▎ 摘　　要

In recent years, graphene-incorporated micro-/nanocomposites represent one of the hottest developing directions for the composite materials. However, a large number of active nanoparticles (NPs) are still in the unprotected state in most constructed graphene-containing designs, which will seriously impair the effects of the graphene additives. Here, a fully protected Fe3O4 -based micro-/nanocomposite (G/Fe3O4@C) is rationally developed by carbon-boxing the common graphene/Fe(3)O(4)microparticulates (G/Fe3O4). The processes and results of full protection are tracked in detail and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen absorption-desorption isotherms, as well as scanning and transition electron microscopy. When used as the anode for lithium-ion batteries, the fully protected G/Fe3O4@C exhibits the best lithium-storage properties in terms of the highest rate capabilities and the longest cycle life compared to the common G/Fe3O4 composites and commercial Fe3O4 products. These much improved properties are mainly attributed to its novel structural features including complete protection of active Fe3O4 nanoparticles by the surface carbon box, a robust conductive network composed of nitrogen-doped graphene nanosheets, ultra-small Fe3O4 NPs of 4-5 nm, abundant mesopores to accommodate the volume variation during cycling, and micrometer-sized secondary particles.