Deeper Insights into the Morphology Effect of Na 2 Ti 3 O 7 Nanoarrays on Sodium-Ion Storage.

Na 2 Ti 3 O 7 -based anodes show great promise for Na + storage in sodium-ion batteries (SIBs), though the effect of Na 2 Ti 3 O 7 morphology on battery performance remains poorly understood. Herein, hydrothermal syntheses is used to prepare free-standing Na 2 Ti 3 O 7 nanosheets or Na 2 Ti 3 O 7 nanotubes on Ti foil substrates, with the structural and electrochemical properties of the resulting electrodes explored in detail. Results show that the Na 2 Ti 3 O 7 nanosheet electrode (NTO NSs) delivered superior performance in terms of reversible capacity, rate capability, and especially long-term durability in SIBs compared to its nanotube counterpart (NTO NTs). Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) investigations, combined with density functional theory calculations, demonstrated that the flexible 2D Na 2 Ti 3 O 7 nanosheets are mechanically more robust than the rigid Na 2 Ti 3 O 7 nanotube arrays during prolonged battery cycling, explaining the superior durability of the NTO NSs electrode. This work prompts the use of anodes based on Na 2 Ti 3 O 7 nanosheets in the future development of high-performance SIBs.