Structure and electrochemical performance of BaLi2-xNaxTi6O14 (0≤x≤2) as anode materials for lithium-ion battery

A series of BaLi2-xNaxTi6O14(0 <= x <= 2) compounds as lithium storage materials were synthesized by a facile solidstate method. X-ray diffraction Rietveld refinement shows that the Bragg positions correspond to the BaLi2Ti6O14, indicating a successful preparation. The Na+ ions doped BaLi2Ti6O14 compounds have larger unit-cell volume than the pristine one because ionic radius of Na+ ion is 55% larger than that of Li+ ion. SEM shows that the BaLi2-xNaxTi6O14 (x=0, 0.5 and 1) powders show similar irregular shaped particles between 500 and 1000 nm. However, BaLi2-xNaxTi6O14 (x=1.5 and 2) powders show similar rod-like shape. CV reveals that the passivating film is mainly formed during the first insertion process, and the solid electrolyte interface film on the surface of BaLi2-xNaxTi6O14 (0 <= x <= 2) is formed below 0.7 V in the first cycle. Compared with other samples, BaLi0.5Na1.5Ti6O14 exhibits higher reversible capacity, better rate capability and superior cyclability. BaLi0.5Na1.5Ti6O14 delivers the delithiation capacities of 162.1 mA h g(-1) at 50 mA g(-1), 158.1 mA h g-(1) at 100 mA g(-1), 156.7 mA h g(-1) at 150 mA g(-1), 152.2 mA h g(-1) at 200 mA g(-1), 147.3 mA h g(-1) at 250 mA g(-1) and 142 mA h g(-1) at 300 mA g(-1), respectively. An interesting thing is that BaNa2Ti6O14 as anode also shows an acceptable electrochemical performance. All these improved electrochemical performances of BaLi0.5Na1.5Ti6O14 are attributed to the lowest polarization and the highest lithium ion diffusion coefficient among all samples. Hence, BaLi0.5Na1.5Ti6O14 with excellent cycling performance, simple synthesis route and wide discharge voltage range can be a possible anode candidate for lithium-ion batteries.