Quadrangular-CNT-Fe3O4-C composite based on quadrilateral carbon nanotubes as anode materials for high performance lithium-ion batteries

A q-CNT-Fe3O4-C composite was synthesized via the homogeneous precipitation of FeOOH nanoparticles on quadrangular carbon nanotubes (q-CNT) substrates. The q-CNT multi-walled carbon nanotube featured one closed end and an open end with a quadrilateral cross section, and the nanotubes were prepared by using co-carbonization method. The FeOOH nanoparticles were encapsulated by amorphous carbon via a hydrothermal treatment and high-temperature calcination of glucose. TEM showed that diameter of the q-CNT was 100 nm and the tube thickness was 20 nm. The outer wall of the q-CNT was attached to Fe3O4 with sizes ranging from 80 to 100 nm via a layer of an amorphous carbon coating. It delivered a specific capacity of 1031.5 mAh g−1 after 100 cycles at a current density of 200 mA g−1. After 60 cycles, it showed a high specific capacity of 485.6 mAh g−1 even at 2000 mA g−1. CV and EIS results further suggested that the q-CNT-Fe3O4-C composite exhibited lithium ion uptake/release reversibility and a rapid high current charge/discharge capability. The excellent rate performances of the q-CNT-Fe3O4-C composite can be attributed to the superior electronic transport properties of the quadrilateral CNT with one open end and the synergistic effects of the hybrid components.