Three-dimensional porous graphene-metal oxide composite microspheres: Preparation and application in Li-ion batteries

The use of new three-dimensional (3D) porous graphene-metal oxide composite microspheres as an anode material for Li-ion batteries (LIBs) is first introduced here. 3D graphene microspheres are aggregates of individual hollow graphene nanospheres composed of graphene sheets. Metal oxide nanocrystals are uniformly distributed over the graphene surface of the microspheres. The 3D porous graphene-SnO₂ microspheres are selected as the first target material for investigation because of their superior electrochemical properties. The 3D porous graphene-SnO₂ and graphene microspheres and bare SnO₂ powders deliver discharge capacities of 1, 009, 196, and 52 mAh·g^-1, respectively, after 500 cycles at a current density of 2 A·g^-1. The 3D porous graphene-SnO₂ microspheres exhibit uniquely low charge transfer resistances and high Li-ion diffusivities before and after cycling.