电解液组成对尖晶石LiMn_2O_4中锂离子嵌脱过程的影响

运用电化学阻抗谱(EIS)研究了尖晶石LiMn2O4正极在1mol·L-1LiPF6-EC(碳酸乙烯酯)∶DEC(碳酸二乙酯)∶DMC(碳酸二甲酯),1mol·L-1LiPF6-EC∶DEC∶EMC(碳酸甲乙酯)和1mol·L-1LiPF6-EC∶DMC三种不同电解液中,-20-20℃范围内的阻抗谱特征随温度的变化.研究结果表明,温度强烈影响尖晶石LiMn2O4正极的阻抗谱特征,而电解液组成对尖晶石LiMn2O4正极阻抗谱特征的影响较小,但电解液组成对锂离子在尖晶石LiMn2O4正极中嵌入脱出过程相关动力学参数影响较大.测得尖晶石LiMn2O4正极在上述三种电解液中,锂离子迁移通过固体电解质相界面(SEI)膜的离子跳跃能垒平均值分别为7.60、16.40和18.40kJ·mol-1;电子电导率的热激活化能平均值分别为44.77、35.47和68.06kJ·mol-1;嵌入反应活化能平均值分别为52.19、46.19和69.86kJ·mol-1.

Influence of Electrolyte Composition on the Intercalation-Deintercalation Process of Lithium Ion in Spinel LiMn2O4

Variations in the impedance spectra of the commercially available spinel LiMn2O4 electrode from -20 to 20 ℃ were investigated by electrochemical impedance spectroscopy (EIS) in 1 mol·L-1 LiPF6-EC (ethylene carbonate)|DEC (diethyl carbonate)|DMC (dimethyl carbonate), 1 mol·L-1 LiPF6-EC|DEC|EMC (ethyl methyl carbonate) and 1 mol·L -1 LiPF6-EC |DMC electrolyte solutions. We found that the impedance spectral characteristics of the spinel LiMn2O4 electrode was strongly influenced by temperature and only slightly influenced by the electrolyte composition. However, the electronic resistance and the resistance of the SEI filmas well as the charge transfer reaction resistance of the spinel LiMn2O4 electrode were strongly influenced by the electrolyte composition. In 1 mol·L-1 LiPF6-EC|DEC|DMC, 1 mol·L-1 LiPF6-EC|DEC|EMC and 1 mol·L-1 LiPF6-EC|DMC electrolyte solutions, the energy barriers for the ion jump relating to the migration of lithium ions through the solid electrolyte interphase (SEI) film of the spinel LiMn2O4 electrode were determined to be 7.60, 16.40, and 18.40 kJ·mol-1. The thermal active energies of the electronic conductivities were 44.77, 35.47, and 68.06 kJ·mol-1 and the intercalation-deintercalation reaction active energies were 52.19, 46.19, and 69.86 kJ·mol-1, respectively.