N-doped graphitized carbon-coated Fe2O3 nanoparticles in highly graphitized carbon hollow fibers for advanced lithium-ion batteries anodes

Ferric oxide (Fe2O3) has become one of the most competitive candidates for the next-generation lithium-ion batteries anode materials due to its high theoretical reversible specific capacity (Cs, 1007 mAh g- 1) and low price. However, the rapid capacity fading and poor rate performance deriving from drastic volume expansion (-200 %), low Coulombic efficiency (CE), and poor electrical conductivity limit its application in LIBs. Herein, a novel encapsulation structure of Fe2O3 nanoparticles has been developed. Fe2O3 nanoparticles inlaid in the shells of hollow highly graphitized carbon fibers are coated by N-doped graphitized carbon (GF-FeO@NGC) by a catalytic graphitization, oxidation route of Fe-based catalyst. The GF-FeO@NGC electrode shows the first specific discharge/charge capacities of 1355/974 mAh g- 1 with high initial Coulombic efficiency (ICE) of 72.0%, and excellent reversibility of lithiation/delithiation reaction. After 200 cycles at 0.1 A g- 1, the GF-FeO@NGC electrode keeps a high reversible Cs of 918 mAh g- 1 (retention of 94.3%) with a CE of 99.6%. It is noticeable that the GF-FeO@NGC electrode has good rate performance and robust cycling stability at high current density. After 300 cycles at 2 A g- 1, the Cs retention is up to 97.1% with a CE of 99.7%. These are far superior to those of the GFFeO (without NGC coating) and the most reported Fe2O3-based electrode materials. The mechanism behind these phenomena are studied.

Automated summary

A novel encapsulation structure of Fe2O3 nanoparticles coated with N-doped graphitized carbon has been developed to improve the electrochemical performance. The GF-FeO@NGC electrode exhibits high reversible specific capacity, good rate performance, and robust cycling stability.