Experimental visualization of the diffusion pathway of sodium ions in the Na3[Ti2P2O10F] anode for sodium-ion battery

Sodium-ion batteries have attracted considerable interest as an alternative to lithium-ion batteries for electric storage applications because of the low cost and natural abundance of sodium resources. The materials with an open framework are highly desired for Na-ion insertion/extraction. Here we report on the first visualization of the sodium-ion diffusion path in Na[TiPOF] through high-temperature neutron powder diffraction experiments. The evolution of the Na-ion displacements of Na[TiPOF] was investigated with high-temperature neutron diffraction (HTND) from room temperature to 600°C; difference Fourier maps were utilized to estimate the Na nuclear-density distribution. Temperature-driven Na displacements indicates that sodium-ion diffusion paths are established within the ab plane. As an anode for sodium-ion batteries, Na[TiPOF] exhibits a reversible capacity of ∼100 mAh g with lower intercalation voltage. It also shows good cycling stability and rate capability, making it promising applications in sodium-ion batteries.This work is financially supported by the National Science Foundation of China (NSFC) (Grant Nos. 51372271, 51172275) and the start up grant from Institute of Physics (IOP). J. Alonso is grateful to the Spanish Ministry of Economy and Competitiveness for granting the project MAT2013-41099-R, and ILL for making all facilities available for the neutron diffraction experiments