Accurate redox potentials for solvents in Li-metal batteries and assessment of density functionals

The practical applications of Li metal batteries (LMBs) have been limited by the anodic instability which causes fatal problems including low Coulombic efficiency and short cycling lifespan. One way of addressing this issue is to develop new solvents with suitable redox potentials for electrolytes of LMBs. By using the recently developed Wuhan-Minnesota-scaling method, the work has developed the Redox20 benchmark database consisting of the Ox10 subset of 10 oxidation potentials and the Red10 subset of 10 reduction potentials for four conventional and six fluorinated solvents in LMBs. The performances of 35 DFT methods have been assessed against Redox20. Based on the assessments, M05-2X, M08-HX, M08-SO, M06-2X, and revM06 functionals are the most accurate for the predictions of oxidation potentials, and the N12, M06-HF, M08-HX, HSE06, and PW6B95-D3 functionals are best performers for calculating reduction potentials. M08-HX gives the lowest average mean unsigned error, and it is recommended for the calculation of redox potentials. M08-HX has been employed to calculate the redox potentials and highest occupied molecular orbital/lowest unoccupied molecular orbital structures of 48 solvents for LMBs, which is beneficial to the selection of optimal LMBs electrolyte solvents.