title: Heterogeneous WSx/WO₃ Thorn-Bush Nanofiber Electrodes for Sodium-Ion Batteries.
abstract: Heterogeneous electrode materials with hierarchical architectures promise to enable considerable improvement in future energy storage devices. In this study, we report on a tailored synthetic strategy used to create heterogeneous tungsten sulfide/oxide core-shell nanofiber materials with vertically and randomly aligned thorn-bush features, and we evaluate them as potential anode materials for high-performance Na-ion batteries. The WSx (2 ≤ x ≤ 3, amorphous WS3 and crystalline WS2) nanofiber is successfully prepared by electrospinning and subsequent calcination in a reducing atmosphere. To prevent capacity degradation of the WSx anodes originating from sulfur dissolution, a facile post-thermal treatment in air is applied to form an oxide passivation surface. Interestingly, WO3 thorn bundles are randomly grown on the nanofiber stem, resulting from the surface conversion. We elucidate the evolving morphological and structural features of the nanofibers during post-thermal treatment. The heterogeneous thorn-bush nanofiber electrodes deliver a high second discharge capacity of 791 mAh g(-1) and improved cycle performance for 100 cycles compared to the pristine WSx nanofiber. We show that this hierarchical design is effective in reducing sulfur dissolution, as shown by cycling analysis with counter Na electrodes.
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Won-Hee
authors.initials: WH
authors.lastname: Ryu
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Hope
authors.initials: H
authors.lastname: Wilson
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University , Prospect Street, New Haven, Connecticut 06511, United States.
authors.forename: Sungwoo
authors.initials: S
authors.lastname: Sohn
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Jinyang
authors.initials: J
authors.lastname: Li
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Xiao
authors.initials: X
authors.lastname: Tong
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Evyatar
authors.initials: E
authors.lastname: Shaulsky
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University , Prospect Street, New Haven, Connecticut 06511, United States.
authors.forename: Jan
authors.initials: J
authors.lastname: Schroers
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Menachem
authors.initials: M
authors.lastname: Elimelech
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: André D
authors.initials: AD
authors.lastname: Taylor
keywords: electrospinning; heterogeneous structure; nanofiber; sodium-ion batteries; tungsten sulfide