Delicate ternary heterostructures achieved by hierarchical co-assembly of Ag and Fe3O4 nanoparticles on MoS2 nanosheets: morphological and compositional synergy in reversible lithium storage

摘要

Nanostructured transition metal oxides and dichalcogenides have recently emerged as promising anode candidates for lithium-ion batteries due to their extraordinarily high theoretical capacities. Unfortunately, these nanomaterials still face two problems that are detrimental to their ultimate electrochemical performances. First, the morphological deficiency, imposed by their strong tendency to aggregate, inevitably causes a frustrating loss in reversible capacities. Second, the compositional deficiency, resulting from their inherently low conductivity, further hastens the electrolyte degradation leading to awful cyclability. Herein we propose a facile strategy for the hierarchical co-assembly of Ag and Fe3O4 nanoparticles (NPs) on MoS2 nanosheets, aiming to address the morphological and compositional deficiencies simultaneously. The three building blocks, together, act as an appealing trio: (1) the large, elastic and flexible MoS2 nanosheets serve as an ideal substrate to prevent NP aggregation and accommodate the strains during repeated lithation/delithation; (2) the small Fe3O4 NPs contribute superior capacities and rate capabilities by ensuring short Li+ ion diffusion pathways; (3) the highly conductive Ag NPs allow for efficient charge transport. As such, prominent morphological and compositional synergy is emphasized by superior reversible capacities and rate capabilities, ranking our Ag/Fe3O4-MoS2 ternary heterostructures as high-performance anode materials.