Compatibility of LiMn2O4 cathode with electrolyte based on low-viscosity ether-functionalized pyrazolium ionic liquid
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One new ether-functionalized ionic liquid (IL) composed of pyrazolium cation with one 2-ethoxyethyl group and bis(trifluoromethylsulfonyl)imide anion was synthesized and characterized. The IL showed the lowest viscosity among all the reported pyrazolium ILs, and the value was 38.9 mPa s at room temperature. The conductivity of the IL was 3.48 mS cm−1 at 25 °C, and its electrochemical window was 4.4 V. Cycling performance of symmetric lithium cell was investigated for the IL electrolyte with 0.6 mol kg−1 of LiTFSI. Li/LiMn2O4 cell using the IL electrolyte owned good cycling and rate performances, and it was found for the first time that LiMn2O4 cathode was compatible with electrolyte based on ether-functionalized IL. By the characterizations of X-ray diffraction and scanning electron microscopy for fresh and cycled LiMn2O4 electrodes, it was inferred that the slow dissolution of LiMn2O4 in the IL electrolyte might happen during the charge–discharge processes.
KeywordsIonic liquid Pyrazolium cation Lithium battery Electrolyte
The authors thank the Research Center of Analysis and Measurement of Shanghai Jiao Tong University for the help in NMR characterization. This work is financially supported by the National Natural Science Foundation of China (Grants No. 21103108, 21173148 and 21373136).
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