Construction of an Inorganic LiF/Li₂S-Rich Solid Electrolyte Interphase Layer on a SiO/C Anode for Low-Temperature Lithium-Ion Batteries

SiO/C composites are widely used as anodes for high-energy-density Li-ion batteries due to their high specific capacity and excellent stability. However, severe performance degradation at lower temperatures postpones their practical applications. In this study, we propose a facile electrolyte-engineered method for the construction of an inorganic salt-rich solid electrolyte interphase (SEI) layer on the SiO/C composite anode for promoting its low-temperature performance. By preprocessing the SiO/C anode in a high-concentration electrolyte, a robust and dense inorganic-rich SEI layer has thus been constructed. Time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy results indicate that an inorganic-rich SEI (H-SEI) forms via a graded distribution of LiF and Li₂S. Electrochemical impedance spectroscopy results demonstrate that H-SEI can accelerate the desolvation of Li-ions at the interface at –20 °C, thereby enhancing the kinetics of electrochemical reactions. The processed SiO/C composite anode illustrates a specific capacity of 354.3 mAh g^–1 after 200 cycles (81.9% retention) in a 1 M-LiFSI cell. Coupled with the LiNi_0.8Co_0.1Mn_0.1O₂ cathode, the full cell with H-SEI delivers a specific capacity retention ratio of 82.9% after 200 cycles at –20 °C, whereas the full cell without H-SEI demonstrates a capacity retention rate of only 35.1%. This work provides new insights into constructing robust inorganic-rich SEI layers by the low-cost method of high-salt processing and low-salt cycling for advanced silicon-based anodes.