Controllable synthesis and coating-thickness-dependent electrochemical properties of mesoporous carbon-coated α-Fe2O3 nanoparticles for lithium-ion batteries

Mesoporous carbon-coated iron oxide (α-Fe 2 O 3 @C) nanoparticles were hydrothermally synthesized by using α-Fe 2 O 3 nanospheres (ca. 50 nm) as the cores and resorcinol as the carbon source of the shells. The formation of the mesoporous carbon coatings was confirmed by means of SEM, TEM , FT-IR, TG, XPS and BET measurements. Moreover, the coating thickness was easily adjusted to be 4, 7 and 10 nm by changing the amount of resorcinol. When used as the anodes for lithium-ion batteries (LIBs), the α-Fe 2 O 3 @C nanoparticles exhibited significantly improved electrochemical properties as compared to pure α-Fe 2 O 3 nanoparticles. With the increase of the coating thickness, the α-Fe 2 O 3 @C electrodes presented an initial increase and subsequent decrease in their cycling stability and rate performance. Especially, the α-Fe 2 O 3 @C-7 nanoparticles displayed a high reversible capacity of 1223 mA h/g at 1 A/g, a good cycling stability retaining 1093 mA h/g at 1 A/g after 100 cycles as well as a remarkable rate performance of 570 mA h/g at 5 A/g. The quantitative kinetic analysis revealed that 58 % of the charge storage was contributed by the capacitive process at 0.5 mV/s. The well-defined core-shell structure and superior electrochemical performance of the α-Fe 2 O 3 @C-7 nanoparticles will make them a promising anode for LIBs.