Paper EH-ThM2
Real-Time TEM Observation of Electrochemistry and Failure in Battery Materials

Thursday, December 6, 2018, 8:20 am, Room Naupaka Salon 6-7

Electrodes in rechargeable batteries undergo complex electrochemically-driven phase transformations upon driving Li ions into their structure. Such phase transitions in turn affect the reversibility and stability of the battery. This presentation gives an overview of the PI’s research program on in-situ transmission electron microscopy (TEM) of ceramic battery materials. In-situ TEM has been shown to be a very powerful technique in shedding light to some of the mysteries in electrochemical performance of new materials. Various anode materials including SnO₂ and MnO₂ were subjected to lithiation process and the transport of Li ions was visualized within their atomic structure. For SnO₂ nanowires, it was observed that the Li ion transport results in local strain development preferably along (200) or (020) plans and [001] crystallographic directions. The lithiation behavior in the presence of twin boundary defects was completely different compared to pristine state with no twin boundary defect. We showed that twin boundaries in general provide a more accessible pathway for Li ion transport. Anisotropic plastic deformation was also observed along [010] directions of MnO₂ nanowires. Sb-based intermetallics which have been proved to be promising anode materials for Li-ion batteries, are also capable of storing of sodium ions. We investigated the microstructural changes and phase evolution of such intermetallic nanowires using in-situ TEM. These alloys also exhibit a new cubic alloying phase that form by intermixing of the ABAB atomic ordering in hexagonal lithiated phase due to Li inclusion in their lattices. Our results indicate that the reaction between these alloys and sodium proceeds through a different pathway during the first compared to the subsequent cycles.