Investigation of Graphite-based Interfacial Engineering in the Solid-State Lithium Metal Batteries with a Garnet-Structured Solid Electrolyte

Garnet-structured fast lithium-ion conductors are considered one of the most favorable options for developing high-energy-density lithium metal-based batteries. However, the high interface resistance between the electrode and electrolyte remains a primary challenge for its real-time application. In this study, we propose a productive method to enhance the lithium metal wettability of gallium-doped garnet (Li6.28Ga0.24La3Zr2O12) with a graphite interlayer. After lithiation, this functional layer considerably enhances the interface connection between gallium-doped garnet solid electrolyte and lithium metal; as such, the interface resistance was reduced from 970 to 37 Ω cm2. The improved interface resulted in a low and stable overpotential during galvanostatic charge and discharge cycling in lithium symmetric cells at 0.4 mA cm–2. Furthermore, a full Li|LiFePO4 battery with the surface-modified garnet electrolyte exhibits significantly enhanced charge and discharge capacity, Coulombic efficiency, and cycling stability.