How to improve the performance of lithium ion battery, especially its cycling stability, is the focus and focus of research in the world.
The solid electrolyte interface film (SEI) 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 layer having Protection function, a passivation interface layer with a solid electrolyte characteristic covering the surface of the electrode material (especially the negative electrode). Although different electrolytes can influence the performance of the battery to a great extent, the inherent mechanism that the structure of the SEI membrane formed by different electrolytes, the chemical composition, and the battery has long been neglected due to the lack of effective research methods.
Dr. Shen Cai and his research team of the Institute of Materials Science and Engineering of the Ningbo Institute of Materials Science and Engineering, Chinese Academy of Sciences, recently researched the use of in situ electrochemical atomic force microscopy (AFM) as the basis for the study of ethylene carbonate (EC) and fluoroethylene carbonate (FEC). During the growth of the electrolyte SEI film, it was found that the SEI films formed by these two electrolytes differ significantly in filming potential, compactness, stability, and thickness. In combination with XPS spectral analysis, the researchers found that the FEC electrolyte formed The SEI film contains more LiF inorganic salts. Because LiF has better hardness and stability, the compactness of the SEI film is combined to explain the mechanism of film formation stability of the FEC electrolyte. The results of this study were published in the journal ACS Applied Materials & Interfaces (2015, 7, 25441-25447).
Electrochemical atomic force microscopy (AFM) combined with spectroscopy technology is expected to be a powerful characterization method for the formation of electrolytes and additives for Li-ion batteries, and to speed up the optimization of various electrolytes and additives.
The above work was funded by the National Natural Science Foundation Youth Project and the Young Innovation Promotion Association of the Chinese Academy of Sciences.
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