To explain the dependence of conductivity on particle volume fraction, we note that with increasing φ, the cation presence in the bulk solvent sites decreases (Figure ) due to the increasing number of surface sites. As a consequence, the D cat values exhibit a monotonic decrease with nanoparticle loading. Further, due to the weaker electrostatic interactions between the larger cations and solvent molecules (SI, Section S5.7), the local cation diffusivity in the bulk region is seen to increase with increasing cation size (Figure ). This explains the corresponding monotonic increase in conductivity with cation size.