Interfacial Engineering for Lithium Metal Batteries Employing Garnet-Type Electrolyte

Garnet-type solid electrolytes, represented by the composition Li₇La₃Zr₂O₁₂ and its derivatives, have recently garnered significant attention due to their good compatibility with lithium metal anode. However, several issues remain unsolved, hindering the commercialization of lithium metal batteries employing garnet-type electrolytes: (1) Carbonates and hydroxides easily form on the surface of garnet electrolytes, leading to high interfacial resistance when incorporated into batteries. (2) While the chemical stability of garnet-type electrolytes against lithium metal is reasonably good, it is frequently observed that lithium dendrites penetrate through the electrolyte layer, causing short circuits between the cathode and anode. (3) During cell discharge or lithium metal stripping, voids often form at the interface. This results in fluctuations in local current density, accelerates short-circuiting, and worsens cycling stability. In this presentation, we will demonstrate that surface treatment of garnet with acid and the introduction of a carbon or carbon-metal composite interlayer are highly effective in addressing these issues. Stable cell cycling performance is achieved even at room temperature, with an areal capacity comparable to that of commercial lithium-ion batteries. We will also discuss the working mechanisms of these methods.