Preparation and electrochemical characterization of Li2+xNa2−xTi6O14 (0≤x≤0.2) as anode materials for lithium-ion batteries

In this work, a series of Li2+xNa2−xTi6O14 (0≤x≤0.20) are synthesized by a simple solid-state reaction method. All the as-prepared samples are high purity titanates and well crystallized with a particle size distribution in the range of 0.3–0.5 μm. Electrochemical analysis shows that Li2.05Na1.95Ti6O14 displays a higher working potential platform at 1.33 V than that about 1.28 V of other Li2+xNa2−xTi6O14 (x=0.00, 0.10, 0.15 and 0.20) samples. Charge/discharge results show that Li2.05Na1.95Ti6O14 presents higher charge capacities of 302.9 mA h g−1 for the first cycle than other four samples. After 50 cycles, Li2.05Na1.95Ti6O14 still delivers a reversible charge capacity of 277.6 mA h g−1, but Li2+xNa2−xTi6O14 (x=0.00, 0.10, 0.15 and 0.20) samples only present the charge capacities of 211.8, 232.1, 183.9 and 231.9 mA h g−1, respectively. Furthermore, Li2.05Na1.95Ti6O14 also provides a remarkable rate performance with the charge capacities of 241.2 mA h g−1 at 200 mA g−1, 228.2 mA h g−1 at 300 mA g−1 and 217.4 mA h g−1 at 400 mA g−1. In contrast, pristine Li2Na2Ti6O14 only delivers the lithium storage capacities of 207.0 mA h g−1 at 200 mA g−1, 194.5 mA h g−1 at 300 mA g−1 and 187.7 mA h g−1 at 400 mA g−1. All these improved electrochemical properties of Li2.05Na1.95Ti6O14 are attributed to the lowest polarization and the highest lithium ion diffusion coefficient among all the five samples.