Effect of Vinylene Carbonate and Fluoroethylene Carbonate on SEI Formation on Graphitic Anodes in Li-Ion Batteries

Mengyun Nie,Julien Demeaux,Brett L Lucht,Arijit Bose,David R Heskett,Yanjing Chen,Benjamin T Young,Joseph C Woicik

doi:10.1149/2.0021513jes

Abstract

Binder free (BF) graphite electrodes were utilized to investigate the effect of electrolyte additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) on the structure of the solid electrolyte interface (SEI). The structure of the SEI has been investigated via ex-situ surface analysis including X-ray Photoelectron spectroscopy (XPS), Hard XPS (HAXPES), Infrared spectroscopy (IR) and transmission electron microscopy (TEM). The components of the SEI have been further investigated via nuclear magnetic resonance (NMR) spectroscopy of D2O extractions. The SEI generated on the BF-graphite anode with a standard electrolyte (1.2 M LiPF6 in ethylene carbonate (EC) / ethyl methyl carbonate (EMC), 3/7 (v/v)) is composed primarily of lithium alkyl carbonates (LAC) and LiF. Incorporation of VC (3% wt) results in the generation of a thinner SEI composed of Li2CO3, poly(VC), LAC, and LiF. Incorporation of VC inhibits the generation of LAC and LiF. Incorporation of FEC (3% wt) also results in the generation of a thinner SEI composed of Li2CO3, poly(FEC), LAC, and LiF. The concentration of poly(FEC) is lower than the concentration of poly(VC) and the generation of LAC is inhibited in the presence of FEC. The SEI appears to be a homogeneous film for all electrolytes investigated.

Highlights

The cell cycled with the standard electrolyte [1.2 M LiPF6/ EC:EMC(3:7 v/v)] has a shoulder at 0.6 V vs. Li/Li+ due to reduction of the electrolyte to generate an Solid Electrolyte Interphase (SEI) resulting in a first cycle efficiency of 76%
The cells cycled with electrolyte containing 3% FEC displayed a lower efficiency (74%) during the first cycle and a new large plateau is observed at 1.0 V vs. Li/Li+ due to reduction of the FEC.[20]
The F 1s X-ray photoelectron spectroscopic (XPS) and Hard X-ray Photoemission Spectroscopy (HAXPES) spectra for the electrode cycled with the standard electrolyte, electrolyte with added FEC and electrolyte with added Vinylene Carbonate (VC) have one main peak assigned to LiF and a second small shoulder which is assigned to LiPF6/LixPFyOz (Figure 4)

Summary

See next page for additional authors

R., Chen, Y., Bose, A., Woicik, J. Effect of Vinylene Carbonate and Fluoroethylene Carbonate on SEI Formation on Graphitic Anodes in Li-Ion Batteries. Authors Mengyun Nie, Julien Demeaux, Benjamin T. Heskett, Yanjing Chen, Arijit Bose, Joseph C. This article is available at DigitalCommons@URI: https://digitalcommons.uri.edu/chm_facpubs/126

JES FOCUS ISSUE ON ELECTROCHEMICAL INTERFACES IN ENERGY STORAGE SYSTEMS

Results and Discussion

Conclusions