Solvation structure of Li⁺ in highly concentrated LiTFSA–DMSO solutions studied by means of neutron diffraction with ⁶Li/⁷Li isotopic substitution method.

This article focuses on elucidating the solvation structure of lithium ions (Li⁺) in highly concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSA)–dimethyl sulfoxide (DMSO) solutions using time-of-flight neutron diffraction combined with ^6Li/^7Li isotopic substitution. The study reveals that in a 20 mol% LiTFSA–DMSO-d₆ solution, each Li⁺ ion is coordinated by approximately 4.1 DMSO molecules in its first solvation shell, with a Li⁺–O_DMSO distance of 1.96(3) Å and a bond angle of 138(15)°. These findings confirm and refine previous Raman spectroscopic results and provide detailed microscopic structural information relevant to the development of stable, high-performance lithium-ion and Li–O₂ battery electrolytes. The research also notes the absence of direct Li⁺–TFSA⁻ contact ion pairs in this concentration range and suggests further neutron diffraction studies at higher concentrations to explore such interactions.