摘要：Samples of Li 4 Ti 5 O 12-y solid solutions are synthesized by one-step solid-state carbothermal reduction reaction using Li 2 CO 3 , anatase, and carbon black under a nitrogen atmosphere. The underlying formation mechanism that leads to Li 4 Ti 5 O 12-y solid solutions is proposed. The formation mechanism of the Li 4 Ti 5 O 12-y solid solution is investigated by in situ variable temperature X-Ray diffraction (VT-XRD) and thermogravimetric analysis/differential scanning calorimetry (TGA-DSC). First, some Ti 4+ centers are converted to Ti 3+ (TiO 2 -TiO 2-x ) because of the presence of carbon black. Secondly, Li 2 CO 3 reacts with TiO 2-x (anatase) to form Li 2 TiO 3 . Thirdly, Li 2 TiO 3 reacts with TiO 2-x to form the Li 4 Ti 5 O 12-y solid solution, while anatase starts to transform into rutile at the same time. Rutile reacts with Li 2 TiO 3 to form Li 4 Ti 5 O 12-y at higher temperatures. The presence of Ti 3+ not only improves the electrical conductivity but also improves the ionic conductivity. As a result, the as-prepared material exhibits good rate capability and cycling stability with 99.3% capacity retention after 200 cycles.
