The solid electrolyte interphase (SEI) is regarded as the most complex but the least understood constituent in secondary batteries using liquid and solid electrolytes. The dearth of such knowledge in all-solid-state battery (ASSB) has hindered a complete understanding of how certain solid-state electrolytes, such as LiPON, manifest exemplary stability against lithium metal. By employing cryogenic electron microscopy (cryo-EM), the interphase between lithium metal and LiPON is successfully preserved and probed, revealing a multilayer-mosaic SEI structure with concentration gradients of nitrogen and phosphorus, materializing as crystallites within an amorphous matrix. This unique SEI nanostructure is less than 80 nm and is stable and free of any organic lithium-containing species or lithium fluoride components, in contrast to SEIs often found in state-of-the-art organic liquid electrolytes. Our findings reveal insights on the nanostructures and chemistry of such SEIs as a key component in lithium metal batteries to stabilize lithium metal anode.

在使用液体和固体电解质的二次电池中，固体电解质中间相（SEI）被认为是最复杂但了解最少的组分。全固态电池（ASSB）缺乏此类知识，妨碍了对某些固态电解质（如LiPON）如何表现出对锂金属的示例性稳定性的完整理解。通过使用低温电子显微镜（cryo-EM），成功地保护和探测了锂金属和LiPON之间的界面，发现了具有氮和磷浓度梯度的多层马赛克SEI结构，在非晶基质中形成微晶。这种独特的SEI纳米结构小于80 nm，并且稳定且不含任何有机含锂物质或氟化锂成分，与在最先进的有机液体电解质中经常发现的SEI相反。我们的发现揭示了对这类SEI的纳米结构和化学的见解，这些SEI是锂金属电池中稳定锂金属阳极的关键成分。