MATERIALS SCIENCE AND ENGINEERING SEMINAR The Effect of Microstructure on the Performance of Li-Ion Porous Electrodes By: Ding-Wen Chung Master of Science Final Examination Advisor: Prof. R. E. Garcia ABSTRACT By combining X-ray tomography data and computer-generated porous electrodes, the impact of microstructure on the energy and power density of lithium-ion batteries is analyzed. Specifically, for commercial LiMn2O4 electrodes, results indicate that a broad particle size polydispersity of active material delivers up to two times higher energy density than monodisperse-sized particles for low discharge rates, and a monodisperse particle size distribution delivers the highest energy and power density for high discharge rates. The limits of traditionally used microstructural properties such as tortuosity, reactive area density, particle surface roughness, morphological anisotropy were tested against degree of particle size polydispersity thus enabling the identification of optimal porous architectures. The effects of critical battery processing parameters, such as layer compaction and carbon black were also rationalized in the context of electrode performance. While a monodisperse particle size distribution exhibits the lowest possible tortuosity and three times higher surface area per unit volume with respect to an electrode conformed of polydisperse particle size distribution, comparable performance can be achieved by polydisperse particle size distributions with degrees of polydispersity less than one fifth of the average particle size. The use of non-spherical particles raises the tortuosity by as much as three hundred percent, which considerably lowers the power performance. However, the use of favorably aligned particles can maximize power performance, particularly for high C-rate applications. Date: Tuesday, June 25, 2013 Time: 1:30 P.M. Place: ARMS 1021 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100