Introducing Hybrid Defects of Silicon Doping and Oxygen Vacancies into MOF‐Derived TiO2–X@Carbon Nanotablets Toward High‐Performance Sodium‐Ion Storage

Titanium dioxide (TiO2) is a promising anode material for sodium–ion batteries (SIBs), which suffer from the intrinsic sluggish ion transferability and poor conductivity. To overcome these drawbacks, a facile strategy is developed to synergistically engineer the lattice defects (i.e., heteroatom doping and oxygen vacancy generation) and the fine microstructure (i.e., carbon hybridization and porous structure) of TiO2‐based anode, which efficiently enhances the sodium storage performance. Herein, it is successfully realized that the Si‐doping into the MIL‐125 metal‐organic framework structure, which can be easily converted to SiO2/TiO2–x@C nanotablets by annealing under inert atmosphere. After NaOH etching SiO2/TiO2–x@C which contains unbonded SiO2 and chemically bonded SiOTi, thus the lattice Si‐doped TiO2–x@C (Si‐TiO2–x@C) nanotablets with rich Ti3+/oxygen vacancies and abundant inner pores are developed. When examined as an anode for SIB, the Si‐TiO2–x@C exhibits a high sodium storage capacity (285 mAh g−1 at 0.2 A g−1), excellent long‐term cycling, and high‐rate performances (190 mAh g−1 at 2 A g−1 after 2500 cycles with 95.1% capacity retention). Theoretical calculations indicate that the rich Ti3+/oxygen vacancies and Si‐doping synergistically contribute to a narrowed bandgap and lower sodiation barrier, which thus lead to fast electron/ion transfer coefficients and the predominant pseudocapacitive sodium storage behavior.