NSF Award
1800619
The increased use of sustainable but intermittent power sources (solar, wind, tidal, etc.) depends on the availability of robust energy storage capability. The wider adoption of electric vehicles also demands the development of efficient energy storage technology. Presently it is the lithium ion battery (LIB) that best satisfies these needs but with limitations, including energy capacity, performance, safety, and cost. In this regard, high capacity LIB anodes like silicon and tin dioxide can play an important role. However, these high capacity electrodes can undergo dramatic structural changes during battery charging/discharging and thus lose capacity rapidly. This project's goal is to address these limitations by the use of readily available materials (silicon and tin dioxide) in novel structural forms called asymmetric membranes. These membranes are designed to account for the volume changes during cycling while maintaining structural integrity. The asymmetric membranes can be fabricated using a scalable and low-cost method that has been successfully commercialized for water purification. For educational broader impacts, existing successful programs at Georgia Southern University (GSU) will be utilized to broaden the educational impact and provide research experiences for both undergraduate and graduate students. The PI will leverage existing resources at GSU to help broaden participation of underrepresented minorities and women in undergraduate research experiences that benefit the project. The PI will also collaborate with local chapters of The National Organization for the Professional Advancement of Black Chemists and Chemical Engineers (NOBCChE) and McNair Scholars at GSU to encourage participation of student researchers.<br/><br/>The major goal of this research program is to test the hypothesis that the electrochemical performance of high-capacity lithium ion battery (LIB) alloying anodes such as Si and SnO2 can be significantly enhanced using novel asymmetric membrane structures. Another goal is to investigate the physiochemical evolution of these asymmetric membrane electrodes during repeated charging/discharging processes. Commercial LIBs use relatively low-capacity graphite for anodes. In contrast, the theoretical capacities of alloying anodes such as Si and Sn for LIBs are several to ten folds higher. The drawback to using Si and Sn in anode construction is the roughly 300% volume change during the cycling process, which can lead to pulverization, unstable solid-electrolyte interphase, and rapid capacity loss. The PI will investigate whether using carbonized asymmetric membrane electrodes that contain silicon and tin dioxide can significantly increase LIB anode capacity while maintaining a long cycling life and an excellent rate performance. The material synthesis and membrane fabrication use proven scalable methods of self-assembling phase-inversion method and then roll to roll fabrication. In situ Raman spectroscopy and in situ powder X-ray diffractometry will be used to characterize the anodes during operation. The gained knowledge will enhance the fundamental understanding of the structural and electrochemical evolution of silicon and tin dioxide asymmetric membrane electrodes that experience large volume variation, thus potentially transforming the design of high capacity LIB electrodes.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
