Effect of Interfacial Space‐Charge Polarization on the Ionic Conductivity of Composite Electrolytes

An enhanced carrier concentration within the interfacial space‐charge layers has been proposed as one possible mechanism leading to the enhanced ionic conductivity observed for a variety of composite electrolytes containing a dispersed second phase of fine insulating particles such as A1 2 O 3 . This study tests this proposal by estimating the maximum space‐charge polarization that might reasonably occur at interfaces of nominally pure AgCI, β‐AgI, and LiI. The resulting interface conductances are used in effective medium calculations of the total conductivity of a randomly distributed composite of these salts with A1 2 O 3 particles. Comparison of the results with published conductivities for the composites shows that the modest enhancement found for AgC1/A1 2 O 3 can be accounted for by the interfacial space‐charge polarization. However, the large (50‐ to 500‐fold) enhancements found for β‐AgI/A1 2 O 3 and LiI/A1 2 O 3 must be attributed to another mechanism.