Three-Dimensional Fe2N@C Microspheres Grown on Reduced Graphite Oxide for Lithium-Ion Batteries and the Li Storage Mechanism

Nanostructured iron compounds as lithium-ionbattery anode material have attracted considerable attention with respect to improved electrochemical energy storage and excellent specific capacity, so lots of iron-based composites have been developed. Herein, a novel composite composed of three-dimensional Fe2N@C microspheres grown on reduced graphite oxide (denoted as Fe2N@C-RGO) has been synthesized through a simple and effective technique assisted by a hydrothermal and subsequent heating treatment process. As the anode material for lithium-ion batteries, the synthetic Fe2N@C-RGO displayed excellent Li+-ion storage performance with a considerable initial capacity of 847 mAh g(-1), a superior cycle stability (a specific discharge capacity of 760 mAhg(-1) remained after the 100th cycle), and an improved rate-capability performance compared with those of the pure Fe2N and Fe2N-RGO nanostructures. The good performance should be attributed to the existence of RGO layers that can facilitate to enhance the conductivity and shorten the lithium-ion diffusion path; in addition, the carbon layer on the surface of Fe2N can avert the structure decay caused by the volume change during the lithiation/delithiation process. Moreover, in situ X-ray absorption fine-structure analysis demonstrated that the excellent performance can be attributed to the lack of any obvious change in the coordination geometry of Fe2N@C-RGO during the charge/discharge processes.