Facile synthesis of surface fluorinated-Li₄Ti₅O₁₂/carbon nanotube nanocomposites for a high-rate capability anode of lithium-ion batteries

Lithium titanate (Li₄Ti₅O₁₂, LTO) with a spinel structure has attracted considerable attention as a promising anode material for application in lithium-ion batteries (LIBs) with high stability and long cycle life. However, the rate characteristics of the battery deteriorate due to its low electronic conductivity. In this study, a uniform nanocomposite was easily obtained by complexing bulk LTO particles and carbon nanotubes (CNTs) via mechanofusion. Additionally, without using hazardous reagents, the surface of the LTO/CNT nanocomposites could be easily fluorinated via a simple post-treatment using ammonium fluoride (NH₄F). It was demonstrated that the degree of fluorination of the LTO/CNT nanocomposites could be easily controlled by adjusting the amount of NH₄F. The surface fluorinated-LTO/CNT nanocomposites, in which the main strategies for improving electrical conductivity were introduced simultaneously, showed excellent electrochemical performance as anodes for LIBs. In particular, the optimized surface fluorinated-LTO/CNT nanocomposites not only exhibited a high specific capacity of 170.2 mAh g⁻¹ at 0.2 C, but also maintained a capacity of ∼140 mAh g⁻¹ at a high rate of 20 C, which was almost 2.3 times higher than that of bulk LTO particles.