In Situ/ex Situ Investigations on the Formation of the Mosaic Solid Electrolyte Interface Layer on Graphite Anode for Lithium-Ion Batteries

In the ongoing pursuit toward a high-performance lithium-ion battery (LIB), an understanding of the solid electrolyte interface (SEI) layer is important to enhance the performance and lifetime of LIB. Despite many years of dedicated research on the study of the SEI layer, the well-known mosaic model of the SEI layer has not yet been fully established experimentally. Herein, we report a comprehensive experimental evidence of the formation and growth process of the mosaic structure of the SEI layer by using a specially designed cell. Sequential in situ and ex situ characterizations provide experimental evidence for the mosaic structure of the SEI layer. Our experimental characterizations open up a promising approach to investigate the electrode–electrolyte interface comprehensively in advanced battery systems.