寻找关键的结构单元,从晶体结构的角度对如何提高水溶液锂离子电池的循环性能做了有益的探索。我们提出,在金属钒氧基化合物相邻钒氧层之间引入起支撑作用的结构单元来连接相邻钒氧层,进而将典型的二维层状结构转变为三维孔道结构,这种“支撑效应”将有效抑制层状结构由于锂离子频繁嵌入和脱嵌而导致的结构塌陷,从而可以提高电池的循环稳定性。我们选用具有二维层状结构的Ag₂V₄O₁₁和三维孔道结构的β-钒青铜Ag_0.33V₂O₅为例,通过对比这两种负极材料的循环性能阐述了关于“支撑效应”的观点,并进一步通过对另一β-钒青铜Na_0.33V₂O₅的电池性能测试证明了这一效应在该结构体系中的普适性。更多还原

【Abstract】 The goal of this dissertation is to explore the controllable synthesis of vanadium oxides based micro-nanostructures with favorable morphologies by understanding the crystal structural characteristics of the target products and developing novel chemical reaction routes. On the basis of the unique microscopic crystal structures, new application of these vanadium oxides based micro-nanostructures has been further developed as active anode materials for aqueous lithium ion batteries, and the corresponding structure-property relationships have been also investigated in this dissertation. The details are summarized briefly as follows:1. We successfully synthesized new-phased metastable V₂O₃ porous urchin-like micro-nanostructures by a simple top-down precursor-pyrolyzation strategy. The generation of new phase and preparation of porous morphology were simultaneously realized by using functional ligand in precursor molecules. We introduced these new-phased metastable V₂O₃ micro-nanostructures as active anode materials for aqueous lithium ion batteries, realizing the application of vanadium （III） oxides in this electrochemical energy storage and conversion system for the first time.2. We developed an available pathway to accomplish the synthetic montroseite VOOH hollow nanourchins with typical tunneled crystal structure after sixty years of delay. Paramontroseite VO₂ with same morphology was converted from montroseite VOOH through a topochemical transition strategy due to the extreme structural similarity revealed by crystal structure analysis. We investigated their electrochemical properties as anode materials for aqueous lithium ion batteries, further expanding the application of vanadium oxides based compounds with low valence in this research area.3. We investigated the charge-discharge reaction mechanism of aqueous lithium ion batteries for the first time by taking a new anode material of single-crystalline Ag₂V₄O₁₁ nanobelts as an example on the basis of its typical layered crystal structure. A two-step reaction mechanism was proposed and the reason for rapid capacity fading was also deduced.4. We successfully demonstrated the crystallographic pillar effect on cyclability enhancement for aqueous lithium ion batteries by comparing the electrochemical cycle performance of a new anodeβ-vanadium bronze Ag_0.33V₂O₅ nanowires with 3D tunneled structure and Ag₂V₄O₁₁ nanobelts with 2D layered structure. The significant role of this pillar effect was further verified by an extension of another new anode material of Na_0.33V₂O₅ nanowires.更多还原