Facile synthesis of nanorods Na2Ti6O13 as anode materials for high-performance sodium ion batteries

In this study, Na2Ti6O13 nanorods with large interlayer spacing (about 0.798 nm) were synthesized by the hydrothermal and solid-phase sintering methods, and applied to the anode of sodium ion batteries (SIBs). The influence of different calcination temperatures on the electrochemical properties of Na2Ti6O13 nanorods were all studied. Benefitting from the nanorods structure and the large interlayer spacing, the Na2Ti6O13 prepared at 800 °C possessed fast Na+ diffusion and achieved high discharge capacities of 168.2 and 115.2 mA h g−1 at different current densities of 20 and 500 mA g−1, respectively, and remained at 131.1 and 96.7 mA h g−1 after 100 cycles, which exhibited the best cycling stability, fast Na+ diffusion characteristics, and excellent rate performance. Supported by electrochemical impedance spectroscopy, we found that the value of Rct became larger and the DNa+ became smaller with the progress of charge and discharge, which might be the cause of the decrease in the specific discharge capacity. The detailed analysis of cyclic voltammetry test confirmed that the proportion of pseudo-capacitance gradually decreased with the electrochemical reaction process keeping, from 83.8% at the beginning to 60.9% at the 100th cycle. This work establishes a valuable basis for the future study of Na2Ti6O13 as outstanding anode material for SIBs.