Porous ZnO/Co3O4/N-doped carbon nanocages synthesized via pyrolysis of complex metal-organic framework (MOF) hybrids as an advanced lithium-ion battery anode.

Metal oxides have a large storage capacity when employed as anode materials for lithium-ion batteries (LIBs). However, they often suffer from poor capacity retention due to their low electrical conductivity and huge volume variation during the charge-discharge process. To overcome these limitations, fabrication of metal oxides/carbon hybrids with hollow structures can be expected to further improve their electrochemical properties. Herein, ZnO-Co3O4 nanocomposites embedded in N-doped carbon (ZnO-Co3O4@N-C) nanocages with hollow dodecahedral shapes have been prepared successfully by the simple carbonizing and oxidizing of metal-organic frameworks (MOFs). Benefiting from the advantages of the structural features, i.e. the conductive N-doped carbon coating, the porous structure of the nanocages and the synergistic effects of different components, the as-prepared ZnO-Co3O4@N-C not only avoids particle aggregation and nanostructure cracking but also facilitates the transport of ions and electrons. As a result, the resultant ZnO-Co3O4@N-C shows a discharge capacity of 2373 mAh g-1 at the first cycle and exhibits a retention capacity of 1305 mAh g-1 even after 300 cycles at 0.1 A g-1. In addition, a reversible capacity of 948 mAh g-1 is obtained at a current density of 2 A g-1, which delivers an excellent high-rate cycle ability.