Chestnut-Like TiO₂@α-Fe₂O₃ Core–Shell Nanostructures with Abundant Interfaces for Efficient and Ultralong Life Lithium-Ion Storage

Transition metal oxides caused much attention owing to the scientific interests and potential applications in energy storage systems. In this study, a free-standing three-dimensional (3D) chestnut-like TiO₂@α-Fe₂O₃ core–shell nanostructure (TFN) is rationally synthesized and utilized as a carbon-free electrode for lithium-ion batteries (LIBs). Two new interfaces between anatase TiO₂ and α-Fe₂O₃ are observed and supposed to provide synergistic effect. The TiO₂ microsphere framework significantly improves the mechanical stability, while the α-Fe₂O₃ provides large capacity. The abundant boundary structures offer the possibility for interfacial lithium storage and electron transport. The as-prepared TFN delivers a high capacity of 820 mAh g^–1 even after 1000 continuous cycles with a Coulombic efficiency of ca. 99% at a current of 500 mA g^–1, which is better than the works reported previously. A thin gel-like SEI (solid electrolyte interphase) film and Fe⁰ phase yielded during charge/discharge cycling have been confirmed which makes it possible to alleviate the volumetric change and enhance the electronic conductivity. This confirmation is helpful for understanding the mechanism of lithium-ion storage in α-Fe₂O₃-based materials. The as-prepared free-standing TFN with excellent stability and high capacity can be an appropriate candidate for carbon-free anode material in LIBs.