Stable Lithium Storage in Nitrogen-Doped Carbon-Coated Ferric Oxide Yolk-Shell Nanospindles with Preserved Hollow Space.

Iron oxide (Fe O ) is a promising anode material for next-generation high-energy lithium-ion batteries owing to its high theoretical specific capacity, but it suffers from unstable electrochemistry, as represented by a significant volume variation upon (de)lithiation and unstable solid-electrolyte interface. To target these issues, a double-coating synthetic route has been developed to prepare a yolk-shell-structured γ-Fe O /nitrogen-doped carbon composite, in which spindle-like γ-Fe O cores are encapsulated in the highly conductive carbon shell. Through precisely controlling the void space between the γ-Fe O core and the carbon shell, volume variation in γ-Fe O during (de)lithiation is well accommodated, while the composite maintains an intact and relatively dense structure, which stabilizes the solid-electrolyte interface and is beneficial for improving the practical energy density of the material. With a stabilized (de)lithiation electrochemistry and a synergistic storage effect between the two active components, the composite enables excellent lithium storage performance, in terms of reversible capacity, cycling ability, and rate capability.