Synthesis and high-rate capability of quadrangular carbon nanotubes with one open end as anode materials for lithium-ion batteries

Novel carbon nanotubes (CNTs) were prepared on a large-scale. Their morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman measurements. It was found that the prepared CNTs possess a quadrangular cross section, as well as one open end and "herringbone"-like walls, so these novel CNTs were named q-CNTs. The unique morphology of q-CNTs implies broad potential applications in many fields, including drug delivery, conductive and high-strength composites, field emission displays and radiation sources, hydrogen storage media, and supercapacitors. When used as the anode materials for lithium-ion batteries, q-CNTs exhibit excellent high-rate performance (a high-reversible capacity of 181 mAh g−1 at the current density of 1000 mA g−1 (ca. 3 C)), which is much higher than that of the common multi-wall carbon nanotubes. This high-rate performance should be attributed to the unique nanostructure of q-CNTs, which results in a high diffusion coefficient for lithium ions in the q-CNTs.