Theoretic Calculation for Understanding the Oxidation Process of 1,4-Dimethoxybenzene-Based Compounds as Redox Shuttles for Overcharge Protection of Lithium Ion Batteries

The effect of substituents on the oxidation potential for the one-electron reaction of 1,4-dimethoxybenzene was understood with a theoretical calculation based on density functional theory (DFT) at the level of B3LYP/6-311+G(d). It is found that the oxidation potential for the one-electron reaction of 1,4-dimethoxybenzene is 4.13 V (vs Li/Li+) and can be changed from 3.8 to 5.9 V (vs Li/Li+) by substituting electron-donating or electron-withdrawing groups for the hydrogen atoms on the aromatic ring. These potentials are in the range of the limited potentials for the lithium ion batteries using different cathode materials, and thus the substituted compounds can be selected as the redox shuttles for the overcharge prevention of these batteries. The oxidation potential of 1,4-dimethoxybenzene decreases when the hydrogen atoms are replaced with electron-donating groups but increases when replaced with electron-withdrawing groups. The further oxidation of these substituted compounds was also analyzed on the basis of the theoretic calculation.