High-index faceted nickel ferrite nanocrystals encapsulated by graphene with high performance for lithium-ion batteries

Uniform octahedral nickel ferrite nanocrystals wrapped by graphene (GNFO) have been synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis techniques, which reveal that the NiFe2O4 nanocrystals are enclosed by high index (111) facets and encapsulated by reduced graphene oxide sheets. When applied as anode electrodes for lithium ion batteries, GNFO nanocomposites present excellent electrochemical performances. The electrode maintains 1275 mAh g−1 after 30 cycles at 0.1 A g−1 and a reversible capacity up to 937 mAh g−1 after 250 cycles at 1 A g−1. A prominent rate capability is also obtained and the specific capacity remains 312 mAh g−1 at 10.0 A g−1. The superior electrochemical properties could benefit from open surface structure of octahedral NiFe2O4 and synergistic effect between graphene and NiFe2O4, which shows promising applications in lithium-ion storage devices.