Sulfur-inserted polymer-anchored EExG electrode meets the conflicting requirement of physically restraining sulfur dissolution while maintaining structural flexibility to cope with the volume expansion of sulfur during the charge–discharge cycles.

To further improve the energy density and safety of Li-ion batteries (LIBs), multifunctional electrolyte solvents are needed to replace conventional carbonate solvents. In this study, a nonflammable fluorinated ester, methyl 3,3,3-trifluoropropionate (MTFP), is evaluated as an electrolyte solvent for high-voltage Li batteries with the LiCoO2 positive electrode. A Li/LiCoO2 cell with an MTFP-based electrolyte exhibits superior capacity retention compared with a cell with a conventional carbonate-based electrolyte with a cutoff voltage of 4.5 V. Moreover, the LiCoO2 composite electrode with sodium carboxymethyl cellulose and styrene-butadiene rubber as binders, instead of the commonly used poly(vinylidene fluoride), can be cycled in the MTFP-based electrolyte without capacity loss or increase in polarization under high-voltage operation. The low-temperature performance and thermal stability of the LiCoO2 electrode are also improved by using the MTFP-based electrolyte. The analysis by X-ray photoelectron spectroscopy of the LiCoO2 electrode cycled in the MTFP-based electrolyte suggests that a thin and uniform passivation layer is formed on the electrode surface, resulting in excellent cyclability and thermal stability for LiCoO2. The insights related to nonflammable electrolytes contribute to the development of high-energy LIBs without sacrificing safety.

Lithium-sulfur (LiÀ S) batteries have attracted remarkable attention as next-generation batteries due to their low cost and high theoretical specific energy density. However, they have encountered several difficulties, including low specific capacity due to the insulating nature of sulfur as well as poor cycle performance. Here, we introduce the LiÀ S batteries using metaldeposited graphite as a positive electrode, together with S 8 and Li 2 S 8 as active materials to achieve high initial discharge capacity and improved cyclability. Galvanostatic charge-discharge measurements for the S 8 -impregnated electrode highlight the positive effect of Au additives on the initial discharge capacity (mAh cm À 3 ); 48.1 (G) < 56.1 (Ag/G) < 84.1 (Au/G). Fur-thermore, improved cyclability was observed for the Audecorated electrode with a Li 2 S 8 catholyte system; capacity retention rate was in order of Ag/G < G < Au/G. The validity of the design strategy for both electrode and active material was confirmed by observing the highest discharge capacity at the 50th cycle for Au-decorated electrode (84.8 mAh cm À 3 ) using both S 8 and Li 2 S 8 active materials. We concluded that (1) the enhanced electrochemical solid⇄liquid conversion of sulfur and (2) high sulfur affinity of Au particle enabled the efficient utilization of insulated solid sulfur active materials (S 8 and Li 2 S) as well as liquid lithium polysulfide intermediates, contributing to the high initial discharge capacity and better cyclability.

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