Construction of Co3O4@TiO2 heterogeneous mesoporous hollow nanocage-in-nanocage from metal-organic frameworks with enhanced lithium storage properties

Co3O4@TiO2 heterogeneous mesoporous hollow nanocage-in-nanocage hybrid was constructed through coating Zeolitic imidazolate framework-67 with hydrous titania followed by the oxidation and crystallization treatment. Co3O4 nanocrystalline-assembled mesoporous hollow nanocage was encapsulated within ultrafine TiO2 nanocrystalline-assembled mesoporous hollow nanocage. The sizes of Co3O4 and TiO2 nanocages were around 600 and 800 nm, respectively. The BET surface area was 142 m2 g−1, and the total pore volume was 0.55 ml g−1. As anode materials for lithium ion batteries, Co3O4@TiO2 exhibited high reversible capacity, outstanding cycling performance and superior rate capability. At the 200th cycle, the discharge capacity reached 787.5 mAh g−1 with coulombic efficiency of 98.3% and capacity retention ratio of 84.8% (compared with the 2nd cycle) at a current density of 100 mA g−1. The average discharge capacity over 200 cycles was 839.5 mAh g−1. The superior Li-storage performance was ascribed to the nanocrystalline-assembled mesoporous hollow nanocage structure of Co3O4 and TiO2 as well as the unique nanocage-in-nanocage structure that gave full play to the good structural stability of TiO2 and high specific capacity of Co3O4. The material structure and synthesis strategy presented here offer a new pathway to develop high-performance nanocomposite of transition metal oxides for energy storage device applications. [Display omitted] •Co3O4@TiO2 heterogeneous mesoporous hollow nanocage-in-nanocage.•Unique mesoporous structure with large specific surface area and high porosity.•High reversible capacity, outstanding cycling performance and rate capability.