Heterogeneous Double-Shelled Constructed Fe3O4 Yolk–Shell Magnetite Nanoboxes with Superior Lithium Storage Performances

Among the numerous candidate materials for lithium ion batteries, ferroferric oxide (Fe3O4) has been extensively concerned as a prospective anode material because of its high theoretical specific capacity, abundant resources, low cost, and nontoxicity. Here, we designed and fabricated a unique yolk–shell construction by generating heterogeneous double-shelled SnO2 and nitrogen-doped carbon on Fe3O4 yolk (denoted as Fe3O4@SnO2@C–N nanoboxes). The yolk–shell structured Fe3O4@SnO2@C–N nanoboxes have the adjustable void space, which permits the free expansion of Fe3O4 yolks without breaking the double shells during the lithiation/delithiation processes, avoiding the structural pulverization. Moreover, the heterogeneous double-shelled SnO2@C–N can meaningfully improve the electronic conductivity and enhance the lithium storage performance. Two metal oxides also show the specific synergistic effect, promoting the electrochemistry reaction. As a result, this yolk–shell structured Fe3O4@SnO2@C–N exhibits high spe...