Nickel Impurities in the Solid-Electrolyte Interphase of Lithium-Metal Anodes Revealed by Cryogenic Electron Microscopy

Dissolution of transition metals from high-voltage cathodes and their incorporation into the solid-electrolyte interphase (SEI) of carbonaceous anodes drastically reduces the lifetime of Li-ion batteries. The effects of dissolved transition metals on the performance of carbonaceous anodes are well characterized; however, the impact on Li-metal anode performance and the SEI is rarely considered. Here, we use cryogenic electron microscopy to reveal the impact of dissolved Ni on the SEI formation process on Li-metal. A link between Ni incorporation into the SEI and the failure of Li-metal batteries is established. We find that Ni is reduced into its metallic state and incorporates as small clusters into the SEI, locally changing the chemistry and nanostructure of the SEI. These chemical and nanostructure changes locally modify the Li-ion and electron transport properties of the SEI, accelerating electrolyte decomposition, increasing formation of dead Li, and ultimately causing failure.