We applied static and dynamic hybrid functional density functional theory (DFT) calculations to study the interactions of one and two excess electrons with ethylene carbonate (EC) liquid and clusters. Optimal structures of (EC)(n) and (EC)(n)(-) clusters devoid of Li+ ions, n = 1-6, were obtained. The excess electron was found to be localized on a single EC in all cases, and the EC dimeric radical anion exhibits a reduced barrier associated with the breaking of the ethylene carbon-oxygen covalent bond compared to EC-. In ab initio molecular dynamics (AIMD) simulations of EC- solvated in liquid EC, large fluctuations in the carbonyl carbon-oxygen bond lengths were observed. AIMD simulations of a two-electron attack on EC in EC liquid and on Li metal surfaces yielded products similar to those predicted using nonhybrid DFT functionals, except that CO release did not occur for all attempted initial configurations in the liquid state. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3545977]