We present an extensive study of ionic transport in PolyG(30)LiPF(6), which is a crosslinked poly(ethylene oxide)-poly(propylene oxide(PEO-PPO) random copolymer complexed with LiPF(6) to an oxygen-to-cation ratio of 30 : 1. Self-diffusion coefficients of the constituent ions were measured by pulsed field gradient nuclear magnetic resonance (PFG-NMR) as a function of temperature using the signals of (7)Li and (19)F. These data were compared with the charge diffusivity as derived with the Nernst-Einstein equation from the ion conductivity obtained by impedance spectroscopy. In addition, the diffusion behaviour of a foreign cation (sodium) and that of a foreign anion (iodine) in PolyG(30)LiPF(6) were investigated by means of the radiotracers (22)Na and (125)I. All different types of diffusivities were evaluated in a comprehensive ion transport model which allows for the occurrence of charged single ions and neutral ion pairs. Simultaneous fitting of all data within this model yields best values of the model parameters which include Vogel-Tammann-Fulcher parameters and enthalpies/entropies of pair formation. Two distinct variants of the same general model reproduce the experimental data equally well, i.e., with closely similar results for the pair contribution to the migration of each ionic species. In the first variant, this pair contribution is due to a small fraction of ion pairs with a high mobility. By contrast, the second variant results in a very large fraction of pairs characterized by a relatively low mobility. The assumptions and implications connected with both model variants are discussed in detail.

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.