Xu Xinbo, Ruan Jiafeng, Pang Yuepeng, Yuan Tao, Zheng Shiyou
School of Materials Science and Engineering, University of Shanghai for Science and Technology Shanghai 200093 China
Shanghai Innovation Institute for Materials Shanghai 200444 China.
RSC Adv. 2018 Jan 31;8(10):5298-5305. doi: 10.1039/c7ra12694h. eCollection 2018 Jan 29.
Rechargeable Li-S batteries are receiving ever-increasing attention due to their high theoretical energy density and inexpensive raw sulfur materials. However, their practical applications have been hindered by short cycle life and limited power density owing to the poor electronic conductivity of sulfur species, diffusion of soluble polysulfide intermediates (LiS , = 4-8) and the large volume change of the S cathode during charge/discharge. Optimizing the carbon framework is considered as an effective approach for constructing high performance S/carbon cathodes because the microstructure of the carbon host plays an important role in stabilizing S and restricting the "shuttle reaction" of polysulfides in Li-S batteries. In this work, reduced graphite oxide (rGO) materials with different oxidation degree were investigated as the matrix to load the active material by an thermally reducing graphite oxide (GO) and intercalation strategy under vacuum at 600 °C. It has been found that the loaded amount of S embedded in the rGO layer for the S/carbon cathode and its electrochemical performance strongly depended on the oxidation degree of GO. In particular, on undergoing CS treatment, the rGO-S cathode exhibits extraordinary performances in Li-S batteries. For instance, at a current density of 0.2 A g, the optimized rGO-S cathode shows a columbic efficiency close to 100% and retains a capacity of around 750 mA h g with progressive cycling up to over 250 cycles.
可充电锂硫电池因其高理论能量密度和廉价的原料硫而受到越来越多的关注。然而，由于硫物种的电子导电性差、可溶性多硫化物中间体（LiS ， = 4 - 8）的扩散以及硫阴极在充放电过程中的大体积变化，其实际应用受到了循环寿命短和功率密度有限的阻碍。优化碳骨架被认为是构建高性能硫/碳阴极的有效方法，因为碳载体的微观结构在稳定硫和限制锂硫电池中多硫化物的“穿梭反应”方面起着重要作用。在这项工作中，通过在600℃真空下热还原氧化石墨烯（GO）和插层策略，研究了不同氧化程度的还原氧化石墨烯（rGO）材料作为负载活性材料的基质。已经发现，硫/碳阴极嵌入rGO层中的硫负载量及其电化学性能强烈依赖于GO的氧化程度。特别是，经过CS处理后，rGO-S阴极在锂硫电池中表现出非凡的性能。例如，在0.2 A g的电流密度下，优化后的rGO-S阴极显示出接近100%的库仑效率，并在超过250次循环的渐进循环中保持约750 mA h g的容量。
