VC和FEC在硅负极界面的特性
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摘要
用电化学循环伏安测试、电化学阻抗测试和X射线光电子能谱(XPS)分析研究硅负极在不含添加剂和含2%氟代碳酸乙烯酯(FEC)、2%碳酸亚乙烯酯(VC)的1 mol/L Li PF_6/EC+DMC+EMC(体积比1∶1∶1) 3种电解液中的电化学性能及固体电解质相界面(SEI)膜的组成。在含2%FEC的电解液中,硅负极的首次充放电效率最高,为77. 9%;阻抗最小,因为电极表面形成了Li F和碳酸锂组成的稳定SEI膜;在含2%VC的电解液中,硅负极的比容量最低,为525. 09 mAg/g;阻抗最高,为电极表面形成较厚的含碳酸锂、微量LiF及Li_xPF_yO_z的SEI膜。
Cyclic voltammetry,electrochemical impedance testing and X-ray photoelectron spectroscopy( XPS) analysis were used to study Si anodes at 1 mol/L Li PF_6/EC + DMC + EMC( volume ratio 1∶ 1∶ 1). Electrochemical performance and solid electrolyte phase interface( SEI) film composition of three electrolyte systems containing no additives,2% fluoroethylene carbonate( FEC) and2% vinylene carbonate( VC). Among the electrolytes containing 2% FEC,the Si anode had the highest initial charge and discharge efficiency and the lowest impedance. The surface of the electrode formed a stable SEI film composed of Li F and lithium carbonate; in the electrolyte containing 2% VC,Si anode had the lowest specific capacity and the highest impedance,and a thick SEI film containing lithium carbonate,a trace amount of Li F and LixPFyOzwas formed on the surface of the electrode.
Cyclic voltammetry,electrochemical impedance testing and X-ray photoelectron spectroscopy( XPS) analysis were used to study Si anodes at 1 mol/L Li PF_6/EC + DMC + EMC( volume ratio 1∶ 1∶ 1). Electrochemical performance and solid electrolyte phase interface( SEI) film composition of three electrolyte systems containing no additives,2% fluoroethylene carbonate( FEC) and2% vinylene carbonate( VC). Among the electrolytes containing 2% FEC,the Si anode had the highest initial charge and discharge efficiency and the lowest impedance. The surface of the electrode formed a stable SEI film composed of Li F and lithium carbonate; in the electrolyte containing 2% VC,Si anode had the lowest specific capacity and the highest impedance,and a thick SEI film containing lithium carbonate,a trace amount of Li F and LixPFyOzwas formed on the surface of the electrode.
引文
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[7] CHEN L B,WANG K,XIE X H,et al. Enhancing electrochemical performance of silicon film anode by vinylene carbonate electrolyte additive[J]. Electrochem Solid-State Lett,2006,9:A512-A515.