Dispersive ionic space charge relaxation in solid polymer electrolytes. II. Model and simulation

Abstract

Dynamic Monte-Carlo simulations of ionic space charge relaxations are carried out using a three-dimensional model for thermally activated ion hopping in a multiwell energy structure. In this model a solid polymer electrolyte is embedded between two ideal blocking electrodes. The polymer is subdivided into 100ϫ100ϫ100 lattice cells. Positive ions ͑typically 1000͒ are distributed on the cells. To provide charge neutrality a negative background charge, constant in space and time, is introduced. The positive ions are able to hop between neighboring cells, surmounting energy barriers of distributed heights. The barrier heights consist of an intrinsic part due to the polymer structure, a part due to the Coulomb interaction of the ions, and a part due to the externally applied field. To calculate the interaction between the ions and the electrodes a method of images is used. Periodical boundary conditions are used for those lattice surfaces which are not in contact with the electrodes. The ionic space charge polarization process is simulated as dependent on the time, the sample thickness, the ion concentration, and the externally applied voltage. The polarization current after a step of the electric field shows dispersion due to distributed energy barrier heights in the short time range and a Kohlrausch behavior due to image charges in the long time range.

Electrical transport study of potato starch-based electrolyte system

“…Theoretical prediction claims [34] that value of n for small time scale should be small (∼0.25) and that for the higher scale should be high ∼1.1. Surprisingly in present study, n is approximately of the same order but for opposite time scales.…”

“…Salt containing materials have t ion >0.97. Polarisation processes in ionic conductors are known to show dispersion in the response function over time scale [34]. After the application of step electric field, the behaviour can be explained by power law where current follows t −n having 0<n<2.…”

Space charges in solid electrolytes detected by the scanning Kelvin probe

“…6(b)). In the thinner samples the space charge region is build up faster as shown by Wagner and Kliem [21]. This region is mainly responsible for the initiation of the charge injection.…”

“…A detailed description of the model is given in Refs. [19][20][21]. Here, negative mobile ions fluctuate in a multi-well energy structure thermally activated over energy barriers of the height W eff .…”

Monte Carlo simulation of ion transport of the high strain ionomer with conducting powder electrodes

“…Wagner and Kliem [19] have developed a three dimensional discrete ion hopping model for polyethylene oxide (PEO). They studied steady state charge distribution and dynamic properties such as polarization, current density, system relaxation.…”