The quinone-based conjugated microporous polymer as an effective electrode additive for activated graphene host material in lithium-sulfur batteries

Lithium-Sulfur (Li-S) battery is receiving increasing attention for next-generation energy storage system due to its promising features such as high theoretical energy density and cost-effectiveness. However, sluggish redox reaction and fatal polysulfide dissolution have been considered as significant challenges which limit the practical application of Li-S batteries. Recently, anthraquinone-based organic molecule was used in the Li-S battery and exhibited good electrochemical performance with enhanced redox chemistry and structural stability. Herein, we used anthraquinone-based conjugated microporous polymer (CMP), namely PAQTA, as an electrode additive for activated graphene (AG) host material in Li-S batteries. Conjugated network of PAQTA with high surface area and porosity provided efficient redox activity and stable electrochemical performance compared to non-conjugated quinone material. We prepared reduced AG/sulfur (rAG/S) electrodes by varying amounts of PAQTA addition and the optimized rAG1h/S + PAQTA 5% showed the best electrochemical performance, proving a synergistic effect between rAG and PAQTA additive. In detail, rAG act as effective host material by taking advantage of in-plane nanopores and high surface area, resulting in enhanced polysulfide adsorption. The PAQTA additive, which improves redox kinetic, could further make intimate contact with rAG via π–π stacking interaction, thereby enhancing the cycling stability. Thus, it is important to note that the synergistic effect between AG host and PAQTA additive enabled improved redox chemistry and structural stability for good electrochemical performance. This study suggests the usage of PAQTA as effective electrode additive for high-performance Li-S batteries with improved long-term cycling stability.