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.