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We demonstrate that Li + hopping conduction, which cannot be explained by conventional models i.e., Onsager's theory and Stokes' law, emerges in highly concentrated liquid electrolytes composed of LiBF 4 and sulfolane (SL). Self-diffusion coefficients of Li + (D Li ), BF 4 − (D BF 4 ), and SL (D SL ) were measured with pulsed-field gradient NMR. In the concentrated electrolytes with molar ratios of SL/LiBF 4 ≤ 3, the ratios D SL /D Li and D BF 4 /D Li become lower than 1, suggesting faster diffusion of Li + than SL and BF 4 − , and thus the evolution of Li + hopping conduction. X-ray crystallographic analysis of the LiBF 4 /SL (1:1) solvate revealed that the two oxygen atoms of the sulfone group are involved in the bridging coordination of two different Li + ions. In addition, the BF 4 − anion also participates in the bridging coordination of Li + . The Raman spectra of the highly concentrated LiBF 4 −SL solution suggested that Li + ions are bridged by SL and BF 4 − even in the liquid state. Moreover, detailed investigation along with molecular dynamics simulations suggests that Li + exchanges ligands (SL and BF 4 − ) dynamically in the highly concentrated electrolytes, and Li + hops from one coordination site to another. The spatial proximity of coordination sites, along with the possible domain structure, is assumed to enable Li + hopping conduction. Finally, we demonstrate that Li + hopping suppresses concentration polarization in Li batteries, leading to increased limiting current density and improved rate capability compared to the conventional concentration electrolyte. Identification and rationalization of Li + ion hopping in concentrated SL electrolytes is expected to trigger a new paradigm of understanding for such unconventional electrolyte systems.

A new coarse-grained (CG) intermolecular force field is presented for a series of zwitterionic lipids. The model is an extension of our previous work on nonionic surfactants and is designed to reproduce experimental surface/interfacial properties as well as distribution functions from all-atom molecular dynamics (MD) simulations. Using simple functional forms, the force field parameters are optimized for multiple lipid molecules, simultaneously. The resulting CG lipid bilayers have reasonable molecular areas, chain order parameters, and elastic properties. The computed surface pressure vs. area (π-A) curve for a DPPC monolayer demonstrates a significant improvement over the previous CG models. The DPPC monolayer has a longer persistence length than a PEG lipid monolayer, exhibiting a long-lived curved monolayer surface under negative tension. The bud ejected from an oversaturated DPPC monolayer has a large bicelle-like structure, which is different from the micellar bud formed from an oversaturated PEG lipid monolayer. We have successfully observed vesicle formation during CG-MD simulations, starting from an aggregate of DMPC molecules. Depending on the aggregate size, the lipid assembly spontaneously transforms into a closed vesicle or a bicelle. None of the various intermediate structures between these extremes seem to be stable. An attempt to observe fusion of two vesicles through the application of an external adhesion force was not successful. The present CG force field also supports stable multi-lamellar DMPC vesicles.