SusChEM: Design and Manufacture of Electrodes for High Energy Density Rechargeable Sodium Batteries

能够储存大量能量的可充电电池在移动电子和电动汽车等应用中是当今社会的一项关键技术。未来，这种电池也将成为商业和家庭电力中使用可再生能源的关键技术。如今这种可充电电池最广泛的使用形式是锂离子电池。用更低的成本和更丰富的元素钠(即食盐中的常见元素)取代锂将会有好处，锂在这些电池中是一种有点昂贵和稀缺的元素。改用钠可以降低电池的成本，并允许相同大小的电池存储更多电力。然而，从锂到钠的转换是具有挑战性的，因为电池的其他组件目前与钠的使用不兼容。特别是，当在电池中使用钠时，收集此类电池产生的电流的电流材料很快就会损坏。该项目的目标是通过开发能够成功应用于钠离子电池的新电极材料来解决这一重大挑战。除了这项技术可能对交通和可再生能源产生的直接科学影响和更广泛的影响之外，该项目还将通过研究生、本科生和高中学生的教育来支持关于能源储存的跨学科研究。这项研究为公众和K-12年级的学生提供了一个极好的平台，让他们了解科学和工程对社会的价值，并将通过休斯顿地区的一项高中推广计划，吸引女性和第一代大学生进入科学、技术、工程和数学(STEM)领域。这项工作的中心假设是，空间效应可以通过增加电池电极中使用的插层骨架的晶格间距来减轻或消除。这项研究的目标是开发出通过化学分层-重新堆积的方法来调节层状材料的层间距离的方法，这种方法可以改善离子在插层框架中的传输和离子的调节。这项工作结合了电化学、计算和微观表征实验来了解这种方法的设计和行为，重点是开发和理解用于高性能充电钠电池的具有MoO_3片层和聚合物层交替层状结构的钼金属氧化物MoO_3-聚合物纳米复合材料。该计划的主要特点包括精确控制具有所需层间距的MoO3-聚合物纳米复合材料的合成，通过电化学比较锂、钠和钾在这些复合材料中的插层动力学来表征离子尺寸对此类复合材料中插层行为的影响，以及通过密度泛函理论建模和原位电子显微镜观察对钠在扩展的MoO_3结构中的插层过程进行原子学理解。这项工作的结果将导致在原子水平上操纵二维无机层状化合物作为用于电池电极材料的大阳离子插层的有利主体材料的一般策略。

Rechargeable batteries that can store a large amount of energy are a critical technology for society today in applications such as mobile electronics and electric vehicles. In the future, such batteries will also be a critical technology for use of renewable energy sources in commercial and home electric power. The most widely used form of such rechargeable batteries today is the lithium ion battery. There would be benefits to replacing lithium which is a somewhat expensive and scarce element in these batteries with the much lower cost and more abundant element sodium (i.e., the common element found in table salt). The change to sodium could lower the cost of the battery and could allow for the same size battery to store more power. However, this switch from lithium to sodium is challenging since the other components of the battery are not currently compatible with use of sodium. In particular, the current materials that collect the electric current produced by such batteries are damaged quickly when sodium is used in the battery. The goal of this project is to solve this major challenge by developing new electrode materials that can successfully be used in sodium ion batteries. In addition to the direct scientific impact and the broader impacts in transportation and renewable energy that could be enabled by this technology, this project will support interdisciplinary research on energy storage with education of students at the graduate, undergraduate, and high-school levels. This research makes an excellent platform in which to engage both the public and K-12 students on the value of science and engineering to society and will be used through a Houston-area high school outreach program to attract female and first generation college students to Science, Technology, Engineering, and Mathematics (STEM) fields. The central hypothesis of this work is that steric effects can be alleviated or eliminated by increasing the lattice spacing of the intercalation frameworks used in battery electrodes. The goal of this research is develop methods to tune the interlayer distances of layered materials through a chemical delamination-restacking approach that can allow for improved ion transport and ion accommodation in the intercalation framework. This work combines electrochemical, computational, and microscopic characterization experiments to understand the design and behavior of such an approach, with the focus of the work on development and understanding of a molybdenum metal oxide MoO3-polymer nanocomposite featuring an alternating layered structure of MoO3 sheets and polymer layers for high performance rechargeable sodium batteries. Key features of the plan include the precise control of the synthesis of MoO3-polymer nanocomposites with desired interlayer distances, characterization of the influence of ion size on intercalation behavior in such composites by electrochemically comparing the intercalation kinetics of lithium, sodium, and potassium in these composite materials, and the formulation of an atomistic understanding of the intercalation process of sodium in the expanded MoO3 structures by density functional theory modeling and in-situ transmission electron microscopic observation. The results of this work will lead to a general strategy to manipulate two-dimensional inorganic layered compounds at the atomic level as favorable host materials for intercalation of large cations for use in battery electrode materials.