This project addresses energy storage systems for the transportation and the intermittent supply of electricity generated by wind and solar power technologies. One potential solution for these applications is the use of sodium-ion batteries that utilizes widely available and domestic resources. Sodium ion batteries have similar functioning mechanisms as lithium ion batteries but cost less, as sodium is much more abundant than lithium. Currently, the performances of sodium ion batteries are mainly limited by the cathode electrode materials. Most of the existing cathode materials of sodium ion batteries suffer from low capacity and short cycle life. In addition, precious metals such as cobalt and nickel are typically used in these electrode materials, which increases the cost. This project aims to develop low cost and high performance novel cathode materials based on the oxides of one of the most abundant elements, manganese. The cathode materials are designed using strategies derived from fundamental science that allow the cathode to be charge-discharge cycled for hundreds of times with minimal performance degradation. For educational impacts, the project will advance knowledge in the fields of solid state chemistry and electrochemistry. The progress and new findings of the project will be included in undergraduate and graduate courses and disseminated to high school teachers and students through summer programs. The outcomes of the project will expedite the development and commercialization of sodium ion batteries, and therefore significantly improve the sustainability of energy storage technologies.
The stability of the crystal structure in cathode electrode materials in continuous electrochemical charge-discharge cycles is key to obtain long cycle life in sodium ion batteries. This project focuses on rational design of novel sodium manganese oxide cathode materials with layered structures. Novel strategies are used to stabilize their structure by doping selected elements into the manganese sites. The doping is expected to effectively delay or mitigate the phase transitions during the sodium intercalation and deintercalation processes, therefore allowing high capacity and long cycle life. The designed materials will be synthesized and electrochemically tested. Multiple advanced characterization methods such as in situ X-ray diffraction will be used to investigate the changes of the crystal structure of the materials during electrochemical cycling. By interpreting the results from synthesis, electrochemical tests, and structure characterizations, insights on the structural stability of the layered cathode materials will be revealed, the hypotheses will be validated, and the materials design strategies will be verified and further refined to guide the development of next generation high performance cathode electrode materials for sodium ion batteries.