化学
电解质
电化学
锂(药物)
无机化学
石墨
碳酸二甲酯
介电谱
碳酸乙烯酯
电导率
插层(化学)
催化作用
电极
有机化学
物理化学
内分泌学
医学
作者
Weidong Lu,Kai Xie,Zhongxue Chen,Yi Pan,Chun Man Zheng
标识
DOI:10.1016/j.jfluchem.2014.02.006
摘要
In this work, a series of trifluoroethyl aliphatic carboxylates with different carbon-chain lengths in acyl group are prepared and investigated as the co-solvents for the carbonate-based electrolyte of lithium-ion batteries. The trifluoroethyl aliphatic carbonates are synthesized by a modified one-step approach, using aliphatic carboxylic acid and trifluoroethanol as the raw materials (molar ratio, 1.2:1), hydrogen ion exchange resin as the catalyst and silica gel drier as the de-hydration. The structure and electrochemical properties of the final products have been characterized by FTIR, 1H NMR, GC–MS, viscosity, conductivity meter and electrochemical measurements. The structure characterizations show that the final products have high purity. Electrochemical tests present that the co-solvents are able to improve the electrochemical performances of graphite electrode at low temperature. In particular, we find that an addition of trifluoroethyl n-hexanoate (TFENH) into 1 M LiPF6/EC + EMC electrolyte can significantly decrease the Li de-intercalation potential of graphite by 540 mV and achieve a high capacity retention of 92% at 218 K. The electrochemical impedance spectroscopy (EIS) measurements indicate that the observed performance improvement at low temperature is associated with the decreased surface film resistance (RSEI) by the addition of co-solvents.
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