DCMPMS Seminars

Oxides For Energy Storage and Energy-Efficient Devices – PART - II

by Dr. Naga Phani Aetukuri (IBM Almaden Research Center, Department of Materials Science and Engineering, Stanford University, CA)

Thursday, January 29, 2015 from to (Asia/Kolkata)
at AG80
Description
Metal oxides are a remarkable class of compounds that exhibit almost every known condensed matter phenomenon such as ferroelectricity, ferromagnetism, anti-ferromagnetism, high-Tc superconductivity and metal-insulator transitions. Furthermore, Li-intercalating metal oxides such as LiCO2 and LiFePO4 are used as cathode materials in Li-ion batteries, which have led to the widespread adoption of portable electronics and to the development of electric automobiles. In this talk, we will present our work on two distinct oxide systems – Li2O2 and VO2 – with applications in energy storage and low power electronic devices, respectively.

First, we will discuss the formation and morphological evolution of Li2O2 in the context of Li-O2 batteries, where Li2O2 is the battery’s discharge product. During the battery discharge, electrochemical deposition of Li2O2 causes electrode passivation because Li2O2 is an electronic insulator. This limits the maximum deposited thickness of Li2O2 and results in poor battery capacity. In this work, we show that activating an electrochemical solution-mediated pathway favors the deposition of large Li2O2 particles. Consequently, there is manifold increase in the battery’s discharge capacity.  We discuss the design rules for selecting electrolyte solvents that favor this alternate pathway and the implications of this research for metal-air batteries.

 Next, we will discuss our work on VO2-based heterostructures and devices. VO2 is an archetypal correlated electron system that exhibits a near room temperature metal-insulator transition (MIT) with a concomitant structural phase transition. In this second part of our presentation, we will discuss the control of MIT in liquid-electrolytegated VO2 devices and epitaxially-strained single-crystalline VO2 films.  We comment on the role of oxygen vacancies in inducing the MIT in electrolyte-gated devices. And, we show that the MIT in VO2 can be deterministically controlled by tuning the V 3d orbital configuration. We discuss possible device strategies that exploit MIT in VO2 and related materials.