Increasing the Affinity Between Carbon-Coated LiFePO4/C Electrodes and Conventional Organic Electrolyte by Spontaneous Grafting of a Benzene-Trifluoromethylsulfonimide Moiety

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• 作者：Nicolas Delaporte ; Alexis Perea ; Estelle Leb猫gue ; S茅bastien Ladouceur ; Karim Zaghib ; Daniel B茅langer
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：August 26, 2015
• 年：2015
• 卷：7
• 期：33
• 页码：18519-18529
• 全文大小：571K
• ISSN：1944-8252

文摘

The grafting of benzene-trifluoromethylsulfonimide groups on LiFePO₄/C was achieved by spontaneous reduction of in situ generated diazonium ions of the corresponding 4-amino-benzene-trifluoromethylsulfonimide. The diazotization of 4-amino-benzene-trifluoromethylsulfonimide was a slow process that required a high concentration of precursors to promote the spontaneous grafting reaction. Contact angle measurements showed a hydrophilic surface was produced after the reaction that is consistent with grafting of benzene-trifluoromethylsulfonimide groups. Elemental analysis data revealed a 2.1 wt % loading of grafted molecules on the LiFePO₄/C powder. Chemical oxidation of the cathode material during the grafting reaction was detected by X-ray diffraction and quantified by inductively coupled plasma atomic emission spectrometry. Surface modification improves the wettability of the cathode material, and better discharge capacities were obtained for modified electrodes at high C-rate. In addition, electrochemical impedance spectroscopy showed the resistance of the modified cathode was lower than that of the bare LiFePO₄/C film electrode. Moreover, the modified cathode displayed superior capacity retention after 200 cycles of charge/discharge at 1 C.