(506f) Cyclic Carbonate-Based, Single-Ion Conducting Polymer Electrolytes for Li-Ion Batteries

Solid polymer electrolytes (SPEs) have been proposed to address several issues in Li-ion batteries, including decreased flammability and lithium dendrite growth, and reduced concentration gradients by immobilizing anions to the polymer matrix. Unfortunately, single-ion conducting SPEs continue to suffer from poor lithium-ion conductivity due to the immobilized nature of the anions, poor ion pair dissociation, and the slower time scales of polymer diffusivity compared to liquid electrolytes. Our group investigated cyclic carbonate-based polymer electrolytes to mimic the beneficial properties of commercial carbonate-based liquid electrolytes. A series of copolymers were synthesized varying the structure and composition of the anionic monomer and polar cyclic carbonate containing monomer. The tertiary hydrogen on the cyclic carbonate groups can act as a crosslinking point in free radical curing processes to improve mechanical properties of the SPEs at elevated temperatures. Although the inherent conductivities of the dry single-ion SPEs are on the order of 10^-7 mS/cm, addition of plasticizers can improve these conductivities to 10^-1 mS/cm while maintaining a high transference number, t₊ ≥ 0.90. Judicious choice in plasticizer also leads to formation of stable SEI layers with satisfactory levels of rate and cycling performances.