Here, k B T is the thermal energy and r α i (t) is the position vector of particle α relative to the center-of-mass position of the entire electrolyte (excluding the carbon atoms). As we only consider transport in the xy-plane (parallel to the graphene sheets), r α i (t) is a two-component vector, and we include a factor of 1/4 in the prefactor of Eq. (3) rather than the factor of 1/6 used in isotropic systems. The angular brackets denote averaging over time origins within the trajectory, and the indices i and j denote the species type (cation or anion). As mentioned above, we define the volume V of the electrolyte as V = L x L y (H -2r C ), where r C is the van der Waals radius of carbon, 1.7 Å, H is the separation distance between the graphene layers, and L x and L y are the dimensions of the graphene sheet in the x-and y-directions, respectively. The same definition of volume is used when computing the density in Fig. .