The utilization of solid lithium metal in lithium ion batteries increases performance and capacities but introduces safety issues when combined with liquid electrolytes. This prevents its use in practical energy dense electrochemical cells, like those required for electric vehicles or consumer electronics. Safety can be increased by using polymer or gel electrolytes which are less flammable and provide a more formidable barrier to dendrite formation. However, the production of polymer electrolytes can often be complicated and involve several stages, making the processing time-consuming and expensive to apply on the industrial scale.

In this work we developed a simple bulk polymerization method in the presence of lithium salt to produce quick-curing vinyl ether based polymer electrolytes in a one-step cationic UV photopolymerization. These electrolytes are composed of ethyl vinyl ether (EVE) monomer and poly(ethylene glycol) divinyl ether (DVEp) crosslinker with triarylsulfonium hexafluorophosphate salt photoinitiator and bis(trifluoromethane) sulfonimide (LiTFSI) lithium salt. Systems with varying crosslinker to monomer (DVEp:EVE) volume ratios and lithium salt concentration ratios were produced to see the effects of crosslinking density and [O]:[Li] ratio on electrolyte properties. Attenuated Total Reflectance Fourier-transform Infrared spectroscopy (ATR-FTIR) was used to quantify polymer composition and verify complete polymerization. Ionic conductivities were measured from 0 to 80 °C using electrochemical impedance spectroscopy. The highest ionic conductivities were seen in samples with the lowest crosslinker concentrations and the highest lithium salt concentrations. The most conductive sample produced had composition 10:1 [O]:[Li] and 15% crosslinker by volume and reached an ionic conductivity of 1.2x10^-6 S/cm at 20°C. Glass transition temperatures (T_g) were measured with differential scanning calorimetry (DSC) for various salt-free DVEp:EVE ratios; T_g was determined to be -15°C for composition with 15% crosslinker in the absence of salt. Investigation of the effect of salt on T_g’s and the electrochemical stability of these compositions is currently underway and will be reported.