2016 — 2021 |
Melot, Brent |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Career: Understanding the Influence of the Framework On Alkali Ion Diffusion in Polyanionic Intercalcation Electrodes @ University of Southern California
Non-Technical Abstract From cellular phones to portable computers, many major technological advances in recent years have relied on the ability to store massive amounts of energy within extremely small batteries. These batteries operate by reversibly inserting and removing Li-ions from electrochemically active host materials. The goal of this work, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, is to build a deeper understanding of what happens at the atomic level of these hosts as Li-ions move through their crystal structures. This fundamental knowledge is crucial for increasing the rate at which batteries can be (dis)charged as well as prolonging their operational lifetime. In parallel, this work seeks to use this understanding to identify new Earth-abundant electrode materials for Na-ion batteries in order to reduce the cost of producing large-scale energy storage systems for electric vehicles and the grid. This project also focuses on encouraging middle school students in the Native American communities located within the Los Angeles area to increase their participation in STEM disciplines. Hands-on teaching demonstrations and experiments are used to demystify the often puzzling world of electricity and energy sciences to engage students in science from an early age.
Technical Abstract Polyanionic transition metal compounds (like phosphates, sulfates, and silicates) are of critical importance to energy storage because they do not release oxygen on decomposition, which can exacerbate thermal runaway during cell failure, and are therefore considerably safer than oxide-based electrodes. While a large body of work has been dedicated to optimizing the electrochemical performance of these materials, there is a fundamental lack of understanding about the mechanism for Li-ion transport in these materials. Unlike state-of-the-art oxides, which effectively exhibit isotropic changes in their oxygen sublattice, polyanionic electrodes respond to the removal or insertion of Li through cooperative rotations of their rigid oxoanionic subunits. This work is focused on investigating the mechanism of alkali-ion diffusion in polyanionic intercalation hosts using high-resolution X-ray and neutron diffraction techniques in order to characterize how the framework of these materials changes on charge and discharge. Understanding how these densely packed solids facilitate the motion of positively charged ions through their lattices is critical for accelerating the design of next-generation materials for batteries that can operate based on the transport of larger ions like Na.
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0.915 |
2019 — 2022 |
Thompson, Mark (co-PI) [⬀] Thompson, Mark (co-PI) [⬀] Melot, Brent Djurovich, Peter |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Design and Preparation of Organic-Metal Halide Hybrids Exhibiting Charge Transfer @ University of Southern California
PART 1: NON-TECHNICAL SUMMARY In the last ten years, solar cells based on hybrid materials that contain organic and inorganic components have exhibited rapidly improving performance that has now reached levels competitive with commercial silicon panels. Through this project, which is supported by the Solid State and Materials Chemistry program at NSF, the research team at the University of Southern California develops a deeper understanding of why these materials perform so exceptionally well and investigates strategies to push the performance of these hybrid materials even higher in the future. The work is highly interdisciplinary, combining efforts in organic synthesis, computational chemistry, and physical property measurements to examine how light interacts with these complex materials. The project also engages undergraduates from the nearby Cerritos Community College (which is 54% Latino, 8% African American) and Native American High School students in the research.
PART 2: TECHNICAL SUMMARY This project, which is supported by the Solid State and Materials Chemistry program at NSF, deepens our fundamental understanding of how organic molecules in their excited state interact within periodic inorganic structures. In previous studies the organic component has been predominantly structural in nature, not actively participating in the valence or conduction bands. In this project the research team at the University of Southern California focuses on materials where the organic component is an active optical or electronic element, by making it a major contributor to the valance and/or conduction bands of the hybrid solid. The principle investigators develop new material design principles to promote enhanced charge transport of photoexcited carriers through the solid state. In the process, new understanding is achieved about how to align the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) of organic dyes with the conduction or valence bands of the extended framework. The materials that are developed during this study act as model systems to investigate how localized excitons on the organic molecules can be transferred into the far more delocalized bands of the metal halide region of the crystal. The systematic investigation involves a combination of materials design, synthesis, Density Functional Theory calculations, and physical property measurement to answer fundamental questions about how the organic and inorganic components interact within the crystal structure. Additionally, the project engages undergraduates from the nearby Cerritos Community College (which is 54% Latino, 8% African American) and Native American High School students in the research.
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.
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0.915 |