Li3N interlayer enables stable long-term cycling for sulfide-based all-solid-state Li metal batteries

All-solid-state lithium metal batteries have attracted much attention for their high energy density and safety. Lithium argyrodite is an attractive solid-state electrolyte (SSE) due to its high ionic conductivity and excellent processability at room temperature. However, the poor interfacial contact and side reactions between Li metal and lithium argyrodite seriously hinder its practical applications. In this work, we prepared the lithium argyrodite Li5.5PS4.5Cl1.5 (LPSCl) with room temperature lithium ion conductivity up to 11.2 mS/cm, and improved the interfacial stability between Li metal and LPSCl by introducing a Li3N interlayer with high ionic conductivity. As a result, the interfacial resistance can be reduced to as low as 1.4 Ω cm2 in symmetric cells. The symmetrical cells can be stably cycled for >650 h at a current density of 0.5 mA cm−2, with a critical current density as high as 1.9 mA cm−2. Moreover, a Li/Li3N-LPSCl/NCM811 all-solid-state lithium battery also displays high cycling efficiency and stability over 260 cycles at 50 °C. This work provides a new idea for further optimizing the interface of all-solid-state lithium metal batteries.