College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
Testing Center, Yangzhou University, Yangzhou, 225002, Jiangsu, P. R. China.
Small. 2017 Apr;13(14). doi: 10.1002/smll.201603466. Epub 2017 Jan 30.
Lithium-sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g 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 -coated sulfur nanocomposite through the redox reaction between KMnO and MnSO . The multifunctional MnO shell facilitates electron and Li transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ-MnO crystallographic form also provides one-dimensional (1D) tunnels for the Li incorporation to alleviate insoluble Li S /Li S deposition at high discharge rate. More importantly, the MnO phase transformation to Mn O occurs during the redox reaction between polysulfides and γ-MnO is first thoroughly investigated. The S@γ-MnO 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 O 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.
锂硫电池因其高达 1672 mAh g 的理论容量和低成本而引起了全球的关注。然而，其实际应用受到容量衰减的阻碍，主要归因于多硫化物穿梭。在这里，作者通过 KMnO 和 MnSO 之间的氧化还原反应，制备了一种具有核壳结构的 γ-MnO 包覆的硫纳米复合材料。多功能 MnO 壳层通过物理限制和化学相互作用，促进了电子和 Li 的传输，并有效地阻止了多硫化物的溶解。此外，γ-MnO 的晶型也为 Li 的掺入提供了一维（1D）隧道，以缓解在高放电速率下不可溶的 Li S /Li S 的沉积。更重要的是，首次彻底研究了多硫化物与 γ-MnO 之间的氧化还原反应过程中 MnO 相的转变。S@γ-MnO 复合材料在 300 次循环（0.5 C）后具有良好的容量保持率 82%，在 600 次循环（1 C）后每循环的衰减率为 0.07%。降解机理可能可以解释为表面 Mn O 相的分解是多硫化物溶解的原因。这项最新工作为 Li-S 电池的未知表面相互作用机制和降解机制提供了新的认识。
