Staining light elements for X-ray imaging

Light elements possess exceptional gravimetric energy densities and underpin a wide range of applications in materials chemistry and biology. Imaging low-atomic-number materials can reveal how function emerges from complex systems. X-ray imaging is a powerful technique to characterize thousands of samples in unbiased ways but it’s insensitive to light elements due to the weak X-ray attenuation. Here, we first develop a selectively staining strategy to transform light, low-X-ray-contrast elements into heavy, X-ray visible compositions while preserving their original structures. As a proof of concept, electrochemically isolated lithium is converted into a high-contrast phase through zinc (Zn) staining via spontaneous Zn2+-Li displacement reactions, overcoming the fundamental limitations of conventional X-ray computed tomography imaging. This method allows for accurate identification and characterization of “isolated” lithium with chemical specificity and voxel-level resolution, revealing how its spatial distribution varies across different electrolytes and explaining distinct failure mechanisms in lithium metal batteries under different electrolyte chemistries. More broadly, our study establishes a versatile diagnostic platform for mechanistic insight and dynamic evolution studies of light-element materials.