Facile synthesis of hierarchically porous Li4Ti5O12 microspheres for high rate lithium ion batteries

Abstract

A novel approach has been developed to synthesize hierarchically porous Li₄Ti₅O₁₂ microspheres assembled by well-crystalline nanoparticles. The fabrication process is very simple, involving only hydrothermal treatment of commercial anatase TiO₂ powder in LiOH solution and a following calcination procedure without employing any surfactants or templates. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption/desorption analysis were used to characterize their morphologies and structures. Such Li₄Ti₅O₁₂ nano/microspherical superstructures, with sizes of ca. 4 μm in diameter, exhibits rich hierarchical pores and a specific surface area of 57.5 m² g⁻¹. A possible growth mechanism of the nano/microspherical superstructure is further discussed. The calcination temperature has a great effect on the crystal structure and electrochemical properties of the materials. The hierarchically porous Li₄Ti₅O₁₂ microspheres annealed at 700 °C have the perfect crystallization and optimal particle size, which can deliver good coulombic efficiency, ultrahigh rate capability at high rates, and excellent capacity retention over 200 cycles.