Sulfur possesses a high specific capacity as a rechargeable lithium battery cathode. However, the commercial applications of sulfur cathodes are limited by the poor electronic/ionic conductivity of elemental sulfur and polysulfides, volume expansion of sulfur during the discharge process, and the high solubility of long-chain lithium polysulfides (Li2Sn, 4 <= n <= 8). Herein, we design a core-shell structure composed of active carbon (AC) and an amorphous carbon-coating layer to encapsulate the sulfur in the carbon matrix. The carbon-coating layer obtained from the hydrothermal carbonization of glucose can effectively entrap the polysulfides. Furthermore, the composite matrix provides a conducting framework serving as an electrochemical reaction chamber for the sulfur cathode. After wrapping AC-S with an amorphous carbon layer, the obtained composite cathode can effectively confine the polysulfides and buffer the volume change. Consequently, the resulting composite cathode possesses a high specific capacity, good rate capability, and stable cycling performance. At 0.2 A g(-1) current density, the as-prepared carbon-coated AC-S composite cathode shows a high specific discharge capacity of 1103 mA h g(-1). At a current density of 0.8 A g(-1) and 1.6 A g(-1), the composite cathode exhibits 75% capacity retention over 150 cycles. The Coulombic efficiency of the cell remains at approximately 95%.
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机译：硫具有高的比容量作为可再充电锂电池阴极。但是，硫阴极的商业应用受到元素硫和多硫化物的不良电子/离子电导率，放电过程中硫的体积膨胀以及长链多硫化锂的高溶解度（Li2Sn，4 <= n < = 8）。本文中，我们设计了一种由活性炭（AC）和无定形碳涂层组成的核-壳结构，将硫包裹在碳基质中。由葡萄糖的水热碳化获得的碳涂层可以有效地截留多硫化物。此外，复合基质提供了用作硫阴极的电化学反应室的导电框架。用非晶碳层包裹AC-S后，所得复合阴极可有效地限制多硫化物并缓冲体积变化。因此，所得的复合阴极具有高的比容量，良好的倍率容量和稳定的循环性能。在0.2 A g（-1）的电流密度下，所制备的碳包覆的AC-S复合阴极显示出1103 mA h g（-1）的高比放电容量。在0.8 A g（-1）和1.6 A g（-1）的电流密度下，复合阴极在150个循环中显示出75％的容量保持率。细胞的库仑效率保持在大约95％。
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