Nanoisland-like MoO₂ Embedded in N-Doped Carbon via Mo–N Bonds for Li-Ion Storage

Supramolecular precursors exhibit unique superiority in preparing functional nanocomposites comprised of ultrasmall active nanoparticles uniformly embedded in carbon. By virtue of the self-assembly of supramolecule MoO42––polydopamine (Mo-PDA) on the surface of sulfonated polystyrene microspheres, hierarchical hollow MoO2/nitrogen-doped carbon (H-MoO2/NC) microspheres, which are assembled from ultrathin nanosheets comprising of ultrasmall nanoisland-like MoO2 embedded in nitrogen-doped carbon, are obtained. During the preparation of H-MoO2/NC, the confining effect of the surrounding carbon effectively inhibits the growth of MoO2 nanoparticles and results in the formation of ultrasmall nanoisland-like MoO2. In addition, the nanoisland-like MoO2 is strongly embedded into nitrogen-doped carbon as indicated by the presence of strong Mo–N bond. The strong coupling between MoO2 nanocrystallites and nitrogen-doped carbon results in an enhanced synergistic effect for the electrochemical Li-ion storage. As a result, H-MoO2/NC manifests a high capacity and good long-term stability (1191 mAh g–1 in the 100th cycle at 0.2 C) as well as excellent rate behavior (a capacity of 697 mAh g–1 at 20 C).