Effect of current density on the solid electrolyte interphase formation at the lithium divide Li6PS5Cl interface

The interface between the Li metal electrode and inorganic solid electrolyte is crucial for developing reliable all-solid-state Li batteries. Here, the authors show that the Li plating current density distinctly affects the chemistry and morphology of interphase components formed at the interface. Understanding the chemical composition and morphological evolution of the solid electrolyte interphase (SEI) formed at the interface between the lithium metal electrode and an inorganic solid-state electrolyte is crucial for developing reliable all-solid-state lithium batteries. To better understand the interaction between these cell components, we carry out X-ray photoemission spectroscopy (XPS) measurements during lithium plating on the surface of a Li6PS5Cl solid-state electrolyte pellet using an electron beam. The analyses of the XPS data highlight the role of Li plating current density on the evolution of a uniform and ionically conductive (i.e., Li3P-rich) SEI capable of decreasing the electrode divide solid electrolyte interfacial resistance. The XPS findings are validated via electrochemical impedance spectrsocopy measurements of all-solid-state lithium-based cells.