Effect of temperature on formation and evolution of solid electrolyte interphase on Si@Graphite@C anodes

Abstract Studies on the formation and evolution of the solid electrolyte interface (SEI) film under different ambient temperatures are important to understand the failure behavior of lithium-ion batteries (LIBs). Herein, in-situ electrochemical impedance spectroscopy (EIS) test is performed on the whole discharge process of Si@Graphite@C/Li cell at 0, 25 and 55 ℃, respectively. Combining with scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy characterizations, it is found that the SEI film undergoes a complicated evolution process of pre-formation, self-improvement and gradual decay in succession at 25 ℃. Besides, due to the dissolution of organo-alkyl lithium at high temperature, the formed film is mainly composed of LiF, Li2CO3 and other inorganic salts, which helps to decrease the impedance. However, the electrolyte is consumed continuously on the new exposed interface, leading to the degraded performance of the cell. Moreover, the dynamic properties of Li+ ions are poor at low temperature, though the migration ability of Li+ ions in the solid phase can be improved as the cycle goes on. Therefore, the development and application of in-situ EIS technology are expected to become an important means to explain the electrochemical performance of batteries.