Preparation, electrochemical characterization and in-situ kinetic observation of Na2Li2Ti6O14 as anode material for lithium ion batteries

A novel lithium storage material Na2Li2Ti6O14 is synthesized and reported as anode material for lithium-ion batteries in this paper. The synthesis of Na2Li2Ti6O14 is performed by using a simple solid state reaction route. No impurity can be detected in the final product obtained at a temperature of 900 °C. As-formed Na2Li2Ti6O14 is composed of irregular solid particles with the size ranging from 200 to 400 nm. Using as anode material, Na2Li2Ti6O14 exhibits flat lithiation/delithiation plateaus with average working potential of 1.28 V. Electrochemical testing results show that Na2Li2Ti6O14 can deliver a reversible capacity of 74 mA h g−1 with capacity retention of 98.01% upon 50 cycles. Moreover, it also displays excellent rate performance with a charge capacity of 69.5 mA h g−1 at 200 mA g−1, 64.7 mA h g−1 at 300 mA g−1, 60.7 mA h g−1 at 400 mA g−1, and 57.9 mA h g−1 at 500 mA g−1. The outstanding kinetic behavior is attributed to the high lithium ion diffusion coefficient in Na2Li2Ti6O14, which shows the value ranging from 10−14 to 10−12 cm2 s−1. Owing to the rapid diffusion kinetics, symmetrical structural change at high rates can be observed by in-situ X-ray diffraction during charge-discharge process.