Electrochemical behaviors of a Li3N modified Li metal electrode in secondary lithium batteries

Abstract A lithium conductive Li 3 N film is successfully prepared on Li metal surface by the direct reaction between Li and N 2 gas at room temperature. X-ray diffraction (XRD), Auger electron spectroscopy (AES), cyclic voltammetry (CV), scanning electron microscopy (SEM), AC impedance, cathodic polarization and galvanostatic charge/discharge cycling tests are applied to characterize the film. The experimental results show that the Li 3 N protective film is tight and dense with high stability in the electrolyte. Its thickness is more than 159.4 nm and much bigger than that of a native SEI film formed on the lithium surface as received. An exchange current as low as 3.244 × 10 −7 A demonstrates the formation of a complete SEI film at the electrode|electrolyte interface with Li 3 N modification. The SEI film is very effective in preventing the corrosion of the Li electrode in liquid electrolyte, leading to a decreased Li | electrolyte interface resistance and an average short distance of 3.16 × 10 −3 cm for Li ion diffusion from electrolyte to Li surface. The Li cycling efficiency depends on N 2 exposing time and is obviously enhanced by the Li 3 N (1 h) modification. After cycling, a dense and homogeneous Li layer deposits on the Li 3 N (1 h) modified Li surface, instead of a loose and inhomogeneous layer on the Li surface as received.