How to improve the lithium ion battery performance especially the cycle stability under the premise of the existing electrode material system of the lithium ion battery is the focus and the hot spot in the world at present. The solid electrolyte interface membrane, ie sei (solidelectrolyteteinterface) membrane, is the first (or previous) charge-discharge process of the liquid electrolyte lithium-ion battery. The electrode material reacts with the electrolyte at the solid-liquid interface to form a protective layer , A passivation interface layer with solid electrolyte features covering the surface of the electrode material (especially the negative electrode). Although different electrolytes can greatly affect the performance of the battery, the intrinsic mechanism of the sei membrane structure formed by different electrolytes, the relationship between the chemical composition and the battery has long been neglected due to the lack of effective research methods. Recently, Dr. Shen Cai and his team at the New Energy Institute under the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS) have recently conducted a real-time study using ethylene carbonate (ec) and fluorocarbonate (fec) as the basis for in situ electrochemical atomic force microscopy Electrolyte sei film growth process and found that the sei film formed by these two electrolytes in the film formation potential, compactness, stability and thickness of the significant difference, combined with xps spectral analysis, the researchers found that fec electrolyte formed sei membrane contains more lif inorganic salt, lif has a good hardness and stability, combined with the dense sei film thereby explaining the mechanism of fec electrolyte film forming stability. The findings were published in the journal Acsappliedmaterials & interfaces of the American Chemical Society (2015,7,25441-25447). Electrochemical Atomic Force Microscopy combined with spectroscopy, is expected to become a lithium-ion battery electrolyte and additive film forming mechanism of a powerful means to speed up the optimization of various electrolytes and additives screening process. The above work has been funded by the National Natural Science Foundation of China and the Youth Innovation Promotion Association of Chinese Academy of Sciences.