Rubidium impurity diffusion in a poly(ethylene oxide)-sodium iodide polymer electrolyte.

Diffusion of the radioisotope (86)Rb in an amorphous polymer-salt complex consisting of poly(ethylene oxide) and sodium iodide was found to be faster at all temperatures investigated than tracer self-diffusion of the smaller alkali metal cation (22)Na. This is the striking result of the first study on impurity diffusion in a polymer electrolyte system and a comparison with ionic self-diffusion and conductivity data previously obtained from the same system. The experimental findings can be rationalized within an ion transport model based on the occurrence of charged single ions and neutral ion pairs.