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. <i>Ex situ</i> and <i>in situ</i> 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.