Sub-micrometric Li4−xNaxTi5O12 (0 ≤ x ≤ 0.2) spinel as anode material exhibiting high rate capability

Abstract

The spinel Li4Ti5O12 has been doped by Na for the purpose of improving its cycle performance as an anode. The lattice parameter of Li4Ti5O12 increases due to the Na doping. SEM shows that all materials are well crystallized with a particle size in the range of 400–600 nm. The pristine Li4Ti5O12 sample has a bigger particle size than that of Na-doped samples. Although the doping does not change the crystallographic structure of Li4Ti5O12, they exhibit better cyclability at high charge–discharge rate compared with pristine Li4Ti5O12. Li3.85Na0.15Ti5O12 gives the best cycling performance, only 11.1% loss of capacity after 80 cycles at 2 C charge–discharge rate. Na-doped Li4Ti5O12 exhibits lower potential separation, indicating faster electron transfer kinetics and cycling reversibility. Electrochemical impedance spectroscopy demonstrates that the improved performance of the Na-doped Li4Ti5O12 is due to a small decrease in the charge transfer resistance, indicating high electrochemical activity during cycling. The excellent cycling and safety performance of the Na-doped Li4Ti5O12 electrodes are found to be due to the significantly increased ionic and electronic conductivity. Since fast charge–discharge performance is an important factor that needs to be considered in fabricating power batteries in industry, the Na-doped Li4Ti5O12 materials moves closer to real and large scale applications.