Fe3O4-decorated graphene balls were prepared by a spray pyrolysis process. Analysis by Raman spectroscopy and X-ray photoelectron spectroscopy indicated that the spray pyrolysis at 800 °C resulted in the complete reduction of graphene oxide sheets containing oxygen functional groups into graphene sheets, leading to the formation of Fe3O4-decorated graphene balls. The graphene content in the composite ball was 27 wt%. The Brunauer-Emmett-Teller surface area of the Fe3O4-decorated graphene balls was as high as 130 m2 g-1. The initial discharge and charge capacities of the Fe3O4-decorated graphene balls at a high current density of 7 A g-1 were 1210 and 843 mAh g-1, respectively, and the discharge capacity was as high as 690 mAh g-1 even after 1000 cycles. The stable reversible discharge capacities of the Fe3O4-decorated graphene balls decreased from 1040 to 540 mAh g-1 with the increase in current density from 1 to 30 A g-1. The Fe3O4-decorated graphene balls with a uniform distribution of ultrafine Fe3O4 nanocrystals below 15 nm showed superior electrochemical properties as anode materials for lithium ion batteries. The overall structure of the Fe3O4-decorated graphene balls was maintained even after long-term cycling.
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