Orientation-Dependent Intercalation Channels for Lithium and Sodium in Black Phosphorus.

摘要: Black phosphorus (BP) with unique 2D structure enables the intercalation of foreign elements or molecules, which makes BP directly relevant to high-capacity rechargeable batteries and also opens a promising strategy for tunable electronic transport superconductivity. However, underlying mechanism is not fully understood. Here, comparative investigation on electrochemically driven lithium sodium using in situ transmission electron microscopy presented. Despite same preferable channels along [100] (zigzag) direction, distinct anisotropic behaviors are observed, i.e., Li ions activate lateral [010] (armchair) direction form an overall uniform propagation, whereas Na diffusion limited zigzag cause columnar intercalation. First-principles calculations indicate that both energetically favorable, while Li/Na long armchair encounters increased energy barrier, but significantly larger insurmountable, accounts orientation-dependent channels. The evolution chemical states during phase transformations (from Lix P/Nax P Li3 P/Na3 P) identified by analytical diffraction energy-loss spectroscopy. findings elucidate atomistic mechanisms show potential implications other similar materials.