EAGER: Exploiting Electrochemically-induced Phase Transformations in Mg-Li Thin Film Electrodes for Ultra-high Capacity Energy Storage

技术概要：研究了镁锂相变阳极在充放电过程中对镁薄膜进行电化学嵌锂/脱锂时的可逆相变机理。 本研究的关键概念是，从纯Mg阳极开始，在Li充电期间（和放电期间的相反），可以在阳极中诱导从HCP Mg到BCC Li-Mg的相变。关键问题是薄膜的微观结构变量如何影响电化学诱导相变的可逆性。 柱状晶的尺寸和间距，以及晶粒取向，是影响相变的主要变量。 该假设是，可以有一个最佳的晶粒尺寸和柱间距，容纳相变的体积变化，完全允许最大化的锂存储和去除，而不破坏电极。 这是一项高风险的研究，因为不能确定相变和体积变化调节的可逆性是否可以在电池所需的足够数量的循环中重复。具体而言，研究涉及通过溅射或PVD制造具有超细和柱状晶粒结构的各种厚度的Mg膜，使用MEMS制造技术进行微机械加工以扩展柱间距，测试电化学电池以了解在充电/放电期间从HCP Mg到BCC Li-Mg的可逆相变的性质，以及容量的实验测定，非技术性概述：下一代电动汽车，以及来自太阳能电池和风车的可再生能源的有效利用，将需要在电能存储和回收方面的重大技术突破。 提出了一个高风险和高回报的研究项目，利用锂镁合金阳极中的相变来帮助开发比目前考虑的电动汽车容量大得多的超高容量储能电池。这项研究可能会为新一代可靠的高容量电池带来新的电极材料和结构，从而加速低成本插电式电动汽车的发展。该项目将雇用一名研究生和一名或多名本科生，提供电池材料科学研究领域的教育和培训，并针对高中生开发推广/招聘演示文稿。这项研究将被纳入能源科学与工程研究生课程的电池材料科学课堂讲座。 在大学科学日招聘活动期间，还将以“能源材料科学”为主题向高中生和家长进行公众宣传。

TECHNICAL SUMMARY: Research is proposed to understand the mechanism of reversible phase transformations in Mg-Li phase-changing anodes during electrochemical insertion/removal of Li in Mg thin films during the charging/discharging processes. The key concept of this research is that starting with a pure Mg anode, a phase change from HCP Mg to BCC Li-Mg can be induced in the anode during Li charging (and the reverse during discharging). The key question is how the thin film microstructural variables affect the reversibility of the electrochemically-induced phase transformations. The size and intercolumnar spacing of the columnar grains, as well as the grain orientation, are the primary variables affecting the phase transformation. The hypothesis is that there could be an optimum grain size and intercolumnar spacing that accommodates the volume change of the phase transition, fully allowing maximization of Li storage and removal without the destruction of the electrode. This is a high-risk research, because it is not certain that the reversibility of phase transformation and volume change accommodation is repeatable over the sufficient number of cycles required in batteries. Specifically, the research involves making Mg films of various thicknesses with ultrafine and columnar grain structures, either by sputtering or PVD, micromachining using MEMS fabrication techniques to extend the intercolumnar spacing, testing electrochemical cells to understand the nature of the reversible phase change from HCP Mg to BCC Li-Mg and vice-versa during charging/discharging and experimental determination of the capacity, cyclability and stability of the performance during the charge/discharge cycles.NON-TECHNICAL SUMMARY: Next-generation electric vehicles, as well as effective utilization of renewable energy from solar cells and windmills, will require major technological breakthroughs in electrical energy storage and retrieval. A high-risk and high-payoff research poject is proposed to exploit phase transformations in lithium-magnesium alloy anodes to help develop ultra-high-capacity energy storage batteries with capacities much larger than those currently under consideration for electric vehicles. The research could potentially lead to new electrode materials and structures for a new generation of reliable and high-capacity batteries, which could in turn accelerate the development of low-cost plug-in electric vehicles. The project will employ a graduate student and one or more undergraduate students, provide education and training in the area of battery materials science research, and develop outreach/recruitment presentations aimed at senior high school students. The research will be integrated into class lectures on battery materials science for a graduate course on Energy Science and Engineering. Public outreach presentations, under the theme of "energy materials science", to high school students and parents during University Science Day recruitment events, will also be made.