Macroporous Fe_3O_4/Carbon Composite Microspheres with a Short Li ~+ Diffusion Pathway for the Fast Charge/Discharge of Lithium Ion Batteries

摘要

Macroporous Fe_3O_4/carbon composite and coreshell Fe_3O_4@carbon composite microspheres have been prepared by means of one-pot spray pyrolysis. The addition of polystyrene (PS) nanobeads to a spray solution containing an iron salt and poly(vinylpyrrolidone) (PVP) led to macroporous Fe_3O_4/carbon composite microspheres, the carbon and iron components of which are uniformly distributed over the entire composite microsphere. The pore-size distribution curve for the macroporous Fe_3O_4/carbon composite shows distinct peaks at around 10 and 80 nm. An electrode prepared from the macroporous Fe_3O_4/carbon composite microspheres showed better cycling and rate performances than an electrode formed from core-shell Fe_3O_4@carbon composite microspheres. The initial discharge and charge capacities of the macroporous Fe_3O_4/carbon composite microsphere electrode were determined to be 1258 and 908 mAhg~(-1) at 2 Ag~(-1), respectively, and the corresponding initial coulombic efficiency was 72%. The composite microsphere electrode cycled 500 times at 5 Ag~(-1) showed a high discharge capacity of 733 mAhg~(-1).