Stable all-solid-state lithium metal batteries enabled by ex-situ stress buffer layer and in-situ ion flow regulator

All-solid-state lithium metal batteries (ASSLMBs) hold tremendous potential due to their high energy density and enhanced safety compared with liquid lithium batteries. However, their commercialization is largely hindered by the uncontrollable lithium dendrites, which induce short circuits and poor cycling stability. Lithium dendrite growth can be inhibited through two main approaches: controlling lithium deposition behavior and managing internal stress caused by volume changes. In this work, we designed an artificial interface layer composed of an Ag₂O upper layer and a Li-Ag alloy bottom layer through a solution-based displacement reaction. The Ag₂O layer serves to homogenize the distribution of lithium-ion concentration, thereby enabling uniform lithium deposition. Simultaneously, the Li-Ag alloy solid solution, structured as a porous microdomain formed by nanoparticles, helps buffer the plating-induced stress within bulk lithium. Thanks to the synergistic effect of the Ag₂O and Li-Ag alloy layer, Li symmetric cells achieved a high critical current density of over 1.2 mA cm⁻² at a capacity of 0.2 mA h cm⁻², along with ultra-stable cycling for over 4500 h at 0.2 mA cm⁻². Moreover, ASSLMBs paired with LiFePO₄ cathodes exhibited superior rate capabilities and stable cycling after 250 cycles at 0.5C. Even when paired with Li₂S cathodes, enhanced electrochemical performance was observed after 200 cycles at 0.2C. This study provides an effective strategy for the development of ASSLMBs through the synergistic regulation of lithium deposition and the mitigation of electroplating-induced stress, ultimately suppressing the formation of lithium dendrites.