Tin–Carbon Dual Buffer Layer to Suppress Lithium Dendrite Growth in All-Solid-State Batteries

All-solid-state lithium–metal batteries hold great promise because of their high energy density stemming from using an energy-dense lithium–metal anode. However, mitigating the dendritic lithium–metal growth, originating from heterogeneous lithium–metal deposition, is a priority to suppress short-circuit and extend cycle life. This study employs direct current (DC) magnetron sputter coating to deposit tin (Sn) and carbon (C) on a stainless steel (SUS) current collector to achieve uniform lithium–metal plating and improve cycling performance. In particular, we evaluated and compared two dual buffer layer designs, consisting of Sn and C: (1) a thin C layer is deposited on the Sn metal layer (SUS/Sn/C), and (2) the Sn metal layer is deposited on the thin C layer (SUS/C/Sn). This study demonstrated that the SUS/Sn/C buffer layer is more effective in suppressing lithium dendrite growth and improving cycling stability than the SUS/C/Sn buffer layer. The SUS/Sn/C buffer layer shows stable Li-plating/stripping cycling over 450 cycles without noticeable short-circuit. Ex situ and in situ characterization confirm the role of the SUS/Sn/C dual buffer layer: (i) the Sn metals result in a uniform lithium–metal deposition on the current collector and (ii) the carbon layer acts as a physical barrier to suppress the lithium dendrite growth toward the solid electrolyte because of its lithiophobic nature.