Effect of interfacial structures on ionic conductivity in particle-dispersed composite electrolytes

Enhancement of ionic conduction in NaCl-Al2O3 and NaCl-TiO2 composites has been investigated by non-equilibrium molecular dynamics (NEMD) simulations. For quantitative discussion of ionic diffusion in NaCl matrices, activation energy of sodium vacancy VNa in an imperfect NaCl crystal was initially evaluated from results of NEMD simulations under some electric fields. The activation energy agrees well with experimental data. Simulations with NaCl(100)-Al2O3(110) and NaCl(100)-TiO2(001) hetero-interfaces have been performed for clarifying vacancy motion near interfaces. Structural disorder appeared around the hetero-interface. The simulation cells were constituted of ordered and disordered structure even if in equilibrium state without applying an electric field. The vacancies near the hetero-interface show large diffusion constants on the ionic conductivity in the present NEMD simulations. It seems that the vacancy motion near the interface contributes to the enhancement of the conduction in the composites.