It is interesting to convert industrial pitch to carbon based materials with high yield for energy storage owing to environmental and energy concerns. In this study, we activated coal tar pitch by a green process to obtain porous carbon sheets sandwiched by graphene, and further impregnated with 71% sulphur as the cathode for long-term cycling lithium–sulphur battery. In the presence of 4.0% of electrochemically exfoliated graphene flakes, the yield of carbon from pitch is as high as 72%, while the activation temperature of the pitch is as low as 700 °C. This carbon sheet has a high specific surface area of 2930 m² g⁻¹ and large pore volume of 1.5 cm³ g⁻¹, which is nearly 3 times that of activated carbon derived from pitch without graphene. The cathode loaded with 71% sulfur (3.0 mg cm⁻² of sulphur) demonstrated a discharge capacity of 1340 mA h g⁻¹ at 0.05 C, which faded by only 0.001% per cycle at 1 C during 201–1500 cycles. Surface oxygen groups, 1.1 nm nanopore confinement and the sandwich structure of conductive graphene may contribute to the stable and reversible electrochemical reaction of the Li and sulphur clusters. Our investigation demonstrates that graphene can enhance the pitch activation to high quality microporous carbon and further confine sulphur species for long-term cycling Li–S batteries.

中文翻译：

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石墨烯对长周期Li–S电池的沥青活化作用的改善

出于环境和能源方面的考虑，将工业沥青转化为具有高收率的碳基材料用于储能是有趣的。在这项研究中，我们通过绿色工艺活化了煤焦油沥青，从而获得了被石墨烯夹在中间的多孔碳板，并进一步浸渍了71％的硫作为长期循环锂硫电池的阴极。在存在4.0％的电化学剥落石墨烯薄片的情况下，沥青的碳收率高达72％，而沥青的活化温度则低至700°C。该碳片的比表面积高，为2930m ² g ^-1，大孔容积为1.5cm ³ g ^-1。，这几乎是不含石墨烯的沥青衍生的活性炭的3倍。负载了71％硫（3.0 mg cm ^-2的硫）的阴极在0.05 C时的放电容量为1340 mA hg ^-1，在201-1500个循环中，在1 C时，每个循环仅降低0.001％。表面氧基团，1.1 nm纳米孔限制和导电石墨烯的夹心结构可能有助于Li和硫簇的稳定和可逆的电化学反应。我们的研究表明，石墨烯可以增强沥青质对高品质微孔碳的活化作用，并进一步限制长期循环使用的Li-S电池的硫种类。