Diffusion induced concave Co₃O₄@CoFe₂O₄ hollow heterostructures for high performance lithium ion battery anode

A facile and effective approach to prepare Co₃O₄/CoFe₂O₄ hollow cubes with uniform size and complex interior architectures is proposed via annealing of metal-cyanide-bridged hybrid coordination polymers (HCPs). The synergistic effect of the hybrid metal oxides and the rational design of the architecture endow these heterostructures with good lithium storage property and charge carrier transfer kinetics. In the hybrid materials, CoFe₂O₄ offers high theoretical capacity and Co₃O₄ provides stability at high current densities, leading to the significant enhancement in lithium storage properties comparing to the pure CoFe₂O₄. For example, Co₃O₄/CoFe₂O₄ heterostructures annealed at 800 °C exhibit a high capacity of 511 mA h g^-1 at a current density of 8.0 A g^-1 and a reversible capacity of 515 mA h g^-1 during the 500th cycle at a current density of 5.0 A g^-1.