Macroporous Fe₃O₄/carbon composite microspheres with a short Li⁺ diffusion pathway for the fast charge/discharge of lithium ion batteries

Macroporous Fe₃O₄/carbon composite and core-shell Fe₃O₄@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 Fe₃O₄/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 Fe₃O₄/carbon composite shows distinct peaks at around 10 and 80 nm. An electrode prepared from the macroporous Fe₃O ₄/carbon composite microspheres showed better cycling and rate performances than an electrode formed from core-shell Fe₃O ₄@carbon composite microspheres. The initial discharge and charge capacities of the macroporous Fe₃O₄/carbon composite microsphere electrode were determined to be 1258 and 908 mA h g^-1 at 2 A g^-1, respectively, and the corresponding initial coulombic efficiency was 72 %. The composite microsphere electrode cycled 500 times at 5 A g^-1 showed a high discharge capacity of 733 mA h g^-1.