塑晶基离子液体合成及其电化学性能

通过简单、易于工业化的重结晶方法制备了高纯1-甲基-1-乙基吡咯烷鎓双(三氟甲基磺酰)亚胺盐(P₁₂TFSI)塑晶化合物. 在此化合物中加入30% (摩尔分数, x)双(氟磺酰)亚胺锂(LiFSI)后, 得到P₁₂TFSI/LiFSI 塑晶基离子液体. 采用循环伏安法、恒电压极化法及恒电流充放电法等电化学方法考察了该离子液体的电化学窗口、铝箔集流体的腐蚀性及电池性能. 结果表明, 该离子液体电解质具有5.00 V的电化学窗口, 室温离子电导率达到0.92 mS·cm^-1, 且不腐蚀Al 集流体. 以该塑晶离子液体作为电解液组装的实验电池LiCoO₂/Li 表现出良好的充放电特性及循环性能, 在较低倍率下能够和使用碳酸酯类电解液组装的实验电池的性能相媲美. 在4.50 V高电压下, 循环20周后, 容量仍能保持在175 mAh·g^-1, 容量保持率为95.1%. 这些结果说明该离子液体在高性能锂二次电池中具有良好的应用前景.

Synthesis and Electrochemical Performance of Plastic Crystal Compound-Based Ionic Liquid

Highly pure plastic crystal, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (P₁₂TFSI), was synthesized and purified by an easily industrializable recrystallization method. The P₁₂TFSI/LiFSI ionic liquid was obtained by mixing P₁₂TFSI with 30% (molar fraction, x) LiFSI. Electrochemical characterization methods including cyclic voltammetry, constant voltage polarization and charge/discharge at constant current were used to investigate the electrochemical window, stability vs Al corrosion, and battery performance of the ionic liquid.Awide electrochemical window of 5.00 V, non-corrosion of theAl current collector, and 0.92mS·cm^-1 of ionic conductivity at room temperature were observed. LiCoO₂/Li batteries assembled using this ionic liquid electrolyte showed good charge-discharge characteristics and cycle performance, comparable with those of carbonate-based electrolyte at low rate. The specific capacity of the LiCoO₂ remained 175 mAh·g^-1 after 20 cycles (95.1% capacity retention) despite cycling at a high voltage up to 4.50 V. These results indicate that the plastic crystal-based ionic liquid P₁₂TFSI/LiFSI could be potentially applied in high-energy density lithium secondary batteries.