Effect of Hydrofluoroether Cosolvent Addition on Li Solvation in Acetonitrile-Based Solvate Electrolytes and Its Influence on S Reduction in a Li–S Battery

• DOI: 10.1021/acsami.6b11358
• Publication Date: 2016-11-16T16:21:04Z
• Authors: Kimberly A. See; Heng-Liang Wu; Kah Chun Lau; Minjeong Shin; Lei Cheng; Mahalingam Balasu...; Kevin G. Gallagher; Larry A. Curtiss; Andrew A. Gewirth
• Keywords: Polysulfide

Li-S batteries are a promising next-generation battery technology. Due to the formation of soluble polysulfides during cell operation, electrolyte composition plays an active role in directing and speciation lithium polysulfides. Recently, new classes electrolytes termed "solvates" that contain stoichiometric quantities salt solvent form liquid at room temperature have been explored due their sparingly solvating properties with respect The viscosity solvate is understandably high limiting viability; however, hydrofluoroether cosolvents, thought be inert structure itself, can introduced reduce enhance diffusion. Nazar co-workers previously reported addition 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) LiTFSI acetonitrile solvate, (MeCN)2-LiTFSI, results enhanced capacity retention compared neat solvate. Here, we evaluate effect TTE on both electrochemical behavior solvation (MeCN)2-LiTFSI electrolyte. Contrary previous suggestions, Raman NMR spectroscopy coupled ab initio molecular dynamics simulations show coordinates Li+ expense MeCN coordination, thereby producing higher content free MeCN, good polysulfide solvent, containing facilitate faster kinetics reduction S likely as result power MeCN.