摘要/Abstract
共轭微孔聚合物由于其高的比表面积、优良的物理化学稳定性以及沿分子链延伸的共轭结构等特点，使其在锂离子电池电极材料方面具有巨大的应用前景.本工作以四溴芘和对苯二硼酸为构建单元，通过Suzuki偶联反应合成了具有高比表面积的芘基共轭微孔聚合物PyDB，并研究了其作为锂离子电池电极材料的电化学性能.当PyDB用作锂离子电池正极材料时，在50 mA·g-1的电流密度下，放电容量达到163 mAh·g-1，即使在3000 mA·g-1的电流密度下仍具有62 mAh·g-1的可逆容量，在100 mA·g-1的电流密度下循环300次仍具有167 mAh·g-1的容量.当该聚合物用作负极材料时，在50 mA·g-1电流密度下的放电容量达到495 mAh·g-1，在200 mA·g-1的电流密度下循环300次，仍具有245 mAh·g-1的容量.PyDB优异的电化学性能主要归因于其延伸的共轭结构和高比表面积的多孔结构，大的共轭结构有利于分子链的掺杂反应和电子传导，高比表面积的多孔结构有利于提供大量的活性位点并促进离子的迁移.
关键词: 共轭微孔聚合物, 四溴芘, 锂离子电池, 电极材料
Lithium ion batteries (LIBs) have been recognized as one of the most popular and promising energy storage devices because of their high energy density and cyclability. The leading electrode materials for LIBs are mainly based on inorganic compounds materials because of their excellent electrochemical performances. Compared with inorganic compounds or metal-based electrode materials, organic electrode materials have been less explored for LIBs, but they are promising because of their synthetic diversity, flexible framework, low cost and environmental benignity. Unlike organic small molecules and linear polymers electrodes, which show low surface area and are soluble in electrolyte leading to the low electrochemical performance, conjugated microporous polymers (CMPs) feature with large specific surface area, good physicochemical stability, unique extended π-conjugation along the polymer skeleton and high crosslinked degree, which make CMPs great potential as electrodes for LIBs. In this work, a pyrene-based conjugated microporous polymer (PyDB) has been synthesized via palladium-catalyzed Suzuki cross-coupling reaction from tetrabromopyrene and 1,4-benzenediboronic acid. PyDB is insoluble in common organic solvents tested because of its highly crosslinked polymer structure. Thermogravimetric analysis indicated that the polymer is thermally stable up to 430℃ in nitrogen atmosphere. Nitrogen adsorption-desorption measurement revealed that PyDB has a high Brunauer-Emmet-Teller specific surface area of up to 1283 m2·g-1. PyDB based electrode for LIBs exhibited excellent electrochemical performance. The assembled LIB from PyDB as cathode material shows a discharge capacity of 163 mAh·g-1 at a current density of 50 mA·g-1 with a high capacitance retention of 167 mAh·g-1 after 300 cycles at a current density of 100 mA·g-1. When PyDB was used as anode material, the assembled LIB also exhibits a high capacity of 495 mAh·g-1 at 50 mA·g-1 with a high capacitance retention of 245 mAh·g-1 after 300 cycles at 200 mA·g-1. The excellent electrochemical performance of PyDB could be attributed to its extended π-conjugation structure and porous structure with high surface area, the extended π-conjugation is beneficial to the doping reaction and electronic conduction, while porous structure with high surface area can provide plentiful active sites and promote the transmission of ions.
Key words: conjugated microporous polymer, tetrabromopyrene, lithium-ion battery, electrode material
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