Suppressing the dissolution of polysulfides with cosolvent fluorinated diether towards high-performance lithium sulfur batteries

Abstract

The dissolution and shuttle of polysulfides in electrolytes cause severe anode corrosion, low coulombic efficiency, and a rapid fading of the capacity of lithium-sulfur batteries. Fluorinated diether (FDE) was selected as a cosolvent in traditional ether electrolytes to suppress the dissolution of polysulfides. The modified electrolytes lead to a negligible solubility of polysulfides, as well as decreased corrosion of the lithium anode. In an optimal system, the cells show improved cycling performance with an average coulombic efficiency of above 99% and a highly stable reversible discharge capacity of 701 mA h g after 200 cycles at a 0.5C rate. A combination of electrochemical studies and X-ray photoelectron spectroscopy demonstrates the sulfur reduction mechanism with three voltage plateaus.

Halide‐Based Materials and Chemistry for Rechargeable Batteries

“…Thet ypical design strategy involves adding fluorinated organic compounds such as fluorinated boronic esters, fluorinated ethers,f luorinated carbonates,a nd fluorinated alkylphosphates to the electrolyte. [79,[138][139][140][141][142] Of these,t he fluorinated boronic ester was found to be ad ual-functional additive,o ffering protection against over-charge as well as anion acceptor for lithium-ion batteries. [138] Zhang and coworkers reported that the use of fluorinated carbonate solvents contributed to the formation of ah igh-voltage electrolyte that produced fewer solid decomposition products on the surface of the anode (graphite,Li, or Li 4 Ti 5 O 12 )and the LiNi 0.5 Mn 1.5 O 4 cathode.T hese properties significantly improved the cycling stability at elevated temperatures.…”

Anode Interface Engineering and Architecture Design for High‐Performance Lithium–Sulfur Batteries

“…Fluorinated ethers have also received attention for using in electrolytes due to their low viscosity, low melting point, high oxidation potential, low flammability, and the low solubility of polysulfides in fluorinated ethers. [38a] Fluorinated ethers such as 1,1,2,2‐tetrafluoro‐3‐(1,1,2,2‐tetrafluoroethoxy)propane,[38a] bis(2,2,2‐trifluoroethyl) ether, 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether,[38b,c,55] ethyl 1,1,2,2‐tetrafluoroethyl ether, 1,1,2,2‐tetrafluoroethyl‐2,2,2‐trifluoroethyl ether, and 1,3‐(1,1,2,2‐tetrafluoroethoxy)propane have been developed as co‐solvents to facilitate the formation of LiF‐rich layers on the anodes surface, suppressing the shuttle effect of polysulfides and improving the electrochemical performance of Li–S batteries.…”

Spiderweb‐Mimicking Anion‐Exchanging Separators for Li–S Batteries

“…Subsequently, the resultant PVIm[TFSI] was put into a pristine electrolyte solution (1 m LiTFSI in DOL/DME = 1/1 v/v, without polysulfides) for 24 h and the change in the UV–vis spectra of the electrolyte solution was monitored. The electrolyte solution containing the polysulfide‐trapped PVIm[TFSI] showed a characteristic absorption peak at ≈280 nm in contrast to the pristine electrolyte solution (Figure d), exhibiting the release of polysulfides from the PVIm[TFSI]. The abovementioned results demonstrated that the PVIm[TFSI] synthesized herein undergoes a diffusion‐driven anion exchange reaction with polysulfides, which is expected to enable the reversible trap/release of polysulfides during charge/discharge cycling in Li–S batteries.…”

“…As additional evidence to verify the polysulfide‐capturing capability of PVIm[TFSI], UV–vis absorption spectra of the polysulfide solution were examined as a function of PVIm[TFSI] concentration (Figure c). The intensity of the characteristic peak around wavelength of 280 nm, which is ascribed to S 6 2− and S 8 2− species, became weakened with the increase of PVIm[TFSI] concentration, which indicated a decrease in the polysulfide content in the solution.…”