Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering , Beijing Institute of Technology , Beijing 100081 , China.
Aerospace Institute of Advanced Materials & Processing Technology , Beijing 100074 , China.
ACS Appl Mater Interfaces. 2019 Apr 3;11(13):12544-12553. doi: 10.1021/acsami.9b00845. Epub 2019 Mar 25.
For lithium-sulfur (Li-S) batteries, a promising candidate for future high-energy storage devices, several prominent problems still need to be solved urgently, such as limited rate capability and poor cycle life caused by the insulating nature of sulfur and the shuttle of soluble polysulfides produced during battery operation. In this work, a facile vacuum filtration method is employed to graft polyethyleneimine to reduced graphene oxide (rGO) in a "hand-in-hand" way using the amino and catechol groups from polydopamine. The resulting polymer-reinforced rGO (PPG) film is applied as a free-standing auxiliary functional layer for Li-S batteries. It has been confirmed by both theoretical calculations and experimental methods that, benefiting from the rich amine groups and oxygen-containing functional groups, the as-prepared PPG composite film shows great ability to capture polysulfides. Moreover, its high conductivity enables itself to function as a polysulfide reservoir, thus facilitating the successive reutilization of the trapped active materials and improving sulfur utilization. For this reason, the PPG film can also be regarded as a cathode material, serving as a novel "SPPG cathode" together with the pure sulfur cathode. The cell assembled with the pure sulfur cathode and the PPG auxiliary functional layer displays high reversible capacity, excellent Coulombic efficiency, and good cycling stability, suggesting that the rational auxiliary functional layer design ensures a good match with pure sulfur cathodes and shows the potential to achieve energy-dense Li-S batteries.
对于锂硫（Li-S）电池，作为未来高能量存储设备的有前途的候选者，仍有几个突出的问题亟待解决，例如硫的绝缘性质和电池运行过程中产生的可溶性多硫化物的穿梭导致的有限倍率性能和较差的循环寿命。在这项工作中，采用简便的真空过滤法，使用多巴胺中的氨基和邻苯二酚基团，以“手牵手”的方式将聚乙烯亚胺接枝到还原氧化石墨烯（rGO）上。所得聚合物增强的 rGO（PPG）薄膜被用作 Li-S 电池的独立辅助功能层。通过理论计算和实验方法都证实了，得益于丰富的胺基和含氧官能团，所制备的 PPG 复合薄膜具有出色的捕集多硫化物的能力。此外，其高导电性使其能够作为多硫化物的储存库，从而促进了捕获的活性材料的连续再利用，提高了硫的利用率。因此，PPG 薄膜也可以被视为一种阴极材料，与纯硫阴极一起构成新型的“SPPG 阴极”。由纯硫阴极和 PPG 辅助功能层组装的电池表现出高可逆容量、优异的库仑效率和良好的循环稳定性，这表明合理的辅助功能层设计确保了与纯硫阴极的良好匹配，并显示出实现能量密集型 Li-S 电池的潜力。
