Synthesis and Electrochemical Studies of Intercalated and Framework Substituted Silicon Clathrates

技术概要：在固态和材料化学项目的支持下，本项目将对硅包合物进行详细的结构和电化学研究。这些材料由共价键合在笼状结构中的硅组成，所述笼状结构由共享面的Si 20、Si 24和/或Si 28簇组成，所述簇可以通过在笼内掺入碱金属或碱性客体离子来掺杂。骨架取代的笼形物涉及用其他金属如Al和Cu取代硅原子。 该项目的主要目标是了解这些材料的电化学性能，以及它们的结构如何影响这些性能，以及硅包合物的结构如何在电化学插入客体离子后发生变化。将利用热熔融和电弧熔融等直接合成方法来制备骨架取代的硅包合物，然后通过电化学方法插入和去除客体离子。该项目的目标是锂，钠，镁插层硅包合物的合成和结构和电化学表征。可能的结果是：（1）掺杂有Li和Mg的新笼形物的合成，（2）关于硅笼形物结构中客体原子插入和移除的电化学的基础知识的创建，以及（3）氧化还原过程与硅笼形物中的结构变化的相关性。这些结果对锂、钠和镁离子可充电电池新阳极的开发具有重要意义。此外，与新型硅包合物（如Li和Mg插层包合物）的合成相关的新知识可能会引起研究硅包合物用于其他应用（如热电、超导、磁性和硬质材料）的研究人员的兴趣。电化学储能正日益成为技术和社会的重要组成部分，广泛用于便携式电子产品，并很快在电动汽车和光伏电网应用中发挥更大的作用。为了实现未来的能量存储需求，有必要寻找具有更高能量和功率密度的新电极材料。硅包合物材料具有笼状结构，可以自然地容纳客体离子，这是可以在能量存储应用中利用的特征。该项目旨在建立对硅笼形物结构如何影响可以电化学插入和移除的客体离子的类型和数量的基本理解，这些关键特性可以导致开发具有改进的电荷存储能力，机械完整性和循环寿命的新电池电极材料。该项目还将通过所涉及的实验和计算技术为研究生和本科生提供材料化学和电化学方面的广泛培训。虽然普通大众每天都在使用电池，但大多数人并不了解这些设备的私密细节。因此，基础材料研究的重要性和影响，因为它涉及到能量存储设备将通过在本科和研究生水平的教学，以及通过推广计划，以目标K-12学生和一般人群传播。该项目成果的广泛传播将提高公众对无处不在的储能设备如何工作的科学理解，也可能激发科学界对硅包合物材料在其他能源和电子应用中的应用的进一步研究。

TECHNICAL SUMMARY:With the support of the Solid State and Materials Chemistry program, this project will undertake a detailed structural and electrochemical investigation of silicon clathrates. These materials consist of silicon covalently bonded in cage structures comprised of face-sharing Si20, Si24, and/or Si28 clusters that can be doped by the incorporation of alkali or alkaline guest ions inside the cages. Framework substituted clathrates involve replacing silicon atoms with other metals such as Al and Cu. Key objectives of this project are to understand the electrochemical properties of these materials and how their structure affects those properties, as well as how the structure of the silicon clathrates changes upon electrochemical insertion of guest ions. Direct synthesis methods such as thermal and arc melting will be utilized to make framework substituted silicon clathrates, followed by electrochemical methods to insert and remove guest ions. The project aims are the synthesis and both structural and electrochemical characterization of Li, Na, and Mg intercalated silicon clathrates. Potential outcomes are: (1) the synthesis of new clathrates doped with Li and Mg, (2) the creation of fundamental knowledge regarding the electrochemistry of guest atom insertion and removal in silicon clathrate structures, and (3) the correlation of redox processes with structural changes in silicon clathrates. These outcomes have implications for the development of new anodes for Li, Na, and Mg-ion based rechargeable batteries. In addition, the new knowledge gained related to the synthesis of novel silicon clathrates (such as Li and Mg intercalated clathrate) may be of interest to researchers who study silicon clathrates for other applications such as thermoelectric, superconducting, magnetic, and hard materials. ON-TECHNICAL SUMMARY:Electrochemical energy storage is increasingly becoming an important component of technology and society, with widespread use in portable electronics and soon to be larger roles in electric vehicles and photovoltaic-grid applications. The search for new electrode materials with higher energy and power densities is necessary in order for the future energy storage demands to be realized. Silicon clathrate materials have cage-like structures that can naturally hold guest ions, a feature that may be exploited in energy storage applications. This project seeks to establish fundamental understanding on how the structures of silicon clathrates affect the type and number of guest ions that can be electrochemically inserted and removed, key properties that can lead to the development of new battery electrode materials with improved charge storage capabilities, mechanical integrity, and cycle life. This project will also provide broad training in materials chemistry and electrochemistry for students at the graduate and undergraduate level through the experimental and computational techniques involved. While batteries are used on a daily basis by the general public, most people do not understand the intimate details of these devices. Therefore, the importance and impact of basic materials research as it relates to energy storage devices will be disseminated through teaching at the undergraduate and graduate level, as well as through outreach programs to target K-12 students and the general population. The broad dissemination of the results of this project will enhance scientific understanding in the general public of how ubiquitous energy storage devices work and may also stimulate further research in the scientific community on the application of silicon clathrate materials in other energy and electronic applications.