Carbonization/oxidation-mediated synthesis of MOF-derived hollow nanocages of ZnO/N-doped carbon interwoven by carbon nanotubes for lithium-ion battery anodes†
Transition metal oxide (TMO)-based anode materials for Li-ion batteries (LIBs) have generally suffered from limitations of intrinsically severe pulverization upon lithiation and reduced electrical conductivity. To address these issues, an approach of generating hollow nanostructures of TMOs complexed with highly conductive species has been attempted. As a novel means to implement highly electrochemically active TMO-based hollow nanostructures, a pre-synthesized template of a metal organic framework, zeolitic imidazolate framework (ZIF-8), was sequentially treated with partial carbonization and oxidation processes, whereby a hollow, nanocage-like structure of ZnO was obtained while preserving the carbonaceous frame as the electroconductive matrix. Furthermore, through additional incorporation of carbon nanotubes (CNTs), hollow nanocages of ZnO/N-doped carbon were successfully interwoven to form a well-complexed three-dimensional network, imparting enhanced electrical conductivity and mechanical stability to the complexes. When the synthesized ternary nanocomposites of ZnO/N-doped carbon/CNTs were used as anodes of LIBs, enhanced electrochemical performance was achieved, with high specific capacity, excellent rate capability, and greatly extended cycling stability, which could be attributed to the facilitated Li-ion diffusivity and improved electrical conductivity. Therefore, it is highly expected that the proposed strategy could be extended as a general platform for realizing uniquely structured TMO-based electrode materials for high-performance energy storage systems.