Correcting charge distribution in reduced Li-molecule pair for computational screening of battery solvents

Li-molecule pair is a widely used model for the simulation of reduction in Li-ion batteries. We demonstrate that this model provides incorrect results for some solvents. When an electron is added to the Li-molecule pair, it may go to the lithium-ion and neutralize it. Instead, we suggest placing this additional electron on the molecule using constrained density functional theory (CDFT). This approach resembles electron behaviour in the condensed phase and reproduces the physics of the reduction. We demonstrate that suggested in this work approach provides improved agreement with experimental data. Suggested CDFT-based method is fast, reliable and may be used in computational screening of solvents. We demonstrate the practical application of the method by benchmarking it on a set of 30 molecules from the electrolyte solvent database.