Three-dimensional carbon-coated ZnFe2O4 nanospheres/nitrogen-doped graphene aerogels as anode for lithium-ion batteries

Three-dimensional (3D) porous carbon-coated ZnFe2O4 nanospheres/N-doped graphene aerogels (ZnFe2O4@C/N-G) have been synthesized via a facile hydrothermal method. The obtained ZnFe2O4@C hierarchical nanospheres with a size distribution of 150-210 nm are uniformly encapsulated within the graphene aerogels matrix. The ZnFe2O4@C/N-G composites as anode materials for Li-ion batteries demonstrate a high initial discharge capacity of ~1176 mA h g−1 with an initial coulombic efficiency of ~71.1% at a rate of 100 mA g−1. Moreover, a significantly enhanced reversible capacity of 952 mA h g−1 is retained after 100 cycles. After being cycled at various rates for 100 cycles, the capacity can reincrease to 955 mA h g−1 when the specific current returns back to 100 mA g−1. The improved electrochemical performance is attributed to the unique architectures of the carbon layer (~2 to 4 nm) and 3D porous N-doped graphene aerogels.