Surface Coating for High-Capacity Electrodes in Li-ion Batteries: in-situ TEM Characterization and First-Principles Modeling

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Rechargeable lithium ion batteries help to enable sustainable energy systems by storing electricity generated by intermittent renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. However, lithium ion batteries designed for high energy storage capacity suffer from rapid power capacity loss over repeated charge and discharge cycles. This project seeks to elucidate of the underlying mechanisms of capacity loss through microscopic investigation of the changes in battery electrode structure during charging and recharging using transmission electron microscopy (TEM), which enables visualization at the nanometer scale. The microscopic study will be complimented by mathematical modeling studies that seek to predict the observed behavior. The educational activities associated with this project focus on hands-on outreach activities for middle school students on battery technology, coordinated through the Women in Engineering program at Purdue University. The overall goal of this research is to investigate how metal oxide coatings on high-capacity, lithium ion battery electrodes affect charge capacity fade through in-situ transmission electron microcopy (TEM) experiments and first-principles modeling. Surface coatings can potentially mitigate the degradation of electrodes through regulation of the electrochemical process of lithiation and the remediation of deformation dynamics. However, the electro-chemo-mechanical behavior of the coating materials is poorly understood. To develop a fundamental understanding of these processes, the research plan has two major objectives. The first objective is to synthesize core-shell structures of metal oxide-coated nanowires to directly observe the lithiation reaction and the morphological evolution and phase transitions associated with it using real-time, in situ TEM. The second objective is to perform first-principles atomistic modeling to develop a complimentary fundamental understanding of the effects of lithium ion insertion and extraction on electronic structure, crystal lattice structure, and structural stability. Through these objectives, the proposed research will determine the thermodynamics of diffusive reactions and phase transitions, the kinetics of structural evolution, ionic transport, and interfacial reactions, as well as the mechanical properties of the lithiated phases in the coating materials. The knowledge gained from this work will facilitate the selection of coating materials for high-capacity lithium ion batteries, and advance fundamental understanding of the intrinsic mechanisms underlying the cyclic performance of Li-ion batteries.