Mitigating Interfacial Mismatch between Lithium Metal and Garnet-Type Solid Electrolyte by Depositing Metal Nitride Lithiophilic Interlayer

Solid-state lithium batteries are generally considered as the next-generation battery technology that benefits from inherent nonflammable solid electrolytes and safe harnessing of high-capacity lithium metal. Among various solid-electrolyte candidates, cubic garnet-type Li₇La₃Zr₂O₁₂ ceramics hold superiority due to their high ionic conductivity (10^-3 to 10^-4 S cm^-1) and good chemical stability against lithium metal. However, practical deployment of solid-state batteries based on such garnet-type materials has been constrained by poor interfacing between lithium and garnet that displays high impedance and uneven current distribution. Herein, we propose a facile and effective strategy to significantly reduce this interfacial mismatch by modifying the surface of such garnet-type solid electrolyte with a thin layer of silicon nitride (Si₃N₄). This interfacial layer ensures an intimate contact with lithium due to its lithiophilic nature and formation of an intermediate lithium-metal alloy. The interfacial resistance experiences an exponential drop from 1197 to 84.5 Ω cm². Lithium symmetrical cells with Si₃N₄-modified garnet exhibited low overpotential and long-term stable plating/stripping cycles at room temperature compared to bare garnet. Furthermore, a hybrid solid-state battery with Si₃N₄-modified garnet sandwiched between lithium metal anode and LiFePO₄ cathode was demonstrated to operate with high cycling efficiency, excellent rate capability, and good electrochemical stability. This work represents a significant advancement toward use of garnet solid electrolytes in lithium metal batteries for the next-generation energy storage devices.