Abstract
Hybrid solid electrolytes are composed of organic (polymer) and inorganic (ceramic) ion conducting materials and are promising options for large-scale production of solid state lithium metal batteries. Combining an inorganic conductor with a polymer electrolyte improves the mechanical properties and limits dendrite growth in metal batteries (i.e. short circuiting). However, hybrid electrolytes are comprised of numerous interfaces. There are intrinsic interfaces that form between material junctions in the solid electrolyte between the inorganic and organic ion conducting materials. Depending on the loading of the inorganic material, the electrolyte can experience different mechanical and electrochemical properties. There are two percolation thresholds that exist in hybrid electrolytes: (1) long-range connectivity of inorganic particles (contact mode) and (2) long-range connectivity of space charge layers. The former is achieved at high loadings of 33 vol% (ceramic:polymer) and the later is achieved at ~4 vol% (ceramic:polymer). There is currently a critical lack in understanding regarding transport in these inorganic/organic electrolyte systems, but there is clear evidence that it is reliant on the underlying structure of the inorganic particles. At minimal loading, the superior ion conduction is generally attributed to the rapid interphase conduction. Although this addition of active/passive ceramic nanofillers within polymer matrix showed better ionic conductivity, this is often hindered by unwanted particle agglomeration at higher loadings. Nano-CT allows us to look in to the structural heterogeneity of PEO-LLZO composite systems which is beneficial in understanding the continuous percolated network for ion conduction (Fig. 1). This presentation intends to use a multi-modal approach which couples physics-based modeling with electrochemical, and synchrotron x-ray nanotomography experiments to probe the origin of low ionic conductivity in these hybrid electrolyte systems.
Figure 1