Yang He, Yang Yanan, Zhang Xu, Li Yongpeng, Qaisrani Naeem Akhtar, Zhang Fengxiang, Hao Ce
State Key Laboratory of Fine Chemicals, School of Petroleum & Chemical Engineering , Dalian University of Technology , Panjin 124221 , China.
ACS Appl Mater Interfaces. 2019 Sep 4;11(35):31860-31868. doi: 10.1021/acsami.9b08962. Epub 2019 Aug 23.
The practical development of lithium-sulfur (Li-S) batteries is largely obstructed by their poor cycling stability due to the shuttling effect of soluble polysulfides. To address this issue, we herein report an interconnected porous N-doped carbon network (NPCN) incorporating FeC nanoparticles and Fe-N moieties, which is used for separator modification. The NPCN can facilitate lithium ion and electron transport and localize polysulfides within the separator's cathode side due to strong chemisorption; the FeC/Fe-N species also provides chemical adsorption to trap polysulfides and FeC catalyzes the redox conversion of polysulfides. More importantly, the catalysis effect of FeC is promoted by the presence of Fe-N coordination sites as indicated by the enhanced redox current in cyclic voltammetry. Due to the above synergistic effects, the battery with the FeC/Fe-N@NPCN modified separator exhibits high capacity and good cycling performance: at a current density of 0.1C, it yields a high capacity of 1517 mAh g with 1.2 mg cm sulfur loading and only experiences a capacity decay rate of 0.034% per cycle after 500 cycles at 1C; it also delivers a good capacity of 683 mAh g at 0.1C with a high sulfur loading of 5.0 mg cm; after 200 cycles, the battery capacity can still reach 596 mAh g, corresponding to 87% capacity retention. Our work provides a new and effective strategy to achieve the catalytic conversion of polysulfide and is beneficial for the development of rechargeable Li-S batteries.
锂硫（Li-S）电池的实际发展在很大程度上受到其循环稳定性差的阻碍，这是由于可溶性多硫化物的穿梭效应所致。为了解决这个问题，我们在此报告一种包含FeC纳米颗粒和Fe-N部分的互连多孔氮掺杂碳网络（NPCN），用于隔膜改性。NPCN可促进锂离子和电子传输，并由于强化学吸附作用将多硫化物定位在隔膜的阴极侧；FeC/Fe-N物种还提供化学吸附以捕获多硫化物，并且FeC催化多硫化物的氧化还原转化。更重要的是，循环伏安法中增强的氧化还原电流表明，Fe-N配位位点的存在促进了FeC的催化作用。由于上述协同效应，采用FeC/Fe-N@NPCN改性隔膜的电池表现出高容量和良好的循环性能：在0.1C的电流密度下，对于1.2 mg cm的硫负载量，其产生1517 mAh g的高容量，并且在1C下500次循环后，仅经历每循环0.034%的容量衰减率；在0.1C下对于5.0 mg cm的高硫负载量，其也具有683 mAh g的良好容量；200次循环后，电池容量仍可达到596 mAh g，对应于87%的容量保持率。我们的工作为实现多硫化物的催化转化提供了一种新的有效策略，有利于可充电锂硫电池的发展。
