Optimizing conductivity and cationic transport in crosslinked solid polymer electrolytes

Solid polymer electrolytes (SPEs) are prepared through thiol-ene polymerization with functionalized, potentially bio-based, aromatic monomers. Differing functionality and aromatic content of the monomers vary the glass transition temperatures (T(g)s) and crosslink densities of the resulting polymers, allowing for analysis of the structure-property relationships. Though the SPEs contain repeating PEO segments, the formation of crystalline regions is avoided through the crosslinked nature of the networks. The solid polymer electrolytes exhibit high conductivity values at room temperature, the highest reaching 7.65 x 10(-4) S cm(-1) for the DAVA-containing SPE with 50 mol% LiPF6, and moderate lithium ion transference numbers, the highest reaching 0.39 for the DAGd-containing SPE with 25 mol% LiPF6. Lower polymer T-g is associated with higher overall conductivity, but, the SPEs with higher crosslink densities display higher cationic transport, though the T(g)s are higher. Therefore, it is determined that there exists an optimal range of polymer T(g)s, crosslink densities and neat polymer dielectric constants for high cationic transport through the SPEs; extremes of these parameters are not necessarily beneficial. The promising conductivity and ion transference results, in addition to high initial decomposition temperatures in N-2 ( > 300 degrees C) and great electrochemical stability, reveal potential for these crosslinked, aromatic, thiol-ene polymers in electrolyte applications in lithium-ion batteries.