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Abstract We performed DFT calculations to investigate the role of solvent of the non-aqueous electrolytes for the oxygen reduction reaction (ORR) kinetics in Li-air batteries. The calculated results on structural, thermodynamic and vibrational properties revealed that dimethyl sulfoxide (DMSO) is the most stable solvent among DME, DMSO, and MeCN of non-aqueous electrolytes. The LiCF 3 SO 3 /DMSO electrolyte was primarily assumed to be the most favorable for ORR kinetics from the IR analysis. We calculated thermodynamic properties of the ORR reactions held during the formation of superoxide (O 2 −) ion and the sole discharge products lithium peroxide (Li 2 O 2), and lithium oxide (Li 2 O) to study the ORR kinetics of the stable salt LiCF 3 SO 3 with three solvents namely dimethoxyethane (DME), dimethyl sulfoxide (DMSO), and acetonitrile (MeCN). The thermodynamic properties of the ORR reaction signified the best role of LiCF 3 SO 3 /DMSO electrolyte compared to LiCF 3 SO 3 /DME and LiCF 3 SO 3 /MeCN both in the gas and solution (water) phases. Highlights • The role of solvent of non-aqueous electrolyte in Li-air batteries was studied theoretically. • The LiCF 3 SO 3 /DMSO electrolyte was primarily assumed to be the most favorable for ORR kinetics from the IR analysis. • The thermodynamic properties of the ORR reactions including the (O 2 −) ion and Li 2 O 2 and Li 2 O • Improved ORR kinetics was due to the key role of LiCF 3 SO 3 /DMSO electrolyte compared to LiCF 3 SO 3 /DME and LiCF 3 SO 3 /MeCN. [ABSTRACT FROM AUTHOR]

We systematically investigated the tuning of the reduction potentials ( E 0 ) for the first row transition metal (M = Cr, Mn, Fe, Co, Ni) complexes with the functionalized 1,4,7-Triazacyclononane-N,N',N”-triacetate (TCTA) ligands by means of DFT calculations. To predict reliable E 0 , the modified UB3LYP functional and equilibrium concept between high and low spin states were utilized. The functional groups NH 2 , CN, −F, and NO 2 were attached to the carbon atoms carefully selected by considering the LUMO and steric hindrance. Based on firmed accuracy of DFT calculations, finally we obtained the calculated E 0 for a series of complexes. It was found that electron donating group such as NH 2 will cause a negative shift of E 0 while electron withdrawing groups have the opposite effect. The overall trend of the calculated E 0 s according to ligand modifications were predicted to have the order as −NH 2 < Pristine < −F ≈ −CN < −NO 2 . In addition, optimized geometries, LUMO, vertical electron attachment and energy components constituting E 0 were discussed in detail to assist the further understanding for E 0 s. Consequently, we suggested that 16 complexes can play a role as an electrolyte in aqueous redox flow battery. They can be classified into 5 groups having similar E 0 ranges: Group I (- 0.6 V ∼ − 0.7 V), Group II (around 0.0 V), Group III (around 0.3 V), Group IV (0.6 ∼ 0.8 V) and Group V (1.1 ∼ 1.2 V). Especially, it is expected that [MnL F ] , [MnL CN ] and [NiL NH2 ] can be used as promising catholyte candidates possibly possessing high E 0 s which almost reach to the reduction potential limitation 1.25 V in aqueous redox flow battery. Our systematic approach to tune E 0 can be applied to the design of other complexes via rational ligand modification. [ABSTRACT FROM AUTHOR]