an electrochemical storage device adaptable to a multitude of applications (e.g. vehicles, personal electronics, grid balancing). They conventionally use a liquid organic electrolyte containing flammable organic solvents. To promote safer design, the organic electrolyte can be replaced with a nonflammable solid polymer electrolyte (SPE). SPEs offer enhanced safety, low ionic conductivity relative to liquid electrolytes; consequently, incorporating advantageous filler materials to increase solid electrolyte conductivity is paramount. Room temperature ionic liquids (RTILs) are salts that—due to their large and asymmetric ions—are liquid at ambient temperatures. RTILs promote ion transport and reduce polymer crystallinity, making them a promising additive for solid polymer-based electrolytes. are a quasi-solid electrolyte produced from a UV-cured, crosslinking monomer and room temperature ionic liquid mixture. The resulting nonflammable polymer matrix encapsulates and immobilizes the RTIL, producing a high-conductivity, gel-like, solid electrolyte. Poly(ethylene glycol) diacrylate (PEGDA) is a cost-effective crosslinking polymer with a wide voltage stability window and mechanical properties. Independently it has a low ionic conductivity; however, the addition of lithium salt and plasticizers enhances the ionic conductivity significantly. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is a lithium salt soluble in PEGDA that provides lithium ions, intrinsically improving the electrolyte’s ionic conductivity. Plasticizers function through promoting the amorphous phase of polymers—providing flexibility for the PEGDA matrix and further increasing the conductivity. Within the scope of this study, two plasticizers were examined: succinonitrile (SCN) and the RTIL, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([BMPyrr][TFSI]). SCN is a cost-effective plasticizer with moderate ion conductivity. Contrastingly, [BMPyrr][TFSI] is an expensive plasticizer with high ion conductivity This study examines and characterizes the synergistic interaction between SCN and [BMPyr][TFSI] in an optimized ionogel. Electrolyte performance was measured through ionic conductivity calculations and lithium iron phosphate (LFP) half-cell cycling capabilities. The ionic conductivities of electrolytes containing SCN and RTIL were measured at [0, 10, 20, 30, 40]wt% and [0, 5, 15, 20, 35, 50]wt% respectively. Results demonstrated that while increasing the concentration of either plasticizer independently improved the ionic conductivity, increasing their concentrations simultaneously appears to have a synergistic effect. 40wt% SCN, 35wt% [BMPyrr][TFSI] achieved the highest conductivity of 2.89 x10-3 S/cm. To gain a better understanding of this superior ionic conductivity behavior, morphological and chemical compositions of these samples were characterized using Xfraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS). To examine electrochemical performance, the highest conductivity electrolytes were assembled into half cells with an LFP cathode and lithium metal anode. The resultant cells demonstrated high specific capacity, rate capability, and good columbic efficiency.
