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

Abstract

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.

Recent progress in electrolyte design for advanced lithium metal batteries

“…The highest occupied molecular orbital (HOMO) of VC is higher than that for EC, respectively, for VC and EC: −10.26 and −12.76 eV. VC is more readily oxidized at the positive electrode surface than EC, preferentially forming a passive layer on the electrode 109,110 . FEC is reported to be a useful additive to boost the formation of CEI because the decomposition of FEC yields an F‐rich passivated layer 111 .…”

“…VC is more readily oxidized at the positive electrode surface than EC, preferentially forming a passive layer on the electrode. 109,110 FEC is reported to be a useful additive to boost the formation of CEI because the decomposition of FEC yields an F-rich passivated layer. 111 These additives improve SEI and promote the formation of CEI because additives containing F, B, and P elements will eventually decompose F-, B-, and P-containing compounds to isolate and prevent direct contact between the electrolyte and the electrode.…”

Study of the Electrochemical Behavior of N-Substituted-4-Piperidones Curcumin Analogs: A Combined Experimental and Theoretical Approach

“…The oxidation potentials at DFT M06 and M06-2x level using 6-311+G(d,p) basis set were obtained for the ten derivatives. M06-2X functionals have been extensively used to calculate redox potentials [ 33 , 34 , 35 , 36 , 37 ]; however, in the specific case of oxidation potential, previous work has shown that functionals with high levels of Hartree–Fock (HF) exchange percentage tend to significantly overestimate the potential [ 38 ]. Therefore, we tested M06-2X (54% HF) and M06 functionals to obtain the potentials.…”

Development of a multi‐step screening procedure for redox active molecules in organic radical polymer anodes and as redox flow anolytes

“…The benchmark values were generated by W. Zhang et al themselves using higher level wave function-based methods. 28 In contrast, this study includes benchmark values from both experiments and higher-level wave function-based methods in parallel. This provides additional information on the deviations between calculations and experiments, and allows for the identification of possible sources of error.…”