Long-cycle performance of the hollow and sandwich structured of H-TiO2/Fe3O4/C anode material for lithium-ion batteries

First, a spherical Fe 3 O 4 was synthesized using the hydrothermal method, and subsequently coated with carbon to form a core–shell C/Fe 3 O 4 composite. The Fe 3 O 4 core was then dissolved in an etching solution to create a hollow carbon (H-C) structure. This H-C served as a substrate onto which a Fe 3 O 4 layer was deposited via the hydrothermal method, resulting in a hollow core–shell Fe 3 O 4 /C composite. Finally, the solvothermal method was employed to coat the Fe 3 O 4 /C composite with a layer of hydrogenated titanium dioxide (H-TiO 2 ), resulting in a hollow-structured H-TiO 2 /Fe 3 O 4 /C material. This structure not only ensures the formation of a dual-core shell structure, but also reduces the proportion of carbon material in the composite electrode, thereby enhancing the theoretical specific capacity of the composite electrode. The presence of H-TiO 2 and carbon improved the cyclic stability of Fe 3 O 4 within the composite. This hollow sandwich–structured composite demonstrated excellent electrochemical performance, delivering a discharge specific capacity of 629.5 mAh g −1 after 500 cycles at 0.2 A g −1 , along with a high initial coulombic efficiency of 80.6%.