A quantitative correlation between macromolecular crystallinity and ionic conductivity in polymer-ceramic composite solid electrolytes

Abstract Polymer-ceramic composite electrolytes are considered as an essential component in emerging high-energy-density solid-state batteries. However, the ionic conductivity of such systems is not yet high enough to meet the demands of practical applications. Although ionic conductivity is known to vary qualitatively with different ceramic concentrations and polymer crystallinity, no quantitative correlation between these physical parameters has yet been identified. In this letter, we present a linear correlation between ionic conductivity and polymer crystallinity in such composite electrolytes and propose a crystallinity-conductivity correlation equation through systematically tuning the crystallinity of polymer and measuring the ionic conductivity in a series of poly(ethylene oxide)18-LiClO4-x wt% Li6.4La3Zr1.4Ta0.6O12 and Li10GeP2S12 composites. A parameter Z, obtained from either crystallinity or ionic conductivity using a scaling method, exhibits a linear function with respect to weight loading of the ceramic fillers. These results suggest that macromolecular crystallinity is a quantitative descriptor of ionic conductivity in polymer-ceramic composite electrolytes which can serve as a design rule for improved composite electrolytes.