Macroporous Fe 3 O 4 /Carbon Composite Microspheres with a Short Li + Diffusion Pathway for the Fast Charge/Discharge of Lithium Ion Batteries

Macroporous Fe 3 O 4 /carbon composite and core–shell Fe 3 O 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 3 O 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 3 O 4 /carbon composite shows distinct peaks at around 10 and 80 nm. An electrode prepared from the macroporous Fe 3 O 4 /carbon composite microspheres showed better cycling and rate performances than an electrode formed from core–shell Fe 3 O 4 @carbon composite microspheres. The initial discharge and charge capacities of the macroporous Fe 3 O 4 /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 .