Lithium Ion Conducting Poly(ethylene oxide)-Based Solid Electrolytes Containing Active or Passive Ceramic Nanoparticles

Polymer-based solid electrolytes containing ceramic nanoparticles are attractive alternatives to liquid electrolytes for high-energy density Li batteries. In this study, three different types of fillers have been dispersed in poly(ethylene) oxide (PEO) polymer matrices, and the effects on the resulting ionic conductivity of the nanocomposites have been examined. In this respect, the efficacy of one active, liquid-feed flame spray pyrolysis synthesized amorphous Li1.3Al0.3Ti1.7(PO4)3 (LATP), and two passive filler materials, TiO2 and fumed silica nanoparticles, are compared. Nanocomposite electrolytes are prepared with up to 20 wt % particle loadings. PEO/LiClO4 with 10 wt % LATP nanoparticles exhibits an ionic conductivity of 1.70 × 10–4 S·cm–1 at 20 °C, the highest among the surveyed systems, despite exhibiting comparable or higher degrees of crystallinity and glass transition temperatures than the systems containing passive fillers. The ionic conductivity of the composites with LATP nanoparticles exceed that of the polymer matrix by 1 to 2 orders of magnitude. We attribute this remarkable enhancement to cation transport within the interphase region surrounding the particles, which achieves percolation at low nanoparticle loading. The development of this interphase structure is influenced by the active nature of the LATP filler, and we estimate the inherent conductivity of the interphase to be 3 to 4 times higher than the maximum measured value.