  Solid polymer electrolytes exhibit ion conduction and high mechanical
properties, thus are promising materials for future energy storage devices. The
ion conductivity in an SPE is intricately connected to salt ion distribution in
the polymer matrix. The relationship between ion diffusion and ion distribution
remains unresolved. Here, we conduct coarse grained molecular dynamics
simulations and establish correlations between ion distribution and transport
for a phenomenological SPE model. We propose phase diagrams of SPEs as a
function of ion pair size, ion concentration and the Bjerrum length of the
material. A crossover from a discrete ion aggregate to a percolated ion
aggregate is demonstrated as a function of ion pair size in the SPE. Further,
we determine ion diffusions for all the phases of the SPE. The work provides
important design strategies for controlling ion distribution and enhancing ion
conductivity in a polymer matrix.
