Yoojin Ahn
Advisor: Dr. Meilin Liu

will propose a doctoral thesis entitled,

Development of niobium-based oxide anode materials with the Wadsley-Roth shear structure for high-power Li-ion batteries 

On

Friday, July 25 at 10:00 a.m. (EDT)
LOVE Room 183 
and
Virtually via MS Teams 
https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZDA5YzkwNDgtZmY4…

Meeting ID: 265 885 858 259
Passcode: wg36aL2Z


Committee
Dr. Meilin Liu –  School of Materials Science and Engineering (advisor)
Dr. Matthew McDowell – School of Materials Science and Engineering
Dr. Hamid Garmestani – School of Materials Science and Engineering 
Dr. Preet Singh – School of Materials Science and Engineering 
Dr. Angus Wilkinson – School of Chemistry and Biochemistry

Abstract
Li-ion batteries (LIBs) are among the most promising energy storage systems for portable devices and robotics due to their high energy density, stability, and safety. However, commercial LIBs typically use graphite anodes, which suffer from low volumetric energy density and limited fast-charging capability. A promising strategy to address these limitations is to replace graphite with metal oxide-based anodes, which offer higher volumetric capacity and high-rate capability. In particular, niobium-based oxides have attracted attention for fast-charging applications owing to their unique structural and electrochemical properties. This research proposal aims to optimize, characterize, and investigate the mechanisms of niobium-based oxide anode materials for LIBs. The first strategy is to develop high-capacity, stable niobium oxide anodes via defect engineering. Specifically, a metastable phase of Nb2O5, known as M-Nb2O5, which exhibits promising electrochemical properties, will be integrated into the stable H-Nb2O5 structure. M-Nb2O5 typically forms during the phase transition from orthorhombic Bronze T-Nb2O5 to monoclinic Wadsley-Roth shear H-Nb2O5, but its metastable nature has limited detailed studies. By forming a mixed H/M-phase Nb2O5, M-Nb2O5 can act as structural defects that enhance ion transport and improve electrochemical performance. The second strategy is to tune the Wadsley-Roth shear structure of niobium oxides through an entropy-tuning strategy. Entropy engineering, achieved by integrating five different cations, can stabilize the complex oxide phases and enhance their intrinsic properties. The synergistic effects of entropy tuning in niobium-based oxide are expected to exhibit improved structural stability and electrochemical performance under high-rate cycling conditions. The findings from this work will contribute to the development of next-generation fast-charging LIBs by advancing fundamental understanding and design strategies for high-performance niobium-based oxide anodes.