Monodispersed mesoporous Li4Ti5O12 submicrospheres as anode materials for lithium-ion batteries: morphology and electrochemical performances

Abstract

Although nanosizing Li₄Ti₅O₁₂ (LTO) materials is an effective way to improve their rate performances, their low tap density and first cycle coulombic efficiency limit their practical applications. To tackle these problems while preserving the advanced rate performances, monodispersed mesoporous LTO submicrospheres are developed here. These submicrospheres are synthesized via a solvothermal method using TiO₂ submicrospheres and LiOH as precursors followed by a mild calcinations. The roles of the solvent used in the solvothermal process and calcination temperature are systematically investigated and optimized. The LTO submicrospheres fabricated by the solvothermal process using a water–ethanol (60 vol%) solvent followed by a calcination process at 600 °C reveal a large sphere size of 660 ± 30 nm with a small primary particle size of 20–100 nm, a large specific surface area of 15.5 m² g⁻¹, an appropriate pore size of 4.5 nm and an ultra-high tap density of 1.62 g cm⁻³. Furthermore, they show high crystallinity and no blockage of Li⁺ ion transportation pathways. Due to the novel morphology and ideal crystal structure, these submicrospheres exhibit outstanding electrochemical performances. They display a high first cycle coulombic efficiency of 93.5% and a high charge capacity of 179 mA h g⁻¹ at 0.5 C between 1.0 and 2.5 V (vs. Li/Li⁺), surpassing the theoretical capacity of LTO. Their charge capacity at 10 C is as high as 109 mA h g⁻¹ with a capacity retention of 97.8% over 100 cycles. Therefore, this LTO material can be a superior and practical candidate for the anodes of high-power lithium-ion batteries.