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

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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.