The Use of Radiotracer Diffusion to Investigate Ionic Transport in Polymer Electrolytes: Examples, Effects, and Their Evaluation

The paper highlights some remarkable results obtained by applying the radiotracer diffusion (RTD) technique to the study of ionic transport in salt-in-polymer electrolytes. The technique is based on the determination of a radiotracer depth profile by serial sectioning following isothermal diffusion annealing. Unlike alternative methods, RTD is able to measure the self-cation and self-anion diffusivity even for systems dilute in salt. Another unique feature is the capability to investigate foreign-ion diffusion at extremely low concentration levels. Combined with DC conductivity data, RTD may provide a virtually complete picture of mass and charge transport in solid-like polymer electrolytes (SPEs). The paper describes the special SPE-related procedures used in the RTD experiments and their analysis. The advantages of the method will be demonstrated with selected examples of self- and foreign-ion diffusion in prototype SPE systems. We also present prominent examples of RTD dealing with the effects of salt precipitation and oxide nano-particles used as dispersed filler material.