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Core–Shell Structure and Interaction Mechanism of γ‐MnO 2 Coated Sulfur for Improved Lithium‐Sulfur Batteries
Author(s) -
Ni Lubin,
Wu Zhen,
Zhao Gangjin,
Sun Chunyu,
Zhou Chuanqiang,
Gong XiangXiang,
Diao Guowang
Publication year - 2017
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201603466
Subject(s) - polysulfide , dissolution , sulfur , redox , chemical engineering , materials science , lithium (medication) , degradation (telecommunications) , phase (matter) , reaction mechanism , chemistry , electrode , electrolyte , metallurgy , catalysis , organic chemistry , medicine , telecommunications , engineering , endocrinology , computer science
Lithium‐sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g −1 and 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‐MnO 2 ‐coated sulfur nanocomposite through the redox reaction between KMnO 4 and MnSO 4 . The multifunctional MnO 2 shell facilitates electron and Li + transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ‐MnO 2 crystallographic form also provides one‐dimensional (1D) tunnels for the Li + incorporation to alleviate insoluble Li 2 S 2 /Li 2 S deposition at high discharge rate. More importantly, the MnO 2 phase transformation to Mn 3 O 4 occurs during the redox reaction between polysulfides and γ‐MnO 2 is first thoroughly investigated. The S@γ‐MnO 2 composite 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 Mn 3 O 4 phase 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.