Fast redox conversion in lithium-sulfur batteries enabled by Cu-doped W₁₈O₄₉ with abundant oxygen defects

Lithium-sulfur (Li//S) batteries constitute promising high energy storage devices but suffer from serious Li polysulfide (LiPS) shuttle effect and sluggish redox conversion. Herein, we report that these challenges can be tackled successfully by introducing oxygen defects in W(18)O(49)via Cu doping. The oxygen defects in Cu-dopedW(18)O(49) (Cu/W18O49) are critical not only for enhancing the chemosorption toward LiPS but also for promoting the electrocatalytic conversion of LiPS. A reaction pathway for electrocatalytic conversion of LiPS to Li2S2/Li2S is proposed based on various analyses. As a result, the Cu/W18O49 modified PP (Cu/W18O49@PP) separator with a thin composite layer of 2.3 mu m and 0.25 mg cm(-2 )displays high ionic conductivity, fast Li+ ion transport and super-electrolyte-philicity. The Li//S battery with the Cu/W18O49@PP separator shows superior cycling stability with a low capacity decay rate of 0.046% per cycle at 1 C over 300 cycles, up to 5 C discharge rate, and ultralow self-discharge behavior. Our work provides fresh insights into the design of electrocatalysts for fast redox conversion in advanced Li//S batteries.