Identifying Descriptors for Solvent Stability in Nonaqueous Li-O2 Batteries.

One crucial challenge in developing rechargeable Li-O2 batteries is to identify a stable solvent that is resistant to decomposition in the electrochemical environment of Li2O2. We attempt to identify descriptors that could be used to test for solvent stability. We build on the recent quantitative experimental results on oxygen consumption and release during discharge and charge respectively. We limit our focus to understanding trends in oxidative stability of solvents and based on a systematic treatment of the electrochemical environment of Li2O2, we propose that, to a first approximation, the highest occupied molecular orbital (HOMO) level could be a good descriptor. We demonstrate that this descriptor correlates well with the experimentally measured degree of rechargeability. We utilize this descriptor to screen a large number of solvents and identify several solvents that could enhance the rechargeability of nonaqueous Li-O2 batteries. We provide a comprehensive compilation of available computational and experimental data of several key solvent parameters that we believe will be the genesis for an 'electrolyte genome'.