Porous cake-like TiO₂ derived from metal-organic frameworks as superior anode material for sodium ion batteries

Porous cake-like TiO₂ was prepared simply by annealing Ti-based metal-organic frameworks templates. The morphology, structure and electrochemical performance of porous TiO₂ were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption-desorption, galvanostatic charge/discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. When used as an anode for sodium ion batteries, porous TiO₂ exhibits a maximum charge capacity of 250 mAh g⁻¹ after 50 cycles at a current density of 50 mA g⁻¹ and delivers a remarkably stable reversible capacity of 173 mA g⁻¹ after 2500 cycles even at a high current density of 1 A g⁻¹. The excellent electrochemical performance is attributed to the unique porous structure and suitable pore size of porous TiO₂.