Melamine-assisted one-pot synthesis of hierarchical nitrogen-doped carbon@MoS2 nanowalled core–shell microspheres and their enhanced Li-storage performances†
Abstract
A facile and scalable one-pot approach has been developed to synthesize carbon@MoS2 core–shell microspheres by a hydrothermal method, which involves the fast formation of melamine–resorcinol–formaldehyde polymeric microspheres in situ, followed by direct growth of the MoS2 nanowalls on them. The results give unequivocal proof that melamine could be the key to forming the core–shell microspherical morphology, and the contents of MoS2 shells can be easily tuned by initial ratios of the precursors. After a simple heat treatment, the obtained carbon@MoS2 microspheres simultaneously integrate the nitrogen-doped carbon cores and the hierarchical shells which consist of few-layered MoS2 nanowalls with an expanded interlayer spacing. Their unique architectures are favourable for high electronic/ionic conductivity and accommodate volume strain during the electrochemical reaction of the MoS2 anodes in lithium-ion batteries. Thus, a very high reversibility capacity of 771 mA h g−1 at 100 mA g−1 after 100 cycles, and a rate capacity of 598 mA h g−1 at 2000 mA g−1 could be achieved for the carbon@MoS2 core–shell microspheres with the optimal composition. Furthermore, a thin carbon coating on the carbon@MoS2 microspheres could further increase the reversible capacity to 856 mA h g−1 after 100 cycles at 100 mA g−1. These encouraging results suggest that such a facile and efficient protocol can provide a new pathway to produce hierarchical core–shell microspheres which integrate the structural, morphological and compositional design rationales for advanced lithium-ion batteries.