Theoretical analysis on de-solvation of lithium, sodium, and magnesium cations to organic electrolyte solvents

De-solvation of a Li ion at an electrode/electrolyte interface can be the rate-determining step of the reaction in lithium-ion secondary batteries. The present study theoretically evaluates the de-solvation energies of Li, Na, and Mg ions to organic electrolyte solvents. The Na-ion complexes revealed commonly smaller de-solvation energies compared to the Li-ion complexes due to the weaker Lewis acidity, while the solvation structures were similar to each other. The Mg-ion complexes showed remarkably larger de-solvation energies because of the double positive charge. The increase of coordination number, which was associated with the change in the solvation structure, was observed for the Mg-ion complexes. Detailed analysis revealed good correlations between the de-solvation energies and the electrostatic potentials made by the solvents, as well as the chemical hardness of the solvents.