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

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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.