Experimental and Theoretical Insights into Factors Improving the Performance of Li-ion Batteries with a Si-based Anode by 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropyl Ether as an Additive

Anodes containing Si and SiOx are promising candidates for the fabrication of high energy density Li-ion batteries (LIBs).However, despite their specific capacity advantages, maintaining a sustainable cycling performance remains challenging due to their significant volume expansion and contraction.To enhance the interfacial stability of SiOx, this study uses an electrolyte containing 1,1,2,2-tetrafluoroethyl-2,2,3,3tetrafluoropropyl ether (D2) as an electrolyte additive and focuses on the solid electrolyte interphase (SEI) formed on the electrode surface.The reduction of D2 forms a robust LiFbased SEI along with a D2-specific fluoroalkyl component, which sufficiently stabilizes the SiOx interface.Therefore, the electrolyte containing D2 contributes not only to improving the charge-discharge cycle life and reducing resistance but also to suppressing gas generation within the battery system.To elucidate the mechanism of performance enhancement by D2, this study employs a wide range of analytical techniques, such as AC impedance spectroscopy, scanning electron microscopy (SEM), energy dispersive Xray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (TOF-SIMS), along with density functional theory (DFT) calculations to predict the reaction pathways of D2.These experimental and theoretical analyses demonstrate that D2 is an excellent additive for anode materials ACCEPTED MANUSCRIPT 4 containing SiOx.