Enhanced rate capability and cycling stability of core/shell structured CoFe2O4/onion-like C nanocapsules for lithium-ion battery anodes

In this work, core/shell structured CoFe2O4/onion-like C nanocapsules have been successfully fabricated by the arc discharge method and air-annealing process and confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The core/shell structure effectively withstands the volume change of CoFe2O4 nanoparticles during the cycling process. Moreover, the onion-like C shells reduce the charge transfer resistance and facilitate electron and ion transport throughout the electrode. As a result, CoFe2O4/onion-like C nanocapsules exhibit excellent performance as a potential anode material for lithium ion batteries and deliver a reversible capacity of 914.2 mA h g−1 at 0.1C, even after 500 cycles and recover its original capacity when the rate returns from 4C to the initial 0.1C after 120 cycles.