Zhang Heng, Yang Li, Zhang Peigen, Lu Chengjie, Sha Dawei, Yan Bingzhen, He Wei, Zhou Min, Zhang Wei, Pan Long, Sun ZhengMing
Key Laboratory of Advanced Metallic Materials of Jiangsu Province, School of Materials Science and Engineering, Southeast University, Nanjing, 211189, P. R. China.
Hefei National Laboratory for Physical Sciences at the Microscale, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, 230026, P. R. China.
Adv Mater. 2021 May;33(21):e2008447. doi: 10.1002/adma.202008447. Epub 2021 Apr 17.
The application of Li-S batteries has been hindered by the shuttling behavior and sluggish reaction kinetics of polysulfides. Here an effective polysulfide immobilizer and catalytic promoter is developed by proposing oxygen-vacancy-rich Ti O quantum dots (OV-T QDs) decorated on porous carbon nanosheets (PCN), which are modulated using Ti C T MXene as starting materials. The T QDs not only confine polysulfides through strong chemisorption but also promote polysulfide conversion via redox-active catalysis. The introduction of oxygen vacancies further boosts the immobilization and conversion of polysulfides by lowering the adsorption energy and shortening the bond lengths. The PCN provides a physical polysulfide confinement as well as a flexible substrate preventing OV-T QDs from aggregation. Moreover, the two building blocks are conductive, thereby effectively improving the electron/charge transfer. Finally, the ultrasmall size of QDs along with the porous structure endows OV-T QDs@PCN with large specific surface area and pore volume, affording adequate space for S loading and volume expansion. Therefore, the OV-T QDs@PCN/S delivers a high S loading (79.1 wt%), good rate capability (672 mA h g at 2 C), and excellent long-term cyclability (88% capacity retention over 1000 cycles at 2 C). It also exhibits good Li storage under high S-mass loading and lean electrolyte.
锂硫电池的应用受到多硫化物穿梭行为和缓慢反应动力学的阻碍。在此，通过以Ti₃C₂Tₓ MXene为起始材料制备负载富氧空位的TiO₂量子点（OV-TiO₂ QDs）修饰的多孔碳纳米片（PCN），开发了一种有效的多硫化物固定剂和催化促进剂。TiO₂ QDs不仅通过强化学吸附作用限制多硫化物，还通过氧化还原活性催化促进多硫化物转化。氧空位的引入通过降低吸附能和缩短键长进一步增强了多硫化物的固定和转化。PCN提供了物理上对多硫化物的限制以及防止OV-TiO₂ QDs聚集的柔性基底。此外，这两个结构单元具有导电性，从而有效改善了电子/电荷转移。最后，量子点的超小尺寸以及多孔结构赋予OV-TiO₂ QDs@PCN较大的比表面积和孔体积，为硫负载和体积膨胀提供了足够的空间。因此，OV-TiO₂ QDs@PCN/S具有高硫负载量（79.1 wt%）、良好的倍率性能（2 C下为672 mA h g）以及出色的长期循环稳定性（2 C下1000次循环后容量保持率为88%）。在高硫质量负载和贫电解质条件下，它也表现出良好的锂存储性能。
