β‑Sn Nanorods with Active (001) Tip Induced LiF-Rich SEI Layer for Stable Anode Material in Lithium Ion Battery

β-Sn nanorod (NR) with (200) facets and (001) tip is a potential anode material in lithium ion battery (LIB) due to its good cycle stability that can retain ∼600 and 550 mA h g–1 after 100 cycles using 0.2 C for high and low aspect ratios, respectively. The high stability compared to that of spherical nanoparticles can be attributed to the combination of the nanorod morphology that buffers large volumetric change, and the LiF-rich F-containing surface electrolyte interface (SEI) layer that allows for a stable SEI layer and a good ionic and electronic conductivity. The lower SEI resistivity and high Li+ diffusivity of low aspect ratio β-Sn NRs resulted in a better cyclability compared to high aspect ratio β-Sn NRs. These can be attributed to the higher specific surface area of highly reactive (001) surface, i.e., the tip of the rod, that produces a LiF-rich F-containing SEI layer of the lower aspect ratio compared to that of the higher aspect ratio β-Sn NRs.