Multifunctional Cellulose Nanocrystals as a High-Efficient Polysulfide Stopper for Practical Li–S Batteries
Jie Liu, Yanyan Li, Yuxue Xuan, Liujiang Zhou, Dong Wang, Zhenwei Li, Haifeng Lin, Sergei Tretiak, Hui Wang, Lei Wang, Ziyang Guo, Shanqing Zhang
Abstract
Because of the severe shuttle effect of polysulfides, achieving durable Li–S batteries is still a great challenge, especially under practical operation conditions including the high sulfur content, high loading, and high operation temperature. Herein, for the first time, low-cost, eco-friendly, and hydrophilic cellulose nanocrystals (CNCs) are proposed as a multifunctional polysulfide stopper for Li–S batteries with high performance. CNCs display an intrinsically high aspect ratio and a large surface area and contain a large amount of hydroxyl groups offering a facile platform for chemical interactions. Density functional theory calculations suggest that the electron-rich functional groups on CNCs deliver robust binding energies with polysulfides. In this work, CNCs not only firmly confine sulfur and polysulfides in the cathode as a robust binder, but also further hinder polysulfide shuttling to the Li anode as a polysulfide stopper on a separator. Consequently, the as-prepared Li–S batteries demonstrate outstanding cycling performance even under the conditions of high sulfur content of 90 wt % (63 wt % in the cathode), high loading of 8.5 mg cm–2, and high temperature of 60 °C. These results sufficiently demonstrate that CNCs have significant application potential in Li–S battery technologies.