Chestnut-Like\nTiO₂@α-Fe₂O₃ Core–Shell\nNanostructures with Abundant Interfaces\nfor Efficient and Ultralong Life Lithium-Ion Storage

Abstract

Transition\nmetal oxides caused much attention owing to the scientific\ninterests and potential applications in energy storage systems. In\nthis study, a free-standing three-dimensional (3D) chestnut-like TiO₂@α-Fe₂O₃ core–shell nanostructure\n(TFN) is rationally synthesized and utilized as a carbon-free electrode\nfor lithium-ion batteries (LIBs). Two new interfaces between anatase\nTiO₂ and α-Fe₂O₃ are observed\nand supposed to provide synergistic effect. The TiO₂ microsphere\nframework significantly improves the mechanical stability, while the\nα-Fe₂O₃ provides large capacity. The abundant\nboundary structures offer the possibility for interfacial lithium\nstorage and electron transport. The as-prepared TFN delivers a high\ncapacity of 820 mAh g^–1 even after 1000 continuous\ncycles with a Coulombic efficiency of ca. 99% at a current of 500\nmA g^–1, which is better than the works reported\npreviously. A thin gel-like SEI (solid electrolyte interphase) film\nand Fe⁰ phase yielded during charge/discharge cycling have\nbeen confirmed which makes it possible to alleviate the volumetric\nchange and enhance the electronic conductivity. This confirmation\nis helpful for understanding the mechanism of lithium-ion storage\nin α-Fe₂O₃-based materials. The as-prepared\nfree-standing TFN with excellent stability and high capacity can be\nan appropriate candidate for carbon-free anode material in LIBs.