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.