Experimental visualization of the diffusion pathway of sodium ions in the Na(3)[Ti(2)P(2)O(10)F] 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(3)[Ti(2)P(2)O(10)F] through high-temperature neutron powder diffraction experiments. The evolution of the Na-ion displacements of Na(3)[Ti(2)P(2)O(10)F] 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(3)[Ti(2)P(2)O(10)F] exhibits a reversible capacity of ~100 mAh g(−1) with lower intercalation voltage. It also shows good cycling stability and rate capability, making it promising applications in sodium-ion batteries.