Ma Junpeng, Fan Jingbiao, Chen Shang, Yang Xinyue, Hui Kwun Nam, Zhang Hongwen, Bielawski Christopher W, Geng Jianxin
Experimental Teaching Center, School of Materials Science and Engineering , Changzhou University , Changzhou , Jiangsu 213100 , China.
College of Energy, State Key Laboratory of Organic-Inorganic Composites , Beijing University of Chemical Technology , 15 North Third Ring East Road , Chaoyang District, Beijing 100029 , China.
ACS Appl Mater Interfaces. 2019 Apr 10;11(14):13234-13243. doi: 10.1021/acsami.9b00214. Epub 2019 Mar 29.
Lithium-sulfur (Li-S) batteries have received significant attention due to the high theoretical specific capacity of sulfur (1675 mA h g). However, the practical applications are often handicapped by sluggish electrochemical kinetics and the "shuttle effect" of electrochemical intermediate polysulfides. Herein, we propose an in-situ copolymerization strategy for covalently confining a sulfur-containing copolymer onto reduced graphene oxide (RGO) to overcome the aforementioned challenges. The copolymerization was performed by heating elemental sulfur and isopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, that is, RGO- g-poly(S- r-IDBI), which is featured by a high sulfur content and uniform distribution of the poly(S- r-IDBI) on RGO sheets. The covalent confinement of poly(S- r-IDBI) onto RGO sheets not only enhances the Li diffusion coefficients by nearly 1 order of magnitude, but also improves the mechanical properties of the cathodes and suppresses the shuttle effect of polysulfides. As a result, the RGO- g-poly(S- r-IDBI) cathode exhibits an enhanced sulfur utilization rate (10% higher than that of an elemental sulfur cathode at 0.1C), an improved rate capacity (688 mA h g for the RGO- g-poly(S- r-IDBI) cathode vs 400 mA h g for an elemental sulfur cathode at 1C), and a high cycling stability (a capacity decay of 0.021% per cycle, less than one-tenth of that measured for an elemental sulfur cathode).
锂硫（Li-S）电池因硫的理论比容量高（1675 mA h g）而备受关注。然而，实际应用常常受到缓慢的电化学动力学和电化学中间体多硫化物的“穿梭效应”的阻碍。在此，我们提出一种原位共聚策略，将含硫共聚物共价限制在还原氧化石墨烯（RGO）上，以克服上述挑战。通过加热元素硫和异丙烯基苯基功能化的RGO进行共聚反应，得到一种含硫共聚物，即RGO-g-聚（S-r-IDBI），其特点是硫含量高且聚（S-r-IDBI）在RGO片上分布均匀。聚（S-r-IDBI）在RGO片上的共价限制不仅使锂扩散系数提高了近1个数量级，还改善了阴极的机械性能并抑制了多硫化物的穿梭效应。结果，RGO-g-聚（S-r-IDBI）阴极表现出提高的硫利用率（在0.1C时比元素硫阴极高10%）、改善的倍率性能（在1C时，RGO-g-聚（S-r-IDBI）阴极的容量为688 mA h g，而元素硫阴极的容量为400 mA h g）以及高循环稳定性（每循环容量衰减0.021%，不到元素硫阴极测量值的十分之一）。
