Elucidating the Mechanism of Solid-Electrolyte Interphase Formation in Hybrid Aqueous Zn-Ion Batteries

The formation of a favorable solid-electrolyte interphase (SEI) is essential to the reversible performance of zinc metal anodes in aqueous solutions. Thus far, it has been well agreed that the interphase layer should be passivating, ionically conductive, electronically insulating, and ideally self-repairable. When comprised of both organic and inorganic components, an SEI can effectively prevent hydrogen evolution reaction (HER) and corrosion on the metal surface, resulting in increased Coulombic efficiency and overall longevity. Here, we report the use of in-depth spectroscopic and electrochemical techniques to understand the unique solvation and decomposition of dimethyl carbonate (DMC) in high concentrated zinc water-in-salt electrolyte. Nuclear Magnetic Resonance (NMR) of both the liquid and solid states reveal an unusual dual reaction pathway that allows for the formation of a hybrid organic/inorganic SEI capable of achieving unprecedented capacity retention for zinc metal batteries.