Anisotropic lithium-ion migration and electro-chemo-mechanical coupling in Sb₂Se₃ single crystals

Harvesting the promising high energy density of advanced electrode materials in lithium-ion batteries is critically dependent on a mechanistic understanding on how the materials function and degrade along with the battery cycling. Here, we tracked phase transformations during (de)lithiation of Sb₂Se₃ single crystals using in situ high-resolution transmission electron microscopy (HRTEM) technique, and revealed electro-chemo-mechanical evolution at the reaction interface. The effect of this electro-chemo-mechanical coupling has a complicated interplay on the lithiation kinetics and causes various types of defects at the reaction front, including dislocation dipoles, antiphase boundaries, and cracks. In return, the formed cracks and related defects build a path for fast diffusion of lithium ions and trigger a highly anisotropic lithiation at the twisted reaction front, giving rise to the formation of presumably “dead” Sb₂Se₃ nanodomains in amorphous Li_xSb₂Se₃. The detailed mechanistic understanding may facilitate the rational design of high-capacity electrode materials for battery applications.