Improving the structural stability and electrochemical performance of Na 2 Li 2 Ti 6 O 14 nanoparticles via MgF 2 coating.

To improve their electrochemical performance and structural stability, Na 2 Li 2 Ti 6 O 14 (NLTO) nanoparticles were synthesized and then coated with a very thin MgF 2 layer. Microscopy confirmed that the MgF 2 -NLTO particles are about 150-250 nm in size, and that the thickness of the MgF 2 layer for the MgF 2 -NLTO-5 sample is ∼5 nm. Electrochemical measurements showed that the charge-discharge specific capacities of the five samples under a current density of 50 mA g -1 after 100 cycles are 110.4/110.7, 150.7/151.3, 181.1/182.1, 205.7/206.9 and 238.9/239.2 mA h g -1 , showing that the performance of MgF 2 -NLTO-5 is the best among all the samples. Thanks to the thin coating layer, the polarization of the anode was reduced significantly, and its reversibility and lithium diffusion dynamics were also improved obviously. The performance improvement can be attributed to the suppression of surface corrosion and the enhancement of structural stability.