January 30, 2025
Journal Article
Direct in situ measurements of electrical properties of solid–electrolyte interphase on lithium metal anodes
Abstract
Solid electrolyte interphase (SEI) critically governs the performance of rechargeable batteries. An ideal SEI is expected to be electrically insulative to prevent persistently parasitic reactions between the electrode and the electrolyte, while ionically conductive to facilitate Faradaic reactions of the electrode. However, the true nature of electrical properties of an SEI layer remains hitherto unclear due to the lack of a direct characterization method. Here, we use in situ bias transmission electron microscopy to directly measure the electrical properties of SEIs formed on copper (Cu) and lithium (Li) substrates. We discover that SEI is distinctively different from a typical electrical insulator. Rather, SEI shows voltage-dependent differential conductance. A higher rate of differential conductance induces a thicker SEI with intricate topographic feature, consequently leading to an inferior Coulombic efficiency and cycling stability. The work provides insight for targeted design of SEI with desired characteristics towards better battery performance.Published: January 30, 2025