Contiguous High-Mobility Interphase Surrounding Nano-Precipitates in Polymer Matrix Solid Electrolyte

Abstract

We establish that an interfacial region develops around amorphous Li1.3Al0.3Ti1.7(PO4)3 (LATP) nanoparticles in a poly(ethylene oxide) (PEO), which exhibits a 30 times higher Li+ mobility than the polymer matrix. To take advantage of this gain throughout the material, nanoparticles must be uniformly dispersed across the matrix, so that the interphase formation is minimally blocked by LATP particle agglomeration. This is achieved using a water-based in situ precipitation method, carefully controlling the temperature schedule during processing. A maximum conductivity of 3.80 × 10–4 S cm–1 at 20 °C for an ethylene oxide to Li ratio of 10 is observed at 25 wt % (12.5 vol %) particle loading, as predicted by our tri-phase model. Comparative infrared spectroscopy reveals softening and broadening of the C–O–C stretching modes, reflecting increased disorder in the polymer backbone that is consistent with opening passageways for cation migration. A transition state theory-based approach for analyzing the temperature dependence of the ionic conductivity reveals that thermally activated processes within the interphase benefit more from higher activation entropy than from the decrease in activation enthalpy. The lithium infusion from LATP particles is small, and the charge carriers tend to concentrate in a space-charge configuration near the particle/polymer interface.

Softening of PEO–LiTFSI/LLZTO Composite Polymer Electrolytes for Solid-State Batteries under Cyclic Compression

“…Uniform particle dispersion without agglomeration is important for maximizing the efficiency of interfacial regions between ion-conducting particles and their surrounding polymer matrix . Clustering of particles is also known to affect the overall Young’s modulus for nanoreinforced polymer composites .…”

“…Uniform particle dispersion without agglomeration is important for maximizing the efficiency of interfacial regions between ion-conducting particles and their surrounding polymer matrix. 29 Clustering of particles is also known to affect the overall Young’s modulus for nanoreinforced polymer composites. 30 In order to examine particle distribution, transmission X-ray microscopy (TXM) was performed for both particle sizes (500 nm and 5 μm), examining the as-fabricated specimens as well as those that were subjected to cyclic compression.…”