Li鈥揙2 Battery Degradation by Lithium Peroxide (Li2O2): A Model Study

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• 作者：Reza Younesi ; Maria Hahlin ; Fredrik Bj枚refors ; Patrik Johansson ; Kristina Edstr枚m
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：January 8, 2013
• 年：2013
• 卷：25
• 期：1
• 页码：77-84
• 全文大小：588K
• 年卷期：v.25,no.1(January 8, 2013)
• ISSN：1520-5002

文摘

The chemical stability of the Li鈥揙₂ battery components (cathode and electrolyte) in contact with lithium peroxide (Li₂O₂) was investigated using X-ray photoelectron spectroscopy (XPS). XPS is a versatile method to detect amorphous as well as crystalline decomposition products of both salts and solvents. Two strategies were employed. First, cathodes including carbon, 伪-MnO₂ catalyst, and Kynar binder (PVdF-HFP) were exposed to Li₂O₂ and LiClO₄ in propylene carbonate (PC) or tetraethylene glycol dimethyl ether (TEGDME) electrolytes. The results indicated that Li₂O₂ degrades TEGDME to carboxylate containing species and that the decomposition products, in turn, degraded the Kynar binder. The 伪-MnO₂ catalyst was unaffected. Second, Li₂O₂ model surfaces were kept in contact with different electrolytes to investigate the chemical stability and also the resulting surface layer on Li₂O₂. Further, the XPS experiments revealed that the Li salts such as LiPF₆, LiBF₄, and LiClO₄ decomposed to form LiF or LiCl together with P鈥揙 or B鈥揙 bond containing compounds when exposed to Li₂O₂. PC decomposed to carbonate and ether based species. The degradation of the electrolytes increased from short to long exposure time indicating that the surface layer on Li₂O₂ became thicker by increasing time. Overall, it was shown that a mixture of ethylene carbonate and diethyl carbonate (EC/DEC) is more robust in contact with Li₂O₂ compared to PC.

Keywords:

lithium鈭抋ir battery; chemical decomposition; Li₂O₂; X-ray photoelectron spectroscopy; lithium鈭抩xygen; lithium peroxide; XPS