We study the effect of ion concentration on the ionic conductivity of the model system by preparing a series of LiOTf and LiTFSi coordinated PDMS with different salt concentrations (LiOTf0.2 to LiOTf1.4 and LiTFSi0.2 to LiTFSi1.4, the number in the sample name indicates the mole ratio of PDMS:LiOTf= 1 : n for formulations that deviate from 1 : 1). In both cases, the ionic conductivity of the PDMS complex first increases and then decreases as the Li salt concentration increases; the highest ionic conductivity is reached at around the maximum coordination capacity of the ligands with Li + cations (corresponding to PDMS:Li salt= 1 : 1 in Figure , Table ). This indicates that at first, more Li + cations and counter anions exist in the system as the Li salt concentration is increased, improving the ionic conductivity. However, when the ligand coordination capacity is oversaturated by excess Li salt, the ionic conductivity of the PDMS complex starts to decrease monotonically (Figure ). As both seen from the previous studies and our MD simulation (Figure ), ion pairs and higher-order clusters form at high Li salt concentration, which hinders the effective cation-anion dissociation and ion transport, thereby decreasing the overall ionic conductivity. We can look more deeply into the mechanism for the salt concentration dependence with PFG SE NMR and MD simulations. It can been clearly seen from the trend of PDMS-L, LiOTf0.4, and LiOTf, that the segmental motion of PDMS chain slows down when forming complexes with LiOTf, and decreases further at higher LiOTf concentration (Figure ), because the formation of metal-ligand coordination adds temporary constraints to the chain ends. The diffusion of OTf -also slows down at higher LiOTf concentration, confirming that the anion motion is associated with the chain motion. The MD calculated diffusion of the anions follows the same trends as the NMR results. The MSD plots from MD simulations (Figure ) also show that the mobility of both the ions and the chain decrease with higher salt concentration. Therefore, when the PDMS is oversaturated by Li salt, both clustering and reduced segmental motion can inhibit the overall ionic conductivity of the material. In this particular material system, chain mobility seems to be a secondary effect since the peak conductivity occurs near a molar ratio of 1:1, which clearly has reduced chain mobility.