共轭纳米孔聚合物在锂硫电池中的应用

作为一类由共轭单元构建的多孔材料,共轭纳米孔聚合物（CNPs）具有开放的孔骨架、高的比表面积、永久的微孔-介孔、共轭结构以及可灵活设计的孔壁化学环境,有望成为一类理想的宿主材料,实现从分子和纳米尺度上固定或捕获客体。锂硫电池具有比能量高、成本低、环境友好等优势,是一种非常有前景的高比能锂二次电池;然而,硫的分步还原或氧化过程中产生的中间态多硫化物在电解液中的溶解穿梭现象,是导致电池循环稳定性差的根本原因之一。构建束缚多硫化物的宿主材料是锂硫电池性能突破的关键。CNPs由于其结构优势,有望成为性能优良的硫宿主材料。本文综述了近年来CNPs在锂硫电池中的应用,重点讨论了抑制"穿梭效应"提升电池性能的策略与方法,并对未来该领域的发展进行了展望。

Application of Conjugated Nanoporous Polymers for Lithium-Sulfur Batteries

As a class of porous polymeric materials constructed by the conjugated building blocks, conjugated nanoporous polymers (CNPs) exhibit open framework structures, high surface areas, permanent micro-or mesopores, conjugated skeletons, and the flexible molecular design from predefined building blocks for both porous skeleton and pore surface. Therefore, they offer a promising platform as a class of ideal host matrices for immobilization/entrapment of guest molecules or materials at molecular and nanoscale level. Lithium-sulfur (Li-S) batteries are regarded as a kind of promising high-density energy-storage technology due to their relatively high theoretical capacity, low cost and environmental benignity. However, one of the critical problems is the shuttling of soluble polysulfides in organic electrolyte derived from stepwise redox transformation between S and Li₂S, giving rise to the rapid capacity fading. Constructing sulfur hosts with efficient polysulfides immobilization ability is critical to make a breakthrough in Li-S batteries. Using CNPs as host materials is a feasible strategy, which benefitted from their unique structural features. Compared to traditional polymers, CNPs have sufficient nanopores, which can provide space to load sulfur and physical confinement towards polysulfides, thus restricting the dissolution and shuttle of polysulfides. Moreover, by designing special functionalities either on the pore skeleton or on the pore wall, chemical interactions/affinities with polysulfides can be created in CNPs. As a result, both physical confinements and chemical adsorption can be simultaneously realized so as to further inhibit the shuttle effect, thus improving the performance of Li-S batteries. This review summarizes the progress of CNPs used in Li-S batteries in recent years, focuses on the strategies of CNPs in preventing shuttle effect and boosting performance of Li-S batteries, and finally presents a perspective on the future development in this field.