Metal–organic framework-templated hollow Co₃O₄ nanosphere aggregate/N-doped graphitic carbon composite powders showing excellent lithium-ion storage performances

Hollow Co₃O₄ nanosphere aggregate/N-doped graphitic carbon (HCO/NGC) composite powders, exhibiting excellent Li-ion storage performances, were prepared by applying metal–organic frameworks (MOFs). Zeolitic imidazolate framework (ZIF)-67 cubes were reduced to produce Co/NGC composite powders. The Co/NGC composite powders were oxidized to produce cubic HCO/NGC composite powders, in which the hollow Co₃O₄ nanospheres were uniformly covered with a NGC layer. The Co nanocrystals transformed into hollow nanospheres during oxidation via the nanoscale Kirkendall diffusion process. The unique composite structure accommodates mechanical stress owing to the void spaces within the Co₃O₄ nanospheres; it also prevents structure collapse during cycling owing to the presence of the NGC matrix. Thus, the cubic hollow powders exhibited excellent electrochemical performances when used as an anode material in Li-ion batteries (LIBs). Following 250 cycles, the HCO/NGC composite powders with 11 wt% NGC delivered a discharge capacity of 1030 mA h g^{− 1} at a current density of 1 A g^{− 1}. In addition, the composite powders delivered a discharge capacity of 738 mA h g^{− 1} even at a high current density of 10 A g^{− 1}.