UChicago PME Materials Seminar Series - Yiyang Li

Energy storage and semiconductor microelectronics are two critical strategic technologies for the United States. In this talk, I will present our recent research on the kinetics of ion transport within materials for batteries and microelectronics. In microelectronics, metal oxides fabricated using low-temperature processes are widely used in microelectronic devices including resistive memory, thin-film transistors, and ferroelectrics. Solid oxygen diffusion within these metal oxides play critical roles in the functionality and reliability of such devices. For materials used in resistive memory, we show that oxygen diffusion kinetics are not governed by ideal Fickian diffusion but are instead governed by nonideal thermodynamic interactions including phase separation and spinodal decomposition. This phase separation not only enables information retention for over 10 years under typical computing environments but can also be used to engineer nonvolatile memory under extreme temperatures exceeding 500C. Next, I will present our efforts to study lithium transport in battery materials using the microelectrode array, a technique borrowed from the field of neuroscience. By measuring lithium diffusion and reaction rates in individual particles, we show that particle cracking, which was long believed to be detrimental, is essential for the charge and discharge of battery particles for typical automotive applications. Moreover, attempts to eliminate cracks would substantially hinder fast charge and discharge. Such studies show the importance of ion transport in current and future technologies for energy, microelectronics, and beyond.