Calculations are made of the ionization potential (IP) and the oxidation potential (E ox) values of 108 organic molecules that are potential electrolyte additives for the overcharge protection of lithium-ion batteries (LIBs). The calculated E ox values are in close agreement with the experimental ones, where the root-mean-square deviation is 0.08V and the maximum deviation is 0.15V. The molecules exhibiting high E ox (>4.5V) show one of the following two features: (1) IP>7.70eV or (2) IP<7.70eV with a relatively large molecule size. Consideration of bulk solvent effects, in particular the electrostatic attraction between solute and solvent, is crucial in determining E ox. Considering its accuracy and reliability, the density functional calculation is recommended as a useful tool for screening electrolyte additives for LIBs.