- Sooyeon Hwang, Brookhaven National Laboratory, Upton, New York
Electrode materials for lithium-ion batteries have been extensively explored for the development of lithium-ion batteries since physical and chemical properties of electrode materials govern the electrochemical properties of whole cells. Advanced transmission electron microscopy (TEM) techniques, providing tremendous information of materials’ morphology, microstructure, and chemical properties at nanoscales, have been playing an essential role in the characterization of electrode materials. With a combination of a number of TEM based techniques, including in situ TEM, electron diffraction, and electron energy-loss spectroscopy, structural evolution occurring electrode materials and their possible impact have been investigated. The speaker will discuss research involving the nascent structural degradation and thermal stability of lithium transition metal oxides after electrochemical tests. Incipient phase transformations were locally observed at the surface. In situ TEM heating experiments demonstrated that the local structural evolution could result in poor thermal stability of cathode materials, which may result in thermal runaway of whole batteries. The speaker will also discuss structural evolution of tin disulfides, promising anode materials, with regard to real-time TEM observation results during lithiation. It was demonstrated that the two-dimensional structure of tin disulfides allows lithium intercalation at first and that further lithium insertion changes the reaction to disordering, conversion, and alloying.