Pu Yujie, Wu Wubin, Liu Jianyu, Liu Tao, Ding Fei, Zhang Jing, Tang Zhiyuan
Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University Tianjin 300072 PR China
National Key Laboratory of Science and Technology on Power Sources, Tianjin Institute of Power Sources Tianjin 300384 PR China
RSC Adv. 2018 May 22;8(33):18604-18612. doi: 10.1039/c8ra02254b. eCollection 2018 May 17.
Metal organic frameworks (MOFs) have been deemed among the most promising sulfur hosts for lithium-sulfur (Li-S) batteries owing to their high specific surface areas, novel pore structures and open metal sites. However, their highly coordinated, electronically insulating and structurally unstable nature overshadows the merits of MOFs to a great extent. In this work, a novel UiO-66/carbon nanotube (UC) composite was initially synthesized a facile one-pot synthesis strategy, in which abundant linker-missing defects were caused by introduced competitive coordination. Meanwhile, flexible and interlaced carbon nanotubes (CNTs) throughout mechanically stable UiO-66 nanoparticles constructed a reliable conductive network. Because of its superior structural stability, high electronic conductivity and strong polysulfide chemisorption, the UC architecture as the sulfur cathode in Li-S batteries shows stable cycling, delivering an initial capacity of 925 mA h g at 0.5 A g and a very low fading rate over 800 cycles of 0.071% per cycle at 1 A g. A strong chemical affinity between coordination defects and LiPSs was revealed by first principles calculations and apparent absorption, which indicates significant entrapment of soluble polysulfides by the UC composite, thus leading to the outstanding cycling performance of S@UC electrodes.
金属有机框架材料（MOFs）因其高比表面积、新颖的孔结构和开放的金属位点，被认为是锂硫（Li-S）电池中最具潜力的硫宿主材料之一。然而，其高度配位、电子绝缘和结构不稳定的特性在很大程度上掩盖了MOF的优点。在这项工作中，通过一种简便的一锅合成策略，首次合成了一种新型的UiO-66/碳纳米管（UC）复合材料，其中引入的竞争配位导致了大量的连接体缺失缺陷。同时，贯穿机械稳定的UiO-66纳米颗粒的柔性交织碳纳米管（CNTs）构建了一个可靠的导电网络。由于其优异的结构稳定性、高电子导电性和强多硫化物化学吸附性，UC结构作为Li-S电池中的硫阴极表现出稳定的循环性能，在0.5 A g下初始容量为925 mA h g，在1 A g下800次循环中每循环的衰减率极低，仅为0.071%。第一性原理计算和表观吸收揭示了配位缺陷与多硫化锂之间的强化学亲和力，这表明UC复合材料对可溶性多硫化物有显著的捕获作用，从而导致S@UC电极具有出色的循环性能。
