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

Abstract

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 250cycles, the HCO/NGC composite powders with 11wt% NGC delivered a discharge capacity of 1030mAhg−1 at a current density of 1Ag−1. In addition, the composite powders delivered a discharge capacity of 738mAhg−1 even at a high current density of 10Ag−1.