NMR study of the polyethylene glycol diacrylate-LiBF4-1-butyl-3-methylimidazolium tetrafluoroborate-propylene/ethylene carbonate electrolyte system

Abstract

The 1-butyl-3-methylimidazolium tetrafluoroborate-propylene carbonate-ethylene carbonate system in a reticular polymer electrolyte based on polyethylene glycol diacrylate and LiBF4 was studied by high-resolution and pulsed field gradient NMR. The 1H, 13C, 7Li, and 19F NMR spectra of the electrolyte systems were analyzed. During the electrolyte synthesis, propylene undergoes structural changes in the ionic liquid, which adversely affects the ion conductivity (the maximum conductivity in this system is 8.46 × 10−4 S/cm at 20°C) and the self-diffusion coefficients of the lithium ions. When the propylene carbonate content in the polymer electrolyte increased from 15 to 32 wt %, the proportion of lithium ions with a high self-diffusion coefficient (10−11 m2/s) decreased from 24 to 7%. In the case of ethylene carbonate, this effect was less pronounced, the conductivity in these systems reaching 2.46 × 10−3 S/cm at 20°C. The high-resolution NMR study did not reveal any structural changes in the ionic liquid and ethylene carbonate during the modeling of radical polymerization.