title: One-pot pyrolysis of lithium sulfate and graphene nanoplatelet aggregates: in situ formed Li₂S/graphene composite for lithium-sulfur batteries.
abstract: Lithium sulfide (Li2S) as a cathodic material in Li-S batteries can not only deliver a high theoretical specific capacity of 1166 mA h g(-1), but also is essential for batteries using Li-free anode materials such as silicon and graphite. Various efforts have been made to synthesize a highly efficient Li2S-carbon composite; however, the electronically and ionically insulating nature and high melting point of Li2S strongly complicate the synthetic procedures, making it difficult to realize the expected capacity. Herein, a very simple method is proposed to prepare Li2S/graphene composites by one-pot pyrolysis of a mixture of graphene nanoplatelet aggregates (GNAs) and low-cost lithium sulfate (Li2SO4). For the first time, the entire pyrolysis process is clarified by thermogravimetry-mass spectrometry, wherein GNAs were found to partly serve as a carbon source to reduce Li2SO4 to Li2S, while the remaining GNAs formed thin graphene sheets as a result of this in situ etching, as a highly conductive host can immobilize the generated Li2S by intimate contact. Consequently, the obtained Li2S/graphene composite, combined with a Li2Sx-insoluble (x = 4-8) electrolyte developed by our group, exhibits excellent electrochemical behavior for Li-S batteries.
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan. mwatanab@ynu.ac.jp.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Li
authors.forename: Shiguo
authors.initials: S
authors.lastname: Zhang
authors.forename: Ce
authors.initials: C
authors.lastname: Zhang
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Ueno
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yasuda
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Tatara
authors.forename: Kaoru
authors.initials: K
authors.lastname: Dokko
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Watanabe