Improving Rate Performance of Encapsulating Lithium‐Polysulfide Electrolytes for Practical Lithium−Sulfur Batteries

Abstract The cycle life of high‐energy‐density lithium−sulfur (Li−S) batteries is severely plagued by the incessant parasitic reactions between Li metal anodes and reactive Li polysulfides (LiPSs). Encapsulating Li‐polysulfide electrolyte (EPSE) emerges as an effective electrolyte design to mitigate the parasitic reactions kinetically. Nevertheless, the rate performance of Li−S batteries with EPSE is synchronously suppressed. Herein, the sacrifice in rate performance by EPSE is circumvented while mitigating parasitic reactions by employing hexyl methyl ether (HME) as a co‐solvent. The specific capacity of Li−S batteries with HME‐based EPSE is nearly not decreased at 0.1 C compared with conventional ether electrolytes. With an ultrathin Li metal anode (50 μm) and a high‐areal‐loading sulfur cathode (4.4 mg S cm −2 ), a longer cycle life of 113 cycles was achieved in HME‐based EPSE compared with that of 65 cycles in conventional ether electrolytes at 0.1 C. Furthermore, both high energy density of 387 Wh kg −1 and stable cycle life of 27 cycles were achieved in a Li−S pouch cell (2.7 Ah). This work inspires the feasibility of regulating the solvation structure of LiPSs in EPSE for Li−S batteries with balanced performance.