Zhou Jie, Liu Xiaojing, Zhou Jianbin, Zhao Haoyu, Lin Ning, Zhu Linqin, Zhu Yongchun, Wang Gongming, Qian Yitai
Department of Applied Chemistry and National Laboratory for Physical Science at Microscale, University of Science & Technology of China, Hefei, Anhui 230026, P. R. China.
Nanoscale Horiz. 2019 Jan 1;4(1):182-189. doi: 10.1039/c8nh00289d. Epub 2018 Oct 8.
The insulating and dissoluble features of sulfur and polysulfide intermediates significantly hinder the cycling performance and coulombic efficiency of Li-S batteries. We herein design fully integrated hierarchical double-shelled CoS@CNT hollow nanospheres as a sulfur host, where each shell owns a tri-layer sandwich structure and six functional layers are constructed in total. Uniquely, the hierarchical structures integrate the beneficial functions of electrical conductivity, ion diffusion, polysulfide immobilization and polysulfide redox kinetics. The CoS@CNT/S delivers a reversible specific capacity of 1415 mA h g at 0.2C, which is very close to the theoretical capacity of sulfur. Moreover, even at a high rate of 10C, an unprecedented capacity of 676.7 mA h g can still be achieved, which represents the best rate capability among the ever-reported sulfur cathodes with similar sulfur content. More importantly, the CoS@CNT/S also displays a high coulombic efficiency of nearly 100% and an excellent cycling performance for up to 1000 cycles with a capacity fading rate of only 0.0448% per cycle. Even at the loading amount of 5.5 mg cm, the areal capacity can still reach 4.3 mA h cm. The concept to rationally integrate distinct components into fully functional units could provide valuable insights for the development of Li-S batteries and beyond.
硫及多硫化物中间体的绝缘性和溶解性显著阻碍了锂硫电池的循环性能和库仑效率。在此，我们设计了完全集成的分级双壳CoS@CNT中空纳米球作为硫宿主，其中每个壳层具有三层三明治结构，总共构建了六个功能层。独特的是，这种分级结构整合了导电性、离子扩散、多硫化物固定和多硫化物氧化还原动力学等有益功能。CoS@CNT/S在0.2C时具有1415 mA h g的可逆比容量，非常接近硫的理论容量。此外，即使在10C的高倍率下，仍可实现676.7 mA h g的前所未有的容量，这代表了在以往报道的具有相似硫含量的硫阴极中最佳的倍率性能。更重要的是，CoS@CNT/S还显示出近100%的高库仑效率和高达1000次循环的优异循环性能，容量衰减率仅为每循环0.0448%。即使在5.5 mg cm的负载量下，面积容量仍可达到4.3 mA h cm。将不同组件合理整合到全功能单元中的概念可为锂硫电池及其他电池的发展提供有价值的见解。
