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.