Computational Study of Li⁺ Transport in Mixed Solid Polymer Electrolytes Containing Microscopic Interfaces

For practical application, solid polymer electrolytes (SPE) are often required to achieve high conductivity, high transference number, and high mechanical strength simultaneously. Many SPE designs therefore mix different chemical species to introduce the added functionalities beyond Li⁺ conduction. Varying degrees of mixing of the added components into conducting components tends to alter the dynamics of the polymer host and the solvation environment for Li⁺. This poster features computational studies that attempt to understand and quantify the effect of mixing. One study considers Li⁺ transport in mixtures of the poly (ethylene oxide) (PEO) and poly (methyl methacrylate) (PMMA) couple, where effects of miscibility on Li⁺ transport can be examined in isolation. A graph-based transport model is proposed to effectively quantify long-range transport of Li⁺ in the mixtures. The second study considers mixed graft copolymer electrolytes containing a polarity contrast, using poly(glycerol carbonate methacrylate) (PGCMA) and poly (oligoethylene methacrylate) (POEM) as building blocks. Simulations reveal how entropy governs the solvation site formation and Li⁺ transport in those mixed-polarity SPEs containing microscopic interfaces of varying sharpness. The study also concludes that the synergy of polarity and mobility contrast for conductivity observed in liquid electrolytes is not transferable to polymeric systems, due to fundamentally different Li⁺ solvation and transport mechanisms.