title: Hierarchical sulfur-based cathode materials with long cycle life for rechargeable lithium batteries.
abstract: Composite materials of porous pyrolyzed polyacrylonitrile-sulfur@graphene nanosheet (pPAN-S@GNS) are fabricated through a bottom-up strategy. Microspherical particles are formed by spray drying of a mixed aqueous colloid of PAN nanoparticles and graphene nanosheets, followed by a simple heat treatment with elemental sulfur. The pPAN-S primary nanoparticles are wrapped homogeneously and loosely within a three-dimensional network of graphene nanosheets (GNS). The hierarchical pPAN-S@GNS composite shows a high reversible capacity of 1449.3 mAh g(-1) sulfur or 681.2 mAh g(-1) composite in the second cycle; after 300 cycles at a 0.2 C charge/discharge rate the capacity retention is 88.8 % of its initial reversible value. Additionally, the coulombic efficiency (CE) during cycling is near 100 %, apart from in the first cycle, in which CE is 81.1 %. A remarkable capacity of near 700 mAh g(-1) sulfur is obtained, even at a high discharge rate of 10 C. The superior performance of pPAN-S@GNS is ascribed to the spherical secondary GNS structure that creates an electronically conductive 3D framework and also reinforces structural stability.
authors.affiliation: Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (PR China). wangjiulin@sjtu.edu.cn.
authors.forename: Jiulin
authors.initials: J
authors.lastname: Wang
authors.forename: Lichao
authors.initials: L
authors.lastname: Yin
authors.forename: Hao
authors.initials: H
authors.lastname: Jia
authors.forename: Haitao
authors.initials: H
authors.lastname: Yu
authors.forename: Yushi
authors.initials: Y
authors.lastname: He
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Charles W
authors.initials: CW
authors.lastname: Monroe
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D006108:Graphite / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D008863:Microspheres; D013455:Sulfur / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; C010504:polyacrylonitrile; D013455:Sulfur; D006108:Graphite; D008094:Lithium
keywords: electrochemistry; graphene; nanostructures; rechargeable Li-S batteries; sulfur composite