Interfacial Science and Defect Engineering of Functional Oxides for Na-ion Storage and Transport

非技术描述：在过去十年中，对替代能源的需求显著增加。陶瓷已经彻底改变了现代技术，如电动汽车，更重要的是，通过使用可充电的电化学储能系统，将化学和电子过程结合起来，将化学能转化为电流，从而实现了可再生能源的存储。钠（Na）嵌入陶瓷在实现可充电钠离子电池作为关键的大规模储能系统方面发挥着关键作用。钠资源天然丰度高，分布广泛，具有显著的成本优势。然而，钠离子电池还没有充分发挥其潜力；因此，开发高能量和功率密度的材料以进一步改进该技术势在必行。该项目旨在发现新的高性能材料，并探索陶瓷的界面科学和缺陷工程。通过采用系统的方法，使用一套功能强大的分析工具与第一性原理计算建模相结合，有可能确定新型陶瓷材料中用于能量存储和转换的基本机制，在这种情况下，是钠离子存储材料。研究和改进钠离子电池的陶瓷正极材料，通过为对材料科学和工程感兴趣的当地代表性不足的高中生开展外展活动，为下一代研究科学家提供了重要的机会。技术细节：在电化学过程中，由于一阶和二阶相变引起的结构变化会影响系统的电化学性能，这在电压分布中是显而易见的。此外，细微但关键的变化发生在电极-电解质界面，限制了用于储能的任何陶瓷材料的寿命。本研究极大地提高了对这些结构相变和表面/界面修饰的理解，同时探索了它们对钠离子插入化合物中离子传输和电荷转移的影响。在钠嵌入陶瓷材料上进行了各种类型的表面改性，包括碳涂层、溶胶-凝胶涂层和原子层沉积涂层。先进的表面探针技术正被应用于发现钠电化学电池表面/界面结构和化学性质的变化。这项工作的目的是确定：1)促进钠离子迁移增强的结构因素；2)离子输运和电荷转移的界面效应；3)缺陷（位错、取代元素和氧空位）对稳定性和反应动力学的影响。这项研究获得的关键知识将推动未来储能和转换系统中新型钠离子存储陶瓷材料的发展。此外，在大学预科、本科和研究生阶段积极招收代表性不足的少数民族学生。该项目使学生能够在不同的国家实验室和共享的加州大学系统用户设施中接受先进的仪器培训，并在会议上展示他们的发现，从而扩大代表性不足的学生的参与并突出他们的研究。

NON-TECHNICAL DESCRIPTION: The demand for alternative energy sources has significantly increased in the past decade. Ceramics have revolutionized modern technologies such as electric vehicles, and more importantly renewable energy storage through the use of rechargeable electrochemical energy storage systems that couple chemical and electrical processes to convert the chemical energy to electric current. Sodium (Na) intercalation ceramics play a critical role in enabling possible use of rechargeable Na-ion batteries as the key large-scale energy storage systems. The high natural abundance and broad distribution of Na resources offer significant cost advantages. Yet Na ion batteries have not reached their full potential; therefore, it is imperative that high energy and power density materials are developed to further improve the technology. This project aims at discovering new high performance materials as well as exploring the interfacial science and defect engineering in ceramics. By taking a systematic approach using a suite of powerful analytical tools paired with first principles computational modeling, it is possible to identify the fundamental mechanisms in new ceramic materials for energy storage and conversion, in this case, sodium ion storage materials. Investigating and improving ceramic cathode materials for sodium ion batteries provides vital exposure to the next generation of research scientists through outreach activities for local underrepresented high school students with an interest in the materials science and engineering.TECHNICAL DETAILS: During the electrochemical process, structural changes due to first order and second order phase transformations that affect the system's electrochemical performance are noticeable in the voltage profile. In addition, subtle yet critical changes occur at the electrode-electrolyte interfaces, limiting the lifetime of any ceramic materials used for energy storage. This research is significantly improving the understanding of both these structural phase transformations and surface/interface modifications, and at the same time is exploring their effects on ion transport and charge transfer in sodium ion intercalation compounds. Various types of surface modification are being carried out including carbon coating, sol-gel coating, and atomic layer deposition coating on sodium intercalation ceramic materials. Advanced surface probe techniques are being applied to find the changes in surface/interface structure and chemistry in sodium electrochemical cells. The objectives of this work are to determine: 1) structural factors that promote enhanced sodium ion mobility; 2) interfacial effects on ion transport and charge transfer; and, 3) effects of defect (dislocations, substitutional elements, and oxygen vacancies) on stability and reaction kinetics. This study obtains key knowledge that will propel the development of new sodium ion storage ceramic materials for future energy storage and conversion systems. Furthermore, active recruitment of underrepresented minority students is carried out at precollegiate, undergraduate as well as graduate levels. The project enables students to receive advanced instrument training at various national laboratories and shared University of California system user facilities and present their findings at conferences, thereby broadening participation of underrepresented students and highlighting their research.