Owing to its high energy density and light weight, Li-ion batteries have taken away over half of the worldwide rechargeable battery market. However, the safety issues of Li-ion batteries that originate from the combustible organic electrolyte are of great concern recently. Solid-state batteries using powder compact solid electrolytes (PCSE) are promising options toward safer and higher energy density batteries due to the utilization of inorganic electrolyte and metal lithium as anode, however, the high solid-solid interfacial resistance between the lithium metal and the solid electrolyte is still a challenge.

In this work, we demonstrate reversible plating and stripping of dendrite-free metallic-lithium with a reduced anode/PCSE interfacial resistance by introducing a thin interfacial layer formed by heating. First, the PCSE which has an ionic conductivity of ~ 10^-4 S/cm at room temperature, was synthesized by mechanical milling, and characterized using NMR, DSC, IR spectroscopy, and Raman spectroscopy. Next, the PCSE was tested in symmetric cells for electrochemical impedance spectroscopy and cycling. To address the high solid-solid interfacial resistance and short-circuiting dendrite problems, we demonstrate a simple strategy to engineer the lithium-PCSE interface by forming an in-situ interlayer via a heat treatment. The area specific resistance of 573.6 Ω/cm² has been successfully achieved with a 0.9 mm thickness pellet under a current density of 0.1 mA/cm². These results provide a promising PCSE membrane that can be applied to lithium metal battery and other energy storage application, such as lithium sulfur batteries.