Mengmeng Lao

Enhanced lithium storage property of Na-doped Li2Na2Ti6O14 anode materials for secondary lithium-ion batteries

In this paper, a series of Na-doped Li2Na2Ti6O14 samples are synthesized by a simple solid-state reaction method through Li-site substitution with Na. Morphology observation shows that all five materials are well crystallized with a particle size in the range of 150–300 nm. Electrochemical analysis shows that Li1.95Na2.05Ti6O14 exhibits lower charge–discharge polarization (0.05 V) than that (0.11 V) of other Li2−xNa2+xTi6O14 samples (x = 0.00, 0.10, 0.15, 0.20). As a result, Li1.95Na2.05Ti6O14 has the highest initial charge capacity of 243.6 mA h g−1, and maintains a reversible capacity of 210.7 mA h g−1 after 79 cycles. For comparison, Li2−xNa2+xTi6O14 (x = 0.00, 0.10, 0.15 and 0.20) samples only hold a reversible capacity of 159.1, 203.5, 190.1 and 156.7 mA h g−1, respectively. Moreover, Li1.95Na2.05Ti6O14 also delivers the best rate performance compared with the other four samples, with a charge capacity of 221.1 mA h g−1 at 200 mA g−1, 211.9 mA h g−1 at 300 mA g−1, and 198.7 mA h g−1 at 400 mA g−1. Besides, the reversible in situ structural evolution proves that Li1.95Na2.05Ti6O14 is a stable host for lithium storage. All the improved electrochemical properties of Na-doped Li2Na2Ti6O14 should be attributed to the Na-doping with low content, which reduces the charge–discharge polarization and improves the ionic conductivity.