The electronic states of aqueous species can mix with the extended states of the solvent if they are close in energy to the band edges of water. Using density functional theory-based molecular dynamics simulation, we show that this is the case for OH(-) and Cl(-). The effect is, however, badly exaggerated by the generalized gradient approximation leading to systematic underestimation of redox potentials and spurious nonlinearity in the solvent reorganization. Drawing a parallel to charged defects in wide gap solid oxides, we conclude that misalignment of the valence band of water is the main source of error turning the redox levels of OH(-) and Cl(-) in resonant impurity states. On the other hand, the accuracy of energies of levels corresponding to strongly negative redox potentials is acceptable. We therefore predict that mixing of the vertical attachment level of CO2 and the unoccupied states of water is a real effect.

Solvent degradation due to reactivity with various oxygen species is one of the most important issues in aprotic Li-O 2 batteries. Recently, a more complete mechanism for discharge in an aprotic Li-air battery has been proposed, which accounts for the formation of solvated peroxides by disproportionation. In the present work, nucleophilic attacks by one of these solvated peroxides, LiO 2 − (solv) on some commonly used solvents in aprotic Li-air batteries, including acetonitrile (MeCN), 1-methyl-2-pyrrolidone (NMP), dimethoxy ethane (DME), and dimethyl sulfoxide (DMSO) have been explored by calculating the reaction and activation free energies using density functional theory (DFT) Active research 1-17 on the aprotic Li-air battery has been drawn by its high theoretical energy and power storage capacities of 11,000 Wh/kg and 3800 mAh/g, respectively.18,19 These values double those of the most advanced lithium ion batteries and close to those of gasoline. However, many challenges 20 must be overcome before a commercially viable battery can be produced. One critical issue is the degradation of solvents during the charge and discharge cycles of the battery. Common solvents in Li-air batteries such as propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC) have long been shown to degrade during discharge and fail to produce lithium peroxide (Li 2 O 2 ), the desired discharge product in a twoelectron process 21-23 described byBryantsev et al. [24][25][26] attributed this failure to the reactions between these solvents and the superoxide radical ion (O 2 − ) with the latter formed inevitably during discharge in the one-electron reduction of oxygen shown in Equation 2 as