Doping Graphene into Monodispersed Fe3O4 Microspheres with Droplet Microfluidics for Enhanced Electrochemical Performance in Lithium-Ion Batteries

Graphene-doped Fe3O4 monodispersed microspheres are fabricated utilizing a droplet microfluidic technology. The electrochemical performance of the Fe3O4 microspheres as anode material for Li-ion batteries is enhanced by doping trace graphene in the droplet reactor. The discharge capacity remains 550 mAh/g at 0.1 C after 190 cycles, which is 2 times higher than that of the graphene doped Fe3O4 samples prepared by the traditional precipitation method, and 5 times higher than that of pure Fe3O4 after 100 cycles. The uniform droplet reactor in form of a droplet microfluidic chip might provide a homogeneous microscopic condition for in-situ electrostatic coassembly of the positive-charged Fe colloids and the negativecharged graphene oxide sheets to shape a homogeneous solid framework, resulting in homogeneously doping trace graphene into the Fe3O4 microspheres.