@article{oai:ynu.repo.nii.ac.jp:00009405,
 author = {Dokko, Kaoru and Watanabe, Daiki and Ugata, Yosuke and Thomas, Morgan L. and Tsuzuki, Seiji and Shinoda, Wataru and Hashimoto, Kei and Ueno, Kazuhide and Umebayashi, Yasuhiro and Watanabe, Masayoshi},
 issue = {47},
 journal = {Journal of Physical Chemistry B},
 month = {Nov},
 note = {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 LiBF4 and sulfolane (SL). Self-diffusion coefficients of Li+ (DLi), BF4− (DBF4), and SL (DSL) were measured with pulsed field gradient NMR. In the concentrated electrolytes with molar ratios of SL/LiBF4 ≤ 3, the ratios DSL/DLi and DBF4/DLi become lower than 1, suggesting faster diffusion of Li+ than SL and BF4−, and thus the evolution of Li+ hopping conduction. X-ray crystallographic analysis of the LiBF4:SL (1:1) solvate revealed that the two oxygen atoms of the sulfone group are involved in bridging coordination of two different Li+ ions. In addition, the BF4− anion also participates in bridging coordination of Li+. Raman spectra of the highly concentrated LiBF4-SL solution suggested that Li+ ions are bridged by SL and BF4− even in the liquid state. Moreover, detailed investigation along with molecular dynamics simulations suggests that Li+ exchanges ligands (SL and BF4−) dynamically in the highly concentrated electrolytes, and Li+ hops from one coordination site to another. The spatial proximity of coordination sites, along with 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.},
 pages = {10736--10745},
 title = {Direct Evidence for Li Ion Hopping Conduction in Highly Concentrated Sulfolane-Based Liquid Electrolytes},
 volume = {122},
 year = {2018}
}