context: Even though the SEI film is supposed to act as an insulator being a barrier for electron transfer, at the initial nucleation stages its structure may favor electron transport. This may occur because of the differences between the amorphous character of nucleating crystals and their bulk theoretical structures, as has been found in some bulk insulator materials where changes in the electronic conductivity were observed in ultra-thin films showing a semiconductor behavior. This capability of conducting electrons of imperfectly formed SEI nuclei and phases could contribute to the growth mechanism that keeps the SEI forming until it reaches hundreds of nanometers. Another important reason for the continuous SEI growth is the presence of radical charged species that result from the SEI reactions and are able to diffuse toward the vicinity of the electrolyte inducing further reactions. Several experimental and theoretical works have studied the various stages of the SEI formation and growth process while other authors have proposed the formation of artificial SEI layers by pretreating the anode before the battery is assembled. For the early stages of the SEI formation it is crucial to improve the understanding of electrolyte decomposition by characterizing the reaction mechanisms of electrolytes typically used in battery systems. It is known that carbonate solvents have low stability when implemented with Li-metal anodes, while ether-based solvents like dimethoxyethane (DME) and dioxalane (DOL) have shown better stability with respect to the Li-metal anode and are frequently used for these battery systems. However, solvent and salt molecules decomposition are still observed and in spite of the advances reached both from experimental and theoretical studies, the mechanisms of these processes are not yet well understood.
answer:  Li-metal