Mechanism and modeling of conductivity in polymer electrolytes

The progress of dynamically disordered hopping (DDH) in modelling charge transport in polymer electrolytes is reviewed. The DDH model successfully describes many of the salient features of polymer electrolytes, most notably, the frequency and temperature dependence of the conductivity. Furthermore, analyses and simulations based on the DDH model provide rich mechanistic information. The general picture of charge transport that emerges from the DDH model is one in which two classes of charge carriers exist in thermal equilibrium: quasi-free and bound. The quasi-free carriers dominate the conductivity response and diffuse freely over short distances (≈1 angstrom) with longer range diffusion requiring local segmental motions, renewal in the language of DDH, of the polymer solvent. The bound carriers, which are likely polymer solvated ion clusters, are immobile on the time-scale of renewal and contribute relatively little to the conductivity.