Polysulfide Rejection Strategy in Lithium-Sulfur Batteries Using an Ion-Conducting Gel-Polymer Interlayer Membrane

Lithium-sulfur batteries (LiSBs) are emergingas promisingalternative to conventional secondary lithium-ion batteries (LiBs)due to their high energy density, low cost, and environmental friendliness.However, preventing polysulfide dissolution is a great challenge fortheir commercial viability. The present work is focused on preparinga lithium salt and ionic liquid (IL) solution (SIL) impregnated ion(lithium ion)-conducting gel-polymer membrane (IC-GPM) interlayerto prevent polysulfide migration toward the anode by using an electrostaticrejection and trapping strategy. Herein, we introduce an SIL-basedfreestanding optimized IC-GPM70 (70 wt % SIL) interlayer membranewith high lithium-ion conductivity (2.58 x 10(-3) S cm(-1)) along with excellent thermal stabilityto suppress the migration of polysulfide toward the anode and preventpolysulfide dissolution in the electrolyte. Because of the coulombicinteraction, the anionic groups, -CF2 of the & beta;-phasepolymer host PVdF-HFP, TFSI- anion of IL EMIMTFSI,and anion BOB- of LIBOB salt, allow hopping of positivelycharged lithium ions (Li+) but reject negatively chargedand relatively large-sized polysulfide anions (S (x) (-2), 4 <x <8). Thecationic group EMIM+ of the IL is electrostatically ableto attract and trap the polysulfides in the interlayer membrane. Sincethe shuttle effect of lithium polysulfides in LiSBs has been suppressedby the prepared IC-GPM70 interlayer, the resulting lithium-sulfurcell exhibits significantly higher cycling stability (1200 cycles),rate performance (1343, 1208, 1043, 875, and 662 mAh g(-1) at 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively), and structural integrityduring cycling than its counterpart without the IC-GPM70 interlayer.The interlayer membrane has been found to improve the performanceand durability of LiSBs, thus making them a viable alternative toconventional LiBs.