title: Core-Shell Structure and Interaction Mechanism of γ-MnO2Coated Sulfur for Improved Lithium-Sulfur Batteries.
abstract: Lithium-sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g-1and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core-shell γ-MnO2-coated sulfur nanocomposite through the redox reaction between KMnO4and MnSO4. The multifunctional MnO2shell facilitates electron and Li+transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ-MnO2crystallographic form also provides one-dimensional (1D) tunnels for the Li+incorporation to alleviate insoluble Li2S2/Li2S deposition at high discharge rate. More importantly, the MnO2phase transformation to Mn3O4occurs during the redox reaction between polysulfides and γ-MnO2is first thoroughly investigated. The S@γ-MnO2composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn3O4phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li-S cells.
authors.affiliation: College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Lubin
authors.initials: L
authors.lastname: Ni
authors.affiliation: College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Gangjin
authors.initials: G
authors.lastname: Zhao
authors.affiliation: College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Sun
authors.affiliation: Testing Center, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Chuanqiang
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Testing Center, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: XiangXiang
authors.initials: X
authors.lastname: Gong
authors.affiliation: College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
authors.forename: Guowang
authors.initials: G
authors.lastname: Diao
keywords: Mn3O4; core-shells; interaction mechanisms; lithium-sulfur batteries; phase transformation; γ-MnO2