Synergistic film-forming effect of oligo(ethylene oxide)-functionalized trimethoxysilane and propylene carbonate electrolytes on graphite anode

Abstract

Oligo(ethylene oxide)-functionalized trialkoxysilanes can be used as novel electrolytes for high-voltage cathode, such as LiCoO2 (4.35 V) and Li1.2Ni0.2Mn0.6O2 (4.6 V); however, they are not well compatible with graphite anode. In this study, a synergistic solid electrolyte interphase (SEI) film-forming effect between [3-[2-(2-methoxyethoxy)ethoxy]propyl]-trimethoxysilane (TMSM2) and propylene carbonate (PC) on graphite electrode was investigated. Excellent SEI film-forming capability and cycling performance was observed in graphite/Li cells using the electrolyte of 1 M LiPF6 in the binary solvent of TMSM2 and PC, with the PC content in the range of 10–30 vol.%. Meanwhile, the graphite/Li cells delivered higher specific capacity and better capacity retention in the electrolyte of 1 M LiPF6 in TMSM2 and PC (TMSM2:PC = 9:1, by vol.), compared with those in the electrolyte of 1 M LiPF6 in TMSM2 and EC (TMSM2:EC = 9:1, by vol.). The synergistic SEI film-forming properties of TMSM2 and PC on the surface of graphite anode was characterized by electrolyte solution structure analysis through Raman spectroscopy and surface analysis detected by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) analysis.