Nanostructured Electrochemical Materials

非技术描述：在这个项目中，氧化锡涂层的碳纳米管被用作模型材料来研究锂存储的机制。氧化锡因其高的锂离子储存容量而被认为是最有前途的锂离子电池金属氧化物负极材料之一。然而，氧化锡作为阳极材料的实际应用受到其在充放电循环期间的大体积变化（高达300%）的限制，这可能导致其崩解和与集流体的电断开。为了解决这个问题，通过在垂直排列的碳纳米管上生长氧化锡壳来开发三维碳纳米管-氧化锡核壳纳米线阵列。碳纳米管作为氧化锡壳的骨架来缓冲大的体积变化，而圆柱形氧化锡壳在锂化过程中抑制其降解。该项目的成果将有益于常规锂离子电池的研发，以及片上微功耗的开发。更好地理解电化学性质对于开发和合理设计用于锂离子电池的三维分级电极纳米材料具有重要意义。每年，这些研究人员提供两次公开讲座，传达材料科学和技术的新知识。在佛罗里达国际大学，一个为西班牙裔服务的机构，一群不同的学生正在从事这项研究。每年，研究生和本科生参加研究，他们有机会在桑迪亚国家实验室工作。每年邀请60名高中生和10名高中教师参加校园实验室图尔斯参观和研究演示。技术规格：碳纳米管-金属氧化物核壳复合材料作为锂离子电池负极材料具有广阔的应用前景。 然而，这类材料的电化学锂化-脱锂行为和机理尚不清楚。对纳米尺度下锂化机理的全面理解有利于高性能锂离子电池材料的设计和开发。本计画发展一种合成与表征垂直排列碳奈米管-氧化锡核-壳奈米线阵列的协同方法，以在合成时操控其电化学性质。采用等离子体增强化学气相沉积法在集流体上直接合成了垂直排列的碳纳米管阵列，并通过化学溶液法和气相沉积法在碳纳米管上合成了氧化锡壳层。通过电子显微镜、电子能量损失谱、能量耗散谱、X射线衍射（原位和非原位）、充放电测量、循环伏安、电化学阻抗谱和原位透射电子显微镜观察锂化过程，研究了碳纳米管-氧化锡核壳纳米线的微观结构和电化学性能。该研究为深入理解核壳纳米线阵列的锂化机理及其微观结构对其电化学性能的影响提供了理论依据。研究结果为碳纳米管-金属氧化物复合材料在锂离子电池中的电化学过程提供了新的见解。研究生和本科生接受先进的电化学材料合成，表征和设计的研究培训。

NON-TECHNICAL DESCRIPTION: In this project, tin oxide-coated carbon nanotubes are being used as a model material to investigate the mechanism for lithium storage. Tin oxide is considered one of the most promising metal-oxide anode materials for lithium ion batteries due to its high lithium ion storage capacity. However, the practical application of tin oxide as anode material is restricted by its large volume change (up to 300%) during charge-discharge cycles, which can cause its disintegration and electrical disconnection from the current collector. To circumvent this problem, a three-dimensional carbon nanotube-tin oxide core-shell nanowire array is being developed by growing tin oxide shells on vertically-aligned carbon nanotubes. The carbon nanotubes serve as the backbone of the tin oxide shell to buffer the large volume change, while the cylindrical tin oxide shell alleviates its degradation during the lithiation process. This project's outcomes will be beneficial to conventional lithium ion battery research and development, as well as on-chip micropower development. A better understanding of the electrochemical properties is making a significant contribution to the development and rational design of three-dimensional hierarchical electrode nanomaterials for lithium ion batteries. Each year, these researchers provide two public lectures to convey new knowledge of material science and technology. A diverse set of students are engaged in the research at Florida International University, a Hispanic-Serving Institution. Each year, graduate and undergraduate students participate in the research, and they have the opportunity to work at Sandia National Laboratories. Annually, 60 high school students and 10 high school teachers are invited for on-campus lab tours and research demonstrations. TECHNICAL DETAILS: Carbon nanotube-metal oxide core-shell composite materials are promising candidates for application as anode materials in lithium ion batteries. However, the electrochemical lithiation-delithiation behavior and mechanism of this type of materials remain unclear. A comprehensive understanding of the lithiation mechanism at the nanoscale benefits the design and development of high-performance lithium ion battery materials. This project develops a synergistic approach for the synthesis and characterization of vertically aligned carbon nanotube-tin oxide core-shell nanowire arrays to manipulate their electrochemical property at the time of synthesis. The vertically-aligned carbon nanotube arrays are synthesized directly on a current collector using plasma enhanced chemical vapor deposition, and the tin oxide shell on the carbon nanotubes is synthesized via chemical-solution and vapor deposition routes. The microstructure and the electrochemical properties of the carbon nanotube-tin oxide core-shell nanowires are being investigated by a combination of electron microscopy, electron energy loss spectroscopy, energy dissipation spectroscopy, X-ray diffraction (both in situ and ex situ), charge-discharge measurement, cyclic voltammetry, electrochemical impedance spectroscopy, and in situ transmission electron microscopy observation of the lithiation process. The study provides a better understanding of the lithiation mechanism of the core-shell nanowire array and the influence of their microstructure on their electrochemical properties. The research results provide new insight into the electrochemical process of carbon nanotube-metal oxide composite materials in lithium ion batteries. Graduate and undergraduate students receive research training in advanced electrochemical material synthesis, characterization and design.