Small organic molecules with electrochemically active functional groups can achieve high-density energy storage by the reversible Faraday reaction of multiple electrons. However, poor conductivity has hindered their wide application in the field of energy storage. Graphene hydrogel (GH), a graphene derivative, has a three-dimensional porous network, and the three-dimensional network efficiently releases graphene’s true surface by preventing graphene from building up. Therefore, compared with graphene, graphene hydrogels are more suitable as substrate materials. In the present article, the small organic molecule quinoline-2,3-dicarboxylic acid (QDC) is successfully modified on GH by a hydrothermal method to obtain a carbon-based electrode material, QDC/GH. QDC/GH displays excellent capacitive property with a specific capacitance of 512 F g^–1 at 1 A g^–1. Importantly, the cycling stability test indicates that the capacitance retention is close to 99% after 10,000 cycles at 5 A g^–1. To explore the practical implementation of QDC/GH, an asymmetric supercapacitor QDC/GH//AC is assembled, which uses QDC/GH as the positive electrode material and activated carbon (AC) as the negative electrode material. Compared with other devices, the device shows a high energy density, reaching 37.7 W h kg^–1 at a power density of 905 W kg^–1. The energy density is higher than that of most of the organic molecular capacitors that have been reported. In addition, two devices can be used in series to light 52 LED bulbs. By organic molecular modification, GH’s capacitance performance can be further improved, and its application to energy storage can be further expanded.

中文翻译：

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用于高性能不对称超级电容器的喹啉-2,3-二甲酸改性石墨烯水凝胶复合材料

具有电化学活性官能团的有机小分子可以通过多电子的可逆法拉第反应实现高密度能量存储。然而，较差的导电性阻碍了其在储能领域的广泛应用。石墨烯水凝胶（GH）是一种石墨烯衍生物，具有三维多孔网络，三维网络通过阻止石墨烯堆积来有效释放石墨烯的真实表面。因此，与石墨烯相比，石墨烯水凝胶更适合作为基底材料。本文通过水热法成功对有机小分子喹啉-2,3-二甲酸（QDC）进行修饰，得到碳基电极材料QDC/GH。 QDC/GH 显示出优异的电容特性，在 1 A g ^–1时比电容为 512 F g ^–1。重要的是，循环稳定性测试表明，在 5 A g ^–1下循环 10,000 次后，电容保持率接近 99% 。为了探索QDC/GH的实际应用，组装了一种不对称超级电容器QDC/GH//AC，它使用QDC/GH作为正极材料，活性炭（AC）作为负极材料。与其他器件相比，该器件表现出较高的能量密度，在功率密度为905 W kg ^{–1时达到37.7 W h kg –1}。能量密度高于大多数已报道的有机分子电容器。此外，两个设备串联使用可以点亮52个LED灯泡。通过有机分子修饰，可以进一步提高GH的电容性能，进一步拓展其在储能方面的应用。