Voltage- and incremental charge capacity-composition curves for the electrochemical formation of intercalates Li xMoS2 were analyzed at the molecular level by developing a quantum chemical model focused on the variation of the electron chemical potential. Experimentally observed trends of the charge capacity in the range 0<x<0.6 are successfully described by the global hardness index as defined within the density functional theory. Contrasting with classical descriptions like the gas lattice model assuming complete lithium-MoS2 one electron transfer, proposed model leads, agreeing with previous experimental evidence, to a system in which electron density is partially retained in the lithium atom. The model permits moreover to identify a sequence of octahedral and tetrahedral sites as the more favorable migration pathway for the diffusion of lithium through the interlaminar space