Solvate Structures and Computational/Spectroscopic Characterization of LiCF₃SO₃ Electrolytes

Abstract

An extensive correlation study has been conducted utilizing known LiCF3SO3 solvate crystal structures having specific modes of CF3SO3 –···Li+ ion coordination and the corresponding anion Raman vibrational band positions to delineate the assignments of specific vibrational bands to these ion coordination modes. To facilitate this study, three new crystalline solvate structures(12C4)2:LiCF3SO3, (BN)1:LiCF3SO3, and (MA)1:LiCF3SO3 with 12-crown-4 (12C4), butyronitrile (BN) and methyl acetate (MA)have been determined. The trifluoromethanesulfonate or “triflate” anion is an excellent probe for exploring electrolyte interactions since two separate Raman bands may be used for the evaluation and the anion exhibits a wide range of coordination modes in electrolytes with varying solvents.

Understanding the Influence of Lewis Acids on CO2 Hydrogenation: The Critical Effect Is on Formate Rotation

“…In order to evaluate if the results for 2 are critically dependent on the coordination environment and dissociation state of lithium, we compared models with solvated [Li­(CH 3 CN) 2 ] + or [Li­(CH 3 CN) 3 ] + complexes (SI, Figures S41–S46), as well as with one (Figure ) or two LiOTf molecules (Figure ). The LiOTf-dimer (Figure ), which may be viewed as a model of a Li-aggregate, displays bridging OTf molecules, in line with known X-ray structures . The results (Table ) confirm the same trend for all models, with Li significantly lowering the barrier of TS2, but not TS1.…”

“…The LiOTf-dimer (Figure 4), which may be viewed as a model of a Li-aggregate, displays bridging OTf molecules, in line with known X-ray structures. 85 The results (Table 2) confirm the same trend for all models, with Li significantly lowering the barrier of TS2, but not TS1. In fact, in the presence of [Li(CH 3 CN) 3 ] + or the LiOTf-dimer, the barrier of TS2 becomes lower than that of TS1 (Table 2).…”

“…It has been reported that [Li­(solvent) n ] + complexes can be formed from lithium salts containing weakly coordinating anions such as NTf 2 – , PF 6 – , BF 4 – , or BArF 4 – . , In the known crystal structures of solvated Li-complexes, the number of coordinated solvent molecules varies from 1 to 4. ,− Here, we have compared the results for nondissociated LiOTf (Figure ) as well as LiNTf 2 to the cationic solvent complexes [Li­(THF) 2 ] + and [Li­(THF) 3 ] + (SI, Figure S17–S26), to evaluate if the LA effect on the barriers is dependent on the coordination environment around Li. As Table shows, all tested LA species significantly lower the barrier of TS2 compared to the LA-free case, implying that this trend is independent of the coordination environment.…”

Anionic Effects on Li-Ion Activity and Li-Ion Intercalation Reaction Kinetics in Highly Concentrated Li Salt/Propylene Carbonate Solutions

“…Therefore, Li + ions coordinate to the anions and form CIPs. In the Raman spectra of the mixtures of [LiBF 4 ]/[PC] = 1/3 and [LiOTf]/[PC] = 1/3, intense peaks of BF 4 – and OTf – appeared at ∼775 and ∼1050 cm –1 , respectively, indicating the formation of ionic aggregates (AGGs), in which an anion is coordinated to more than one Li + ion. − This suggests that the more associative anions strongly interact with multiple Li + ions, and a certain amount of PC is removed from the first solvation sheath of Li + , resulting in an increase in the fraction of free PC in the electrolyte (vide supra).…”