Low-temperature synthesis of lithium titanate nanoparticles assisted by ball milling and their structural and electrochemical performance as anode materials for Li-ion batteries

In this work, we refer on simple synthesis of spinel based Li₄Ti₅O₁₂ (LTO) by combination of mechanical pre-activation of precursors followed by low-temperature calcination at 600 grad C. The phase evaluation and its purity is examined by analyses of data provided X-ray powder diffraction and ⁶Li MAS NMR. The charge capacity of the LTO with average crystallite size 150 nm was found to be 142 mAh/g, i.e. ∼81 % of theoretical capacity. The capacity of our optimised material is superior to that of commercially available spinel, although the as-synthesized LTO is characterized by small BET-specific surface area. The superior properties of our material were also demonstrated by galvanostatic charging/discharging. In order to modify crystallite size and BET-specific surface area, as-prepared samples were further treated by ball milling. X-ray diffraction analysis proves the presence of majority of Li₄Ti₅O₁₂ phase with small amount of rutile and WC impurities with negligible effect on electrochemical properties. Transmission electron microscopy analysis revealed presence of Li₄Ti₅O₁₂ in different morphologies. Cyclic voltammetry of Li insertion and galvanostatic chronopotentiometry at 1C rate confirm the highest charge capacity for Li₄Ti₅O₁₂ spinel with surface area of 21 m² g^-1. Due to optimized ratio of two particular morphologies this material possesses excellent long time cycling stability during galvanostatic chronopotentiometry at 1, 2 and 5C. Its discharge capacities reach 170 mAh g-1 at 1C (∼97% of theoretical value), 167 mAh g^-1 at 2C and 160 mAh g^-1 at 5C rates with 100% coulombic efficiency. The capacity drop was less than 1 % for charging rates of 1 and 2C and about 5 % at 5C. Accordingly, the effect of crystallite size and BET-surface area on the electrochemical properties of synthesized LTO are discussed within this work (authors)