The Role of Interlayer Chemistry in Li-Metal Growth through a Garnet-Type Solid Electrolyte

Securing the chemical and physical stabilities of electrode/solid-electrolyte interfaces is crucial for the use of solid electrolytes in all-solid-state batteries. Directly probing these interfaces during electrochemical reactions would significantly enrich the mechanistic understanding and inspire potential solutions for their regulation. Herein, the electrochemistry of the lithium/Li7La3Zr2O12-electrolyte interface is elucidated by probing lithium deposition through the electrolyte in an anode-free solid-state battery in real time. Lithium plating is strongly affected by the geometry of the garnet-type Li7La3Zr2O12 (LLZO) surface, where nonuniform/filamentary growth is triggered particularly at morphological defects. More importantly, lithium-growth behavior significantly changes when the LLZO surface is modified with an artificial interlayer to produce regulated lithium depositions. It is shown that lithium-growth kinetics critically depend on the nature of the interlayer species, leading to distinct lithium-deposition morphologies. Subsequently, the dynamic role of the interlayer in battery operation is discussed as a buffer and seed layer for lithium redistribution and precipitation, respectively, in tailoring lithium deposition. These findings broaden the understanding of the electrochemical lithium-plating process at the solid-electrolyte/lithium interface, highlight the importance of exploring various interlayers as a new avenue for regulating the lithium-metal anode, and also offer insight into the nature of lithium growth in anode-free solid-state batteries.