title: Enhanced Li-S Batteries Using Amine-Functionalized Carbon Nanotubes in the Cathode.
abstract: The rechargeable lithium-sulfur (Li-S) battery is an attractive platform for high-energy, low-cost electrochemical energy storage. Practical Li-S cells are limited by several fundamental issues, including the low conductivity of sulfur and its reduction compounds with Li and the dissolution of long-chain lithium polysulfides (LiPS) into the electrolyte. We report on an approach that allows high-performance sulfur-carbon cathodes to be designed based on tethering polyethylenimine (PEI) polymers bearing large numbers of amine groups in every molecular unit to hydroxyl- and carboxyl-functionalized multiwall carbon nanotubes. Significantly, for the first time we show by means of direct dissolution kinetics measurements that the incorporation of CNT-PEI hybrids in a sulfur cathode stabilizes the cathode by both kinetic and thermodynamic processes. Composite sulfur cathodes based the CNT-PEI hybrids display high capacity at both low and high current rates, with capacity retention rates exceeding 90%. The attractive electrochemical performance of the materials is shown by means of DFT calculations and physical analysis to originate from three principal sources: (i) specific and strong interaction between sulfur species and amine groups in PEI; (ii) an interconnected conductive CNT substrate; and (iii) the combination of physical and thermal sequestration of LiPS provided by the CNT=PEI composite.
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Lin
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Houlong L
authors.initials: HL
authors.lastname: Zhuang
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Shuya
authors.initials: S
authors.lastname: Wei
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Kenville E
authors.initials: KE
authors.lastname: Hendrickson
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Mun Sek
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Gil
authors.initials: G
authors.lastname: Cohn
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hennig
authors.affiliation: Department of Materials Science & Engineering and ‡Department of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Lynden A
authors.initials: LA
authors.lastname: Archer
keywords: lithium−nitrile interactions; lithium−sulfur batteries; molecular sorbents; sequestering lithium polysulfide