Synthesis and characterization of F-doped nanocrystalline Li4Ti5O12/C compounds for lithium-ion batteries

Abstract

The F-doped and carbon coated Li₄Ti₅O_12−xF_x/C (LTOF/C) composite anode materials are synthesized via a conventional solid-state reaction with lithium citric acid as the conductive carbon source, and LiF as the fluorine source. The structure and electrochemical properties of the LTOF/C materials are investigated and the effects of carbon coating and F ion doping on the performance of as-prepared materials are discussed. Under a potential range from 0.01 to 2.5 V, LTOF/C exhibits better reversibility and higher cyclic stability compared with LTO and LTO/C, especially at high current rates. The initial specific discharge capacity is 325.6 mA h g⁻¹ at a current density of 170 mA g⁻¹, and remains about 165 mA h g⁻¹ over 1000 cycles when the current density increases to 850 mA g⁻¹. The main factors influencing the excellent performances should be attributed to the cooperation of the F-doping and carbon-coating, which can increase the amount of mixed Ti³⁺/Ti⁴⁺, leading to improved ionic conductivity and electron conductivity in LTO at the same time.