Hydrofluoroether

About: Hydrofluoroether is a research topic. Over the lifetime, 289 publications have been published within this topic receiving 2873 citations. The topic is also known as: hydrofluoroethers & HFE.

Extremely Stable Sodium Metal Batteries Enabled by Localized High-Concentration Electrolytes

Abstract: Sodium (Na) metal is a promising anode for Na-ion batteries. However, the high reactivity of Na metal with electrolytes and the low Na metal cycling efficiency have limited its practical application in rechargeable Na metal batteries. High-concentration electrolytes (HCE, ≥4 M) consisting of sodium bis(fluorosulfonyl)imide (NaFSI) and ether solvent could ensure the stable cycling of Na metal with high Coulombic efficiency but at the cost of high viscosity, poor wettability, and high salt cost. Here, we report that the salt concentration could be significantly reduced (≤1.5 M) by a hydrofluoroether as an “inert” diluent, which maintains the solvation structures of HCE, thereby forming a localized high-concentration electrolyte (LHCE). A LHCE [2.1 M NaFSI/1,2-dimethoxyethane (DME)–bis(2,2,2-trifluoroethyl) ether (BTFE) (solvent molar ratio 1:2)] enables dendrite-free Na deposition with a high Coulombic efficiency of >99%, fast charging (20C), and stable cycling (90.8% retention after 40 000 cycles) of Na∥Na...

Unique behaviour of nonsolvents for polysulphides in lithium–sulphur batteries

Abstract: Combination of a solvent–salt complex [acetonitrile(ACN)2–LiTFSI] with a hydrofluoroether (HFE) co-solvent unveil a new class of Li–S battery electrolytes. They possess stability against Li metal and viscosities which approach that of conventional ethers, but they have the benefit of low volatility and minimal solubility for lithium polysulphides while exhibiting an uncharacteristic sloping voltage profile. In the optimal system, cells can be discharged to full theoretical capacity under quasi-equilibrium conditions while sustaining high reversible capacities (1300–1400 mA h g−1) at moderate rates, and capacities of 1000 mA h g−1 with almost no capacity fade at fast discharge rates under selected cycling protocols. A combination of operando X-ray absorption spectroscopy at the S K-edge, and electrochemical studies demonstrate that lithium polysulphides are indeed formed in these ACN-complexed systems. Their limited dissolution and mobility in the electrolyte strongly affect the speciation and polysulphide equilibria, leading to controlled precipitation of Li2S.

Solvent Activity in Electrolyte Solutions Controls Electrochemical Reactions in Li-Ion and Li-Sulfur Batteries

Abstract: Solvent–ion and ion–ion interactions have significant effects on the physicochemical properties of electrolyte solutions for lithium batteries. The solvation structure of Li+ and formation of ion pairs in electrolyte solutions composed of triglyme (G3) and a hydrofluoroether (HFE) containing 1 mol dm–3 Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl)amide) were analyzed using pulsed-field gradient spin–echo (PGSE) NMR and Raman spectroscopy. It was found that Li+ is preferentially solvated by G3 and forms a [Li(G3)]+ complex cation in the electrolytes. The HFE scarcely participates in the solvation because of low donor ability and relatively low permittivity. The dissociativity of Li[TFSA] decreased as the molar ratio of G3/Li[TFSA] in the solution decreased. The activity of G3 in the electrolyte diminishes negligibly as the molar ratio approaches unity because G3 is involved in 1:1 complexation with Li+ ions. The negligible activity of G3 in the electrolyte solutions has significant effects on the electroch...

Li+ Solvation and Ionic Transport in Lithium Solvate Ionic Liquids Diluted by Molecular Solvents

Abstract: An equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and either triglyme (G3) or tetraglyme (G4) yielded stable molten complexes: [Li(G3)][TFSA] and [Li(G4)][TFSA]. These are known as solvate ionic liquids (SILs). Glyme-based SILs have thermal and electrochemical properties favorable for use as lithium-conducting electrolytes in lithium batteries. However, their intrinsically high viscosities and low ionic conductivities prevent practical application. Therefore, we diluted SILs with molecular solvents in order to enhance their ionic conductivities. To determine the stabilities of the complex cations in diluted SILs, their conductivity and viscosity, the self-diffusion coefficients, and Raman spectra were measured. [Li(G3)]+ and [Li(G4)]+ were stable in nonpolar solvents, that is, toluene, diethyl carbonate, and a hydrofluoroether (HFE); however, ligand exchange took place between glyme and solvent when polar solvents, that is, water and propylene carbonate, were used. In acetonitr...

Acid-Sensitive Semiperfluoroalkyl Resorcinarene: An Imaging Material for Organic Electronics

Abstract: An acid-sensitive semiperfluoroalkyl resorcinarene was synthesized, and its lithographic properties were evaluated. Its solubility in segregated hydrofluoroether solvents enables the patterning of delicate organic electronic materials.