期刊
ACS APPLIED MATERIALS & INTERFACES
卷 11, 期 15, 页码 14066-14075出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.8b22221
关键词
solid electrolyte interface; fluoroethylene carbonate; solid-state NMR; XPS; X-PEEM
资金
- National Key Research and Development Program of China
- National Natural Science Foundation of China
Silicon-based anodes have the potential to be used in next generation lithium ion batteries owing to their higher lithium storage capacity. However, the large volume change during the charge/discharge process and the repeated formation of a new solid electrolyte interface (SEI) on the re-exposed Si surface should be overcome to achieve a better electrochemical performance. Fluoroethylene carbonate (FEC) has been widely used as an electrolyte additive for Si-based anodes, but the intrinsical mechanism in performance improvement is not clear yet. Here, we combined solid-state NMR, X-ray photoelectron spectroscopy, and Xray photoemission electron microscopy to characterize the composition, structure, and inhomogeneity of the SEI on Si/C composite anodes with or without the FEC additive. Similar species are observed with two electrolytes, but a denser SEI formed with FEC, which could prevent the small molecules (i.e., LiPF6, P-O, and Li-O species) from penetrating to the surface of the Si/C anode. The hydrolysis of LiPF6 leading to LixPOyFz and further to Li3PO4 could also be partially suppressed by the denser SEI formed with FEC. In addition, a large amount of LiF could protect the cracking and pulverization of Si particles. This study demonstrates a deeper understanding of the SEI formed with FEC, which could be a guide for optimizing the Si-based anodes for lithium ion batteries.
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