In Table , we list the calculated lattice parameters for C 6 , LiC 12 , and LiC 6 from PBE D3, PBE D3-BJ, and rVV10. For each compound, the calculated a lattice parameters with different DFT methods are similar with a difference less than 0.02 and they agree well with experimentally reported values. The c lattice parameters, on the other hand, vary significantly, which indicates the importance of correcting the vdW forces between the graphene layers. Overall, we found that the best match with experimental lattice parameters is obtained with the rVV10 functional. Next, we investigated the effect of DFT methods on thermodynamic stability of the Li x C 6 compounds at different Li concentrations and stages. Here we considered four stages of Li x C 6 with n=1, 2, 3, and 4. Figure illustrates the calculated formation energies of 18 Li x C 6 compounds from PBE D3, PBE D3-BJ, and rVV10. It can be seen that the formation energies of all intermediate Li x C 6 compounds are above zero with PBE D3 and PBE D3-BJ, which indicates that the PBE functional tends to underestimate the thermodynamic stability of the Li x C 6 compounds. On the other hand, the non-local rVV10 functional (see Figure ) predicts several stable intermediate Li x C 6 compounds which lie on the convex hull, such as stage 2 LiC 12 and stage 3 LiC 24 . An earlier study reported that the stability underestimation from PBE D3 and PBE D3-BJ is mainly because the PBE functional overbinds the carbon atoms in C 6 . Using the PBE functional, Persson el al. had to add an empirical vdW binding energy for every empty graphite layer in stage 2 to properly study the thermodynamic and kinetic properties of the Li x C 6 system. Based on lattice parameters and thermodynamic stability results we selected the rVV10 functional for all following DFT calculations and constructing the training dataset.