Single-step solid-state synthesis and characterization of Li4Ti5-xFexO12-y (0 <= x <= 0.1) as an anode for lithium-ion batteries

摘要

We carried out a single-step doping reduction, Li4Ti5-xFexO12-y (0 <= x <= 0.1) with Fe, by a facile solid-phase method with the objective of improving the electrochemical performance of Li4Ti5O12 (LTO). Unlike the conventional method of using an Fe salt as a dopant, elemental Fe is used here as both a reducing agent and a dopant. The Fe first reacts with TiO2 to form Ti3+ and Fe3+ ions; the Fe3+ ions then incorporate into the TiO2 crystal lattice through substitution of Ti by Fe; the amount of Ti3+/Ti4+ is increased as a result of charge compensation, which further improves the conductivity of the LTO, resulting in high electrochemical performance. The investigation of the electrochemical performance of lithium-ion batteries under low-voltage conditions is important for assessing their safety. Because LTO can provide a higher battery voltage and a discharge capacity at a lower voltage, the electrochemical behavior of LTO in the voltage range 0-3 V was also investigated. The modified Li4Ti5-xFexO12-y exhibits a capacity of 228.7 mA h g(-1) after 200 cycles, which is substantially higher than that of pure LTO (176.3 mA h g(-1)). In addition, the band structure and density of states (DOS) of the original and Fe-doped Li4Ti5O12 were calculated by first-principles calculations. The Li4Ti5-xFexO12-y (0 <= x <= 0.1) can provide a higher voltage, enabling its broad application in lithium-ion batteries because of its large discharge range, good electrochemical performance, and simple synthesis process.