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

抄録

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 C, good high-rate capability (123.4 mAh·g⁻¹ at 10 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 C rate. Due to these factors, Fe₃O₄ is the most suitable metallic compound doped in LTO via molten salt method.