Enhancing the electrochemical performance of Li4Ti5O12 anode materials by codoping with Na and Br

Abstract

Li4Ti5O12 (LTO) anode materials have become a research hotspot due to their "zero strain" characteristics. However, LTO has shortcomings such as a low capacity and rate performance, which severely restrict its development. In this work, Na+- and Br-- codoped LTO was successfully prepared by the sol-gel method, which effectively improved the capacity and high-rate performance. According to morphology and structure characterization, codoping retains the spinel crystal lattice and results in a more uniform phase and smaller particle size. Na+ doped at Li sites expands the lithium layer spacing, promoting the migration of Li+. Br- doped at O positions forms stronger covalent bonds with Ti, improving structural stability. Long-cycle and rate performance tests show that NB3-LTO exhibits the best electrochemical performance. The discharge capacity of NB3-LTO is 490.2 mAh g−1 at 0.2 C and 243.0 mAh g−1 at 10 C, while the corresponding values for pure LTO are only 158.5 and 66.4 mAh g−1. Codoping increased the discharge capacity 3.1- and 3.7- times respect to pure LTO at 0.2 and 10 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests show that the Li+ diffusion coefficient increases and the electrochemical impedance decreases. All test results show that codoping with Na+ and Br- is a feasible method to produce LTO anode materials with outstanding comprehensive performance.