EELS probing of lithium based 2-D battery compounds processed by liquid phase exfoliation. (December 2016) - Pokle, Anuj
Abstract: Two-dimensional lithiated nanosheets usually show excellent electrochemical performance due to an increase in surface area and shorter diffusion paths. However, processing techniques, such as shear mixing or liquid phase exfoliation could induce phase changes or knock out some of the structural lithium (Li) ions, what in turn might result in poor electrochemical performance. Here different lithiated layered compounds mainly LiCoO2, LiMn2 O4, and Li5 Ti4 O12 were chemically exfoliated and investigated using electron energy loss spectroscopy (EELS) for their Li-K edge. Further analyses were carried out, looking at the oxygen (O) K edge with their respective transition metal core loss peak (Mn, Co and Ti) which revealed changes in the Energy loss near edge structures (ELNES) when compared to the unlithiated compounds. STEM-EELS analyses confirmed uneven distribution of lithium within the lithiated layered materials. In this work, EELS was used for the first time to detect and to probe the chemical environment of the lithium in liquid phase exfoliated material. Graphical abstract: Highlights: Probing the presence of lithium and its chemical environment in liquid-phase exfoliated material using Electron Energy Loss Spectroscopy. Knock on damage to Li in TEM/STEM mode. Detection of lithium having beam control in STEM mode for spatial resolution and distribution. Charge transfer from lithium by analyzing the low and core loss spectra. Statistical analyses on Li content, carried out over flakes centrifuged at different speeds.