LiODFB基电解液的电化学性能及其与钛酸锂的相容性研究

doi:10.3724/SP.J.1077.2013.12316

摘要/Abstract

摘要：

采用电化学工作站测试了1 mol/L LiODFB (LiPF₆) EC+DMC+EMC(1:1:1 质量比)电解液的热稳定性及其对铝箔集流体的腐蚀性, 测试了LTO/Li电池的CV曲线及EIS图谱, 并采用电池性能测试系统测试电池的倍率性能和循环性能, 探索LiODFB电解液与LiFePO₄/LTO电极的相容性。结果表明: 在室温和60℃条件下, LiODFB电解液及其对铝箔的稳定性均优于LiPF₆电解液, 以LiODFB和LiPF₆为电解液的LTO/Li电池的CV曲线都具有单一的氧化还原峰, 且其首次充放曲线均具有稳定的充放电平台, 室温时以LiFePO₄/LTO为电极的LiODFB电池和LiPF₆电池在0.5C和1C倍率的电池性能相差不大; 室温和60℃时LiODFB电池的循环性能均优于LiPF₆电池, 60℃时尤为显著。

关键词: 草酸二氟硼酸锂, 钛酸锂, 电化学性能, 锂离子电池

Abstract:

1 mol/L LiODFB (LiPF₆) EC+DMC+EMC (1:1:1 (wt%)) electrolyte’s thermal stability and corrosivity to the aluminum foil were tested by the electrochemical workstation. Cyclic voltammogram, electrochemical impedance spectroscopy rate and cycle performances of LTO/Li battery were measured. The compatibility between LiFePO₄/LTO electrode and electrolyte was studied. Results show that at room temperature and 60℃, the stability of LiODFB electrolyte and its corrosivity to the aluminum foil are superior to that of LiPF₆ electrolyte. LTO/Li cells with either LiODFB or LiPF₆ for electrolyte have simple REDOX peak, and their first charge-discharge curves have stable charge-discharge platform. The difference battery performance between LiODFB and LiPF₆ with LiFePO₄/LTO as electrode at 0.5C and 1C rates is not significant at room temperature. LiODFB battery exhibits better cycle performance than LiPF₆ battery at room temperature and especially at 60℃.

Key words: lithium di?uoro(oxalato)borate, lithium titanate, electrochemical performance, lithium battery

中图分类号:

TM911

周宏明, 刘芙蓉, 李荐, 方珍奇, 李艳芬, 朱玉华. LiODFB基电解液的电化学性能及其与钛酸锂的相容性研究[J]. 无机材料学报, 2013, 28(5): 507-514.

ZHOU Hong-Ming,LIU Fu-Rong, LI Jian, FANG Zhen-Qi, LI Yan-Fen, ZHU Yu-Hua. Research on the LiODFB Electrolyte’s Electrochemical Performance and Its Compatibility with LTO Electrode[J]. Journal of Inorganic Materials, 2013, 28(5): 507-514.

图/表 10

图1 电解液的电流-电位曲线

Fig. 1 I-E curves of electrolytes

图2 电解液对集流体铝箔的电流-电位曲线

Fig. 2 I-E curves of aluminum foil in electrolytes

图3 LiODFB作为LTO/Li电池电解液在不同温度下的循环伏安曲线

Fig. 3 CV curves of LTO/Li cells with LiODFB electrolyte at different temperatures

图4 LiODFB作为LiFePO4/LTO电池电解液在不同温度下的首次充放电曲线

Fig. 4 Initial charge-discharge curves of LiFePO4/LTO cells with LiODFB electrolyte at different temperatures

图5 LiODFB作为LiFePO4/LTO电池电解液在不同倍率的循环性能曲线

Fig. 5 Cycle performance of LiFePO4/LTO cells with LiODFB electrolyte at different rates

图6 LiODFB作为LiFePO4/LTO电池电解液在不同温度的循环性能曲线

Fig. 6 Cycle performance of LiFePO4/LTO batteries with LiODFB electrolyte at different temperatures

图7 LiODFB作为LTO/Li电池电解液在不同温度循环前后的交流阻抗图谱

Fig. 7 Electrochemical impedance spectra of LTO/Li cell with LiODFB electrolyte before and after cycling

图8 电解液体系的等效电路图

Fig. 8 Equivalent circuit of AC impedance for electrolyte

Table 1 Electrochemical impedance of LiODFB or LiPF6 at different temperatures

Situation	R_L(LiODFB)/Ω	R_L(LiBF6)/Ω	R_ct(LiODFB)/Ω	R_ct(LiBF6)/Ω
25℃ before cycling	10.80	24.9	341.9	278.70
25℃ after cycling	15.30	45.2	367.9	348.70
60℃ before cycling	6.58	4.6	34.2	43.06
60℃ after cycling	9.80	27.9	57.2	64.50

图9 LiFePO4/LTO电池循环前后LiFePO4极片的SEM照片

Fig. 9 SEM images of LiFePO4 electrode from LiFePO4/LTO cells before and after cycling

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