title: Density functional theory study of the role of anions on the oxidative decomposition reaction of propylene carbonate.
abstract: The oxidative decomposition mechanism of the lithium battery electrolyte solvent propylene carbonate (PC) with and without PF(6)(-) and ClO(4)(-) anions has been investigated using the density functional theory at the B3LYP/6-311++G(d) level. Calculations were performed in the gas phase (dielectric constant ε = 1) and employing the polarized continuum model with a dielectric constant ε = 20.5 to implicitly account for solvent effects. It has been found that the presence of PF(6)(-) and ClO(4)(-) anions significantly reduces PC oxidation stability, stabilizes the PC-anion oxidation decomposition products, and changes the order of the oxidation decomposition paths. The primary oxidative decomposition products of PC-PF(6)(-) and PC-ClO(4)(-) were CO(2) and acetone radical. Formation of HF and PF(5) was observed upon the initial step of PC-PF(6)(-) oxidation while HClO(4) formed during initial oxidation of PC-ClO(4)(-). The products from the less likely reaction paths included propanal, a polymer with fluorine and fluoro-alkanols for PC-PF(6)(-) decomposition, while acetic acid, carboxylic acid anhydrides, and Cl(-) were found among the decomposition products of PC-ClO(4)(-). The decomposition pathways with the lowest barrier for the oxidized PC-PF(6)(-) and PC-ClO(4)(-) complexes did not result in the incorporation of the fluorine from PF(6)(-) or ClO(4)(-) into the most probable reaction products despite anions and HF being involved in the decomposition mechanism; however, the pathway with the second lowest barrier for the PC-PF(6)(-) oxidative ring-opening resulted in a formation of fluoro-organic compounds, suggesting that these toxic compounds could form at elevated temperatures under oxidizing conditions.
authors: Department of Materials Science and Engineering, University of Utah, Salk Lake City, Utah 84112, USA.
authors: Lidan
authors: L
authors: Xing
authors: Oleg
authors: O
authors: Borodin
authors: Grant D
authors: GD
authors: Smith
authors: Weishan
authors: W
authors: Li
mesh_terms: D000838:Anions / Q000737:chemistry; D010084:Oxidation-Reduction; D011407:Propane / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D000838:Anions; C045990:propylene carbonate; D011407:Propane