FEC与VC在锂离子电池石墨负极界面行为研究

doi:10.19799/j.cnki.2095-4239.2025.0217

摘要/Abstract

摘要：

在锂离子电池中，电解液添加剂如氟代碳酸乙烯酯(FEC)和碳酸亚乙烯酯(VC)被广泛用于改善电极/电解液界面的稳定性，但是其对石墨电极表面的作用机制仍不清晰。本工作系统研究了FEC和VC在锂离子电池石墨电极上的界面行为。通过循环伏安法、电化学阻抗谱、扫描电子显微镜、透射电子显微镜和X射线光电子能谱等多种表征手段，揭示了FEC和VC在石墨电极表面的差异化作用机制。电化学阻抗结果显示Li|Gr电池中FEC形成固体电解质界面(SEI)前后的总阻抗小于VC，Li|Ref|Gr电池中FEC形成SEI前后的总阻抗大于VC。通过电化学阻抗谱-弛豫时间分布(EIS-DRT)方法，进一步对界面阻抗进行剖析，确定了FEC和VC在Li|Gr电池中的SEI阻抗、SEI-Gr界面电荷交换阻抗、SEI-电解液界面电荷交换阻抗的特征弛豫时间范围，FEC与VC各部分的弛豫时间基本一致，SEI阻抗、SEI-Gr界面电荷交换阻抗、SEI-电解液界面电荷交换阻抗弛豫时间分别为5E-5 s、3E-4 s、5E-3 s。研究结果表明，VC在0.77 V还原形成富含有机物的SEI，可显著降低石墨界面的阻抗，但其与锂金属的相容性较差，导致电池总阻抗增加。而FEC在1 V电压下还原，在石墨表面形成富含LiF的SEI，虽然使得石墨界面阻抗增加，但是显著优化了锂金属对电极的稳定性。FEC对石墨界面的劣化影响小于对锂金属的稳定优势，使得电池总阻抗最小。本研究为锂离子电池电解液的优化设计提供了重要的实验技术和理论指导。

关键词: 锂离子电池, 电极/电解液界面, 氟代碳酸乙烯酯, 碳酸亚乙烯酯

Abstract:

In lithium-ion batteries, electrolyte additives such as fluorinated ethylene carbonate (FEC) and vinylene carbonate (VC) have been widely employed to enhance the stability of the electrode/electrolyte interface; however, their effects on graphite electrodes remain unclear. In this study, the interfacial behavior of FEC and VC on graphite anodes in lithium-ion batteries is systematically investigated. The distinct mechanisms by which FEC and VC influence graphite surfaces are elucidated through various characterization techniques, including cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical impedance results indicate that, in Li|Gr cells, the total impedance before and after solid electrolyte interphase (SEI) formation with FEC is lower than that with VC, whereas in Li|Ref|Gr cells, the total impedance with FEC is higher than that with VC. The interfacial impedances are further deconvoluted using the electrochemical impedance spectroscopy-distribution of relaxation time (EIS-DRT) method to determine the SEI impedance, the charge-exchange impedance at the SEI-graphite interface, and the SEI–electrolyte interface charge-exchange impedance in Li|Gr cells. The characteristic relaxation times of FEC and VC are essentially consistent for each component, with values of 5×10^-5 s for SEI impedance, 3×10^-4 s for SEI-graphite interface charge exchange, and 5×10^-3 s for SEI-electrolyte interface charge exchange. The results show that VC reduction at 0.77 V forms an organic-rich SEI, significantly reducing impedance at the graphite interface but exhibiting poor compatibility with lithium metal, thereby increasing the total cell impedance. In contrast, FEC reduction at 1 V forms a LiF-rich SEI on the graphite surface, which increases graphite interface impedance yet greatly improves the stability of the lithium metal electrode. The adverse effect of FEC on the graphite interface is outweighed by its stabilizing effect on lithium metal, ultimately reducing the total cell impedance. This study provides important experimental insights and theoretical guidance for the optimized design of electrolytes in lithium-ion batteries.

Key words: lithium-ion battery, electrode/electrolyte interface, fluorinated ethylene carbonate, vinylidene carbonate

中图分类号:

TQ 021.9

赵岩, 刘浩, 易宗琳, 李莉, 谢莉婧, 苏方远. FEC与VC在锂离子电池石墨负极界面行为研究[J]. 储能科学与技术, 2025, 14(9): 3249-3258.

Yan ZHAO, Hao LIU, Zonglin YI, Li LI, Lijing XIE, Fangyuan SU. Interfacial behavior of FEC and VC at graphite anode of lithium-ion batteries[J]. Energy Storage Science and Technology, 2025, 14(9): 3249-3258.

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组分	EC	DMC	FEC	VC	LiPF₆
HOMO	-8.46	-8.22	-7.39	-8.97	-6.20
LUMO	-0.28	-0.07	-0.61	-0.39	-1.77