Core–Shell Structure and Interaction Mechanism of

γ-MnO₂Coated Sulfur for Improved Lithium-Sulfur Batteries

Lubin Ni,^a* Zhen Wu,^aGangjin Zhao,^aChunyu Sun,^aChuanqiang Zhou,^bXiangXiang Gong,^band Guowang Diao^a*

^aCollege of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu, People’s Republic of China.

^bTesting Center，Yangzhou University，Yangzhou, 225002 Jiangsu, People’s Republic of China.

Abstract:Lithium-sulfur batteries have attracted worldwide interest due to their high theoreticalcapacity of 1672 mAh g−1 and low cost. However, the practical applications arehampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, theauthors have fabricated a solid core–shellγ-MnO₂-coated sulfur nanocompositethrough the redox reaction between KMnO₄and MnSO₄. The multifunctionalMnO₂shell facilitates electron and Li+transport as well as efficiently preventspolysulfide dissolution via physical confinement and chemical interaction. Moreover,theγ-MnO₂crystallographic form also provides one-dimensional (1D) tunnels forthe Li+incorporation to alleviate insoluble Li₂S₂/Li₂S deposition at high dischargerate. More importantly, the MnO₂phase transformation to Mn₃O₄occurs duringthe redox reaction between polysulfides andγ-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 degradationmechanism can probably be elucidated that the decomposition of the surface Mn₃O₄phase is the cause of polysulfide dissolution. The recent work thus sheds new light onthe hitherto unknown surface interaction mechanism and the degradation mechanismof Li-S cells.

Small.2017, DOI:10.1002/smll.201603466.IF：8.315

文章链接:http://onlinelibrary.wiley.com/wol1/doi/10.1002/smll.201603466/full