Fig. 4
Cryo-EM study on the SEI structure in the presence of nitrate. a Low-magnification and b high-resolution TEM images of Li deposits in 0.5 M LiPF6 EC/DEC electrolyte saturated with NO3– at a current density of 0.5 mA cm–2 for 150 s. The white line in b delineates the boundary between metallic Li and SEI. Scale bars, 200 nm in a and 10 nm in b. c Magnified TEM image and d the corresponding schematic of the orange region outlined in b showing the bilayered structure of SEI. The outside is a dense layer of Li2O displaying clear lattice fringes, and the inside is an amorphous matrix with crystalline domains (Li2O and Li2CO3) dispersed randomly throughout. Scale bar, 2 nm in c. e Energy-filtered TEM mapping of elemental distributions of Li, C, and O across the Li deposits and the corresponding unfiltered TEM image of the region. Scale bar, 100 nm. f Low-magnification and g high-resolution TEM images of Li deposits in 0.5 M LiPF6 EC/DEC electrolyte without NO3–. The SEI showed a mosaic model with crystalline domains dispersed in an amorphous matrix. Scale bars, 100 nm in f and 2 nm in g
