Lamination Pressure Governs the Effectiveness of Sn Buffer Layers in Low-Pressure All-Solid-State Lithium Metal Batteries

Abstract All-solid-state lithium-metal batteries require stable Li plating/stripping under low stack pressures relevant to practical operation. Here, Sn was used as a model Li-alloying buffer layer to clarify how lamination pressure affects interfacial stability. By independently varying lamination pressure and operating stack pressure, this study decoupled the effects of initial interfacial contact formation from those of external pressure during Li plating/stripping. High-pressure lamination improved contact between the lithiated Sn layer and the solid electrolyte, enabling facile Li+ transport through the buffer layer and promoting Li deposition beneath the buffer layer rather than at the solid-electrolyte/buffer layer interface. Consequently, highly laminated Sn–Li electrodes exhibited improved Li utilization, lower nucleation overpotential, enhanced short-circuit resistance, and improved resistance for void-induced contact loss under low stack pressure. Symmetric- and full-cell tests confirmed that the Sn buffer layer mitigates void-induced contact loss, whereas pristine Li rapidly fails at a stack pressure of 1 MPa.