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.