The superlithiation of organic anodes is a promising approach for developing the next generation of sustainable Li-ion batteries with high capacity. However, the lack of fundamental understanding hinders its faster development. Here, a systematic study of the lithiation processes in a set of dicarboxylate-based materials is carried out within the density functional theory formalism. It is demonstrated that a combined analysis of the Li insertion reaction thermodynamics and the conjugated-moiety charge derivative enables establishing the experimentally observed maximum storage, thus allowing an assessment of the structure-function relationships also.