Carbon coated Li₄Ti₅O₁₂ fibers: Relying on the lithium diffusivity in TiO₂–B crystal structure for high rate lithium battery

TiO₂–B nanofibers were synthesized by hydrothermal and ion-exchange methods. Subsequently, carbon coated Li₄Ti₅O₁₂ (C/Li₄Ti₅O₁₂) fibers were successfully synthesized by solid state reaction of TiO₂–B nanofibers, Li₂CO₃ and furfuralcohol in inert environment. These fibers are well crystallized with average diameter of about 500 nm at low reaction temperature of 650 °C. The fibrous morphology was remained due to the open crystal structure of TiO₂–B that facilitates lithium diffusion into TiO₂–B crystal structure during calcination. Each C/Li₄Ti₅O₁₂ fiber was assembled by Li₄Ti₅O₁₂ nanoparticles of 20 nm in size and coated by a thin layer of carbon. Taking advantage of the fiber morphology and electron conductive carbon layer, the C/Li₄Ti₅O₁₂ fibers presented outstanding rate and cycling performance as anode of lithium-ion batteries. A high capacity of 174.6 mAh g⁻¹ was achieved at a rate of 1 C (1 C = 175 mAh g⁻¹), which slowly decreased to 109.1 mAh g⁻¹ at the rate of 20 C. Without carbon layer, the material experienced structural collapse during the hydrothermal reaction and presented a specific capacity of 144.5 mAh g⁻¹ at 1 C, which further decreased to 77.3 mAh g⁻¹ at 20 C. Excellent cycling stability was achieved in both Li₄Ti₅O₁₂ and C/Li₄Ti₅O₁₂ with up to 50 cycles.