Stabilizing Lithium-Sulfur Cells with Practical Loading and Cycling Conditions Using Li 2 S 8 -Containing Ethereal Electrolyte Solution

Abstract

We report on stabilization of Li–S cells cycled with an areal charge/discharge capacity of 2 mAh cm −2 at current densities of 1–2 mA cm −2 using ethereal LiTFSI/LiNO 3 /DOL/DME electrolyte solution containing 0.1M Li 2 S 8 . This electrolyte solution enables stable lithium metal stripping−plating both in symmetric Li∣Li and full Li–S cells with composite binder free sulfur impregnated activated carbon fibers cathodes. The addition of Li 2 S 8 substantially extends cycling life of these cells due to the formation of smooth non-dendritic Li metal surface protected with an effective SEI enriched with Li sulfides, sulfites and sulfates species. Symmetric Li∣Li could be cycled stably for more than 1000 h at 1–2 mA cm −2 with Li 2 S 8 -containing electrolyte solutions. Full Li–S cells demonstrate more than 500 stable cycles (at least 3 times more than with Li 2 S 8 free electrolyte solution) at a current density of 1 mA cm −2 and an areal capacity of 2 mAh cm −2 . The most stable cycling results were achieved for the cells cycled with discharge cut off voltage of 1.9 V preventing the depletion of LiNO 3 . The use of electrolyte solutions containing liquid lithium poly-sulfides makes possible considerable decrease in the amount of the electrolyte solution and increases the energy density of the cells.