Molten Salt Synthesis of Different Ionic Radii Metallic Compounds Doped Lithium Titanate Used in Li-Ion Battery Anodes

In order to systematically characterize the effects of ion doping on Li4Ti5O12 (LTO) through the molten salt method, different metallic compounds with varying ionic radii doped into LTO were investigated. The results show that doped ions (Al3+, Ni2+, Fe2+, Fe3+ and F-) with similar ionic radius as Li+, Ti4+ or O2- ions can enter into LTO, which leads to smaller particle size than pure LTO, therefore, increasing the specific surface area and shortening Li+ transfer path of LTO. However, La3+ with a much larger ionic radius cannot enter into LTO. Ion doping can enhance the intrinsic conductivity of LTO, thus improving the electrochemical performance of LTO. As the ionic radii of Fe2+ and Fe3+ are the closest to those of Li+ and Ti4+, Fe3O4 doped LTO exhibits the best electrochemical performance, an excellent first discharge capacity of 269.3 mAh.g(-1) at the 0.15 degrees C, good high-rate capability (123.4 mAh.g(-1) at 10 degrees C); even after 300 discharge/charge cycles, the discharge capacity is 141.1 mAh.g(-1), gives an excellent cycle performance with 12.4% loss of capacity at 1 degrees C rate. Due to these factors, Fe3O4 is the most suitable metallic compound doped in LTO via molten salt method.