Dispersion-corrected DFT calculations were performed to investigate energetically stable structures of a Li+ cation solvated by some PC molecules inside an AB-stacked graphene bilayer (2G) with a variant interlayer spacing (L ranging from 5 to 8 Å), denoted by PC n –Li+@2G­(L), where n is the number of PC molecules (1 ≤ n ≤ 3). The 2G­(L) structures model slit-type pore geometries of microporous carbons, where the interlayer spacing corresponds to their pore width. DFT calculations found L- and n-dependences of stabilized PC n –Li+@2G­(L) structures due to different degrees of CH−π and cation−π interactions between a graphene bilayer host and a PC n –Li+ guest. Since the interlayer space of 2G­(L) at L = 6 Å is the smallest limit that can accommodate a single PC molecule, the restricted interlayer space can be utilized to selectively stabilize a PC1–Li+ structure due to attractive cation−π interactions and negligible CH−π interactions. Within a larger interlayer space of graphene bilayers (L ≥ 7 Å), attractive cation−π and CH−π interactions between the host and guests are significant for stabilizing inner PC n –Li+ structures (n ≥ 3). Similar structural preferences can be found in the solvated state of Na+ cations within the interlayer space of 2G­(L) at L = 6 Å. By using the distance of a Li+ cation from a carbon layer in the PC n –Li+@2G­(L) structures compared with that in the optimized PC4–Li+ structure on a graphene monolayer (1G) as a model of external and macroporous carbons, the capacitances of PC n –Li+@2G­(L) structures relative to that of PC4–Li+ structure on 1G were approximately estimated. The estimated capacitance of the PC1–Li+ structure stabilized inside 2G­(L) at L = 6 Å is almost twice as large as that in PC4–Li+ on the 1G structure. Accordingly, the DFT calculations revealed that the confinement of PC n –Li+ structures within microporous carbons whose pore size is around 6 Å significantly enhances the capacitance relative to those in external or macroporous carbons due to the selective formation of the significantly desolated Li+ cations.