Density functional theory calculations for the interaction of Li+ cations and PF6- anions with nonaqueous electrolytes

The interaction of lithium (Li+) cation and hexafluorophosphate (PF6-) anion with nonaqueous electrolytes is studied by using density functional theory at the B3LYP/6-311++G(d,p) level in the gas phase in terms of the coordination of Li+ and PF6- with these solvents. Ethylene carbonate (EC) coordinates with Li+ and PF6- most strongly and reaches the anode and cathode most easily because of its highest dielectric constant among all the solvent molecules, resulting in its preferential reduction on the anode and oxidation on the cathode. For cyclic carbonates EC and propylene carbonate (PC), the structure Li+(S)(4) is found to be the most stable. However, for linear carbonates dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), the formation of PF6-(S)(n=1-3) is not favorable. Such analysis may be useful in applications for lithium ion batteries.