高比能高功率全石墨烯锂离子电容器

All Graphene Lithium Ion Capacitor with High-Energy-Power Density Performance

石墨烯由于拥有超高比表面积和超高电导率而被作为电化学电容器材料广泛研究.本文采用树脂为碳源,通过一种方便快捷的树脂交换法制备一种具有高比表面积的多级孔三维石墨烯(3DG).经过此种方法的催化、造孔、热处理等主要工艺步骤后,可显著增加石墨烯材料的小、介孔数量,从而提高材料的电化学性能.通过BET测试表明,3DG的比表面积可达2400 m^2/g,孔体积达到2.0 cm^3/g.以3DG作为正负极材料制备高比能量高功率型锂离子电容器(3DG-LIC),可使3DG-LIC的工作电压从传统超级电容器的2.5 V扩展到4.0 V,能量密度也从20 Wh/kg提高到105Wh/kg.另外,相同的化学和微观结构能很好地平衡正负极的容量及速率,使高比能量高功率的3DG-LIC具有更宽阔的应用领域.

Taking advantage of the extended specific surface area and high conductivity, graphene has been widely subjected to extensive investigations by many research groups. Herein, three-dimensional graphene（3 DG） were prepared by a facile and scalable ion-exchange method, which exhibited a porous structure with a specific surface area of 2400 m^2/g and pore volume of 2.0 cm^3/g. In a typical synthesis, two key procedures played an important role in preparing the novel characteristics of 3 DG： First, metal ions were used as the catalysis to graphitize the ion-exchange resin. Second, an KOH activation step at low temperatures（800 ℃） was applied on the exchange resin to produce a hierarchical porous structure of 3 DG materials. The method of catalysis, chemical activation and heating treatment can form a unique interconnected structure and also effectively prevent graphene nanosheets from aggregating. Various structural and morphology analyses have been characterized by X-ray powder diffraction, Raman, Scanning electron microscope and Transmission electron microscope. Additionally, the enhanced specific surface area can improve capacitor performance of 3 DG, which exhibited a high specific capacitance of 250 F/g when measured in a three-electrode system（KOH aqueous solution） and 120 F/g in a symmetric supercapacitor（TEMABF4/PC organic electrolytes）. Furthermore, the as-prepared 3 DG were successfully employed as both cathode and anode active materials for lithium ion capacitors（3 DG-LIC） with high energy density（105 Wh/kg） because the potential window of 3 DG-LIC extended from 2.5 to 4.0 V compared to traditional supercapacitor（SC） by prelithiation of anode. The performance and operating mechanism of 3 DG-LIC were further studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The similar chemistry and microstructure maximizes the capacity and rate performance of cathode and anode, which indicates that the 3 DG-LIC can be a promising candidate for high-energypower storage system and would have a wide application in other electrochemical applications.