Novel Construction of Heterostructured FeTiO₃/Fe_2.75Ti_0.25O₄ Mesoporous Nanodisks with Both High Capacity and Stable Cycling Life for Lithium-Ion Storage

Iron titanium oxides with the advantages of intercalation and conversion mechanisms are the promising anodes for high-energy-density and high-power-density lithium-ion batteries (LIBs). Herein, high-capacity Fe2.75Ti0.25O4 is first utilized for LIBs and combined with stable FeTiO3 to construct mesoporous heterostructures via introducing a ferrous precursor on Ti-based metal–organic frameworks and subsequent annealing treatment to solve the problem of low electronic conductivity and agglomeration during cycling for iron titanium oxides. Positive advantages including the large specific surface area provided by numerous nanoparticles, moderate volume expansion resulting from the porous structure and TiO2 matrix, rich lattice defects, and distinguished electronic structures introduced by abundant phase boundaries are obtained to boost the kinetic properties in the FeTiO3/Fe2.75Ti0.25O4 composite. The Fe–Ti–O electrode displays a high capacity of 735 mA h g–1 at 0.1 A g–1 and long cycle life with a capacity retention of 94.3% after 600 cycles at 1 A g–1. Moreover, good electrochemical properties can also be verified in solid-sate batteries and Fe–Ti–O//LiFePO4 full batteries. Furthermore, ex situ X-ray diffraction combined with X-ray photoelectron spectroscopy is used to investigate the reaction mechanism of Fe–Ti–O during the charge/discharge processes.