71. Covalent Confinement of Sulfur Copolymers onto Graphene Sheets Affords Ultrastable Lithium-Sulfur Batteries with Fast Cathode Kinetics
writer：16. J. Ma, J. Fan, S. Chen, X. Yang, K. N. Hui, H. Zhang, C. W. Bielawski, J. Geng
keywords：sulfur copolymers, graphene, covalent binding, cathode kineties, lithium-sulfur batteries
source：期刊
Issue time：2019年
Lithium-sulfur (Li-S) batteries have received significantattention due to the high theoretical specific capacity of sulfur (1675 mA h g-1). However, the practicalapplications are often handicapped by sluggish electrochemical kinetics and the“shuttle effect” of electrochemical intermediate polysulfides. Herein, we proposean in-situ copolymerization strategy for covalently confining a sulfur-containingcopolymer onto reduced graphene oxide (RGO) to overcome the aforementionedchallenges. The copolymerization was performed by heating elemental sulfur andisopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, i.e., RGO-g-poly(S-r-IDBI), which isfeatured with 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 notonly enhances the Li+ diffusion coefficientsby nearly one order of magnitude, but also improves the mechanical propertiesof 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 elemental sulfur cathode at 0.1 C), an improved rate capacity (688mA h g-1 for RGO-g-poly(S-r-IDBI)cathode vs. 400 mA h g-1 for elemental sulfur cathodeat 1 C), and high cycling stability (a capacity decay of 0.021% per cycle, lessthan one tenth of that measured for elemental sulfur cathode).