Synthesis and electrochemical performance of F-doped Li4Ti5O12 for lithium-ion batteries

F-doped Li 4 Ti 5 O 12 anode materials in the form of Li 4 Ti 5 O 12− x F x (0   ≤   x   ≤   0.5) are synthesized successfully via a solid-state reaction. The structure and electrochemical properties of the as-prepared powders are investigated. The Li 4 Ti 5 O 12− x F x ( x   =   0.3) sample exhibits an outstanding electrochemical performance among all the samples in a potential range from 0.01 to 2.5   V, and delivers higher discharge capacity and better long-term cycling stability compared with the pristine Li 4 Ti 5 O 12 . The initial specific discharge capacity is 234.5   mAh   g −1 at a density of 85   mA   g −1 , and remains about 138   mAh   g −1 over 500 cycles when the current density increases to 340   mA   g −1 . The excellent electrochemical performance could be attributed to the substitution of F − into O 2− site, which can increase the amount of Ti 3+ /Ti 4+ mixing as charge compensation, leading to the decrease of the charge transfer resistance and improvement of the lithium ion diffusion in Li 4 Ti 5 O 12− x F x .