Effect of Fluoroethylene Carbonate on Solid Electrolyte Interphase Formation of the SiO/C Anode Observed by In Situ Atomic Force Microscopy

Silicon oxide-based materials are promising anode materials for the real application in lithium-ion batteries. The solid electrolyte interphase is vital for the cyclability and rate capability of the electrode material. Here, in this study, the effect of fluoroethylene carbonate (FEC) as the well-known electrolyte additive on the interface film formation of the commercial SiO/C anode was investigated. The potential-dependent morphology of the SEI layer were obtained via in situ atomic force microscopy (AFM) for the first two cycles and ex situ AFM for the 10th, 30th, and 50th cycles. The morphology analysis was complemented by the chemical composition evolution by ex situ X-ray photoelectron spectroscopy and Young’s modulus calculation via PeakForce quantitative nanomechanical mapping of AFM. The results indicated a dense, compact, and stiff SEI layer on the surface of SiO/C in FEC-based electrolyte, in contrast to the scattered and thin SEI layer in ethylene carbonate-based electrolyte.