Zhao Yi, Liu Jinzhang, Zheng Dezhi, Wang Bin, Hu Mingjun, Sha Jiangbo, Li Yan
School of Materials Science and Engineering, Beihang University, Beijing, 100191, China.
Small. 2018 Feb;14(8). doi: 10.1002/smll.201702809. Epub 2017 Dec 21.
To date, graphene-based electric double layer supercapacitors have not shown the remarkable specific capacitance as theoretically predicted. An efficient strategy toward boosting the overall capacitance is to endow graphene with pseudocapacitance. Herein, molecules of hydrolyzed polyimide (HPI) are used to functionalize N-doped graphene (NG) via π-π interaction and the resulting enhanced electrochemical energy storage is reported. These aromatic molecules in monolayer form on graphene contribute strong pseudocapacitance. Paper-like NG films with different areal mass loadings ranging from 0.5 to 4.8 mg cm are prepared for supercapacitor electrodes. It is shown that the gravimetric capacitance can be increased by 50-60% after the surface functionalization by HPI molecules. A high specific capacitance of 553 F g at 5 mV s is achieved by the HPI-NG film with a graphene mass loading of 0.5 mg cm in H SO aqueous electrolyte. For the HPI-NG film with highest mass loading, the gravimetric specific capacitance drops to 340 F g while the areal specific capacitance reaches a high value of 1.7 F cm . HPI-NG films are also tested in Li SO aqueous electrolyte, over an extended voltage window of 1.6 V. High specific energy densities up to 40 Wh kg are achieved with the Li SO electrolyte.
迄今为止，基于石墨烯的双电层超级电容器尚未展现出理论预测的显著比电容。提高整体电容的有效策略是赋予石墨烯赝电容。在此，水解聚酰亚胺（HPI）分子通过π-π相互作用对氮掺杂石墨烯（NG）进行功能化，并报道了由此增强的电化学储能性能。这些以单层形式存在于石墨烯上的芳香族分子贡献了强大的赝电容。制备了面质量负载范围为0.5至4.8 mg/cm²的纸状NG薄膜用于超级电容器电极。结果表明，经HPI分子表面功能化后，重量电容可提高50 - 60%。在硫酸水溶液电解质中，石墨烯质量负载为0.5 mg/cm²的HPI-NG薄膜在5 mV/s时实现了553 F/g的高比电容。对于质量负载最高的HPI-NG薄膜，重量比电容降至340 F/g，而面积比电容达到1.7 F/cm²的高值。HPI-NG薄膜也在硫酸锂水溶液电解质中进行了测试，在1.6 V的扩展电压窗口内。使用硫酸锂电解质可实现高达40 Wh/kg的高比能量密度。
