One-pot synthesis of uniform Fe3O4 nanocrystals encapsulated in interconnected carbon nanospheres for superior lithium storage capability

Uniform and small Fe3O4 nanocrystals (∼9 nm) encapsulated in interconnected carbon nanospheres (∼60 nm) for a high-rate Li-ion battery anode have been fabricated by a one-step hydrothermal process followed by annealing under Ar, which can be applied for the preparation of a number of metal oxide nanocrystals encapsulated in interconnected carbon nanospheres. The as-synthesized interconnected Fe3O4@C nanospheres displayed high performance as an anode material for Li-ion battery, such as high reversible lithium storage capacity (784 mA h/g at 1 C after 50 cycles), high Coulombic efficiency (∼99%), excellent cycling stability, and superior rate capability (568 mA h/g at 5 C and 379 mA h/g at 10 C) by virtue of their unique structure: the nanosized Fe3O4 nanocrystals encapsulated in interconnected conductive carbon nanospheres not only endow large quantity of accessible active sites for lithium ion insertion as well as good conductivity and short diffusion length for lithium ion transport but also can effectively circumvent the volume expansion/contraction associated with lithium insertion/extraction.