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

F-doped Li4Ti5O12 anode materials in the form of Li4Ti5O12−xFx (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 Li4Ti5O12−xFx (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 Li4Ti5O12. 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 O2− site, which can increase the amount of Ti3+/Ti4+ mixing as charge compensation, leading to the decrease of the charge transfer resistance and improvement of the lithium ion diffusion in Li4Ti5O12−xFx.