Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2 V4, Canada.
ACS Nano. 2013 Jun 25;7(6):5131-41. doi: 10.1021/nn400731g. Epub 2013 May 9.
We created unique interconnected partially graphitic carbon nanosheets (10-30 nm in thickness) with high specific surface area (up to 2287 m(2) g(-1)), significant volume fraction of mesoporosity (up to 58%), and good electrical conductivity (211-226 S m(-1)) from hemp bast fiber. The nanosheets are ideally suited for low (down to 0 °C) through high (100 °C) temperature ionic-liquid-based supercapacitor applications: At 0 °C and a current density of 10 A g(-1), the electrode maintains a remarkable capacitance of 106 F g(-1). At 20, 60, and 100 °C and an extreme current density of 100 A g(-1), there is excellent capacitance retention (72-92%) with the specific capacitances being 113, 144, and 142 F g(-1), respectively. These characteristics favorably place the materials on a Ragone chart providing among the best power-energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor: At a very high power density of 20 kW kg(-1) and 20, 60, and 100 °C, the energy densities are 19, 34, and 40 Wh kg(-1), respectively. Moreover the assembled supercapacitor device yields a maximum energy density of 12 Wh kg(-1), which is higher than that of commercially available supercapacitors. By taking advantage of the complex multilayered structure of a hemp bast fiber precursor, such exquisite carbons were able to be achieved by simple hydrothermal carbonization combined with activation. This novel precursor-synthesis route presents a great potential for facile large-scale production of high-performance carbons for a variety of diverse applications including energy storage.
我们从大麻韧皮纤维中制造出具有独特互联的部分石墨化碳纳米片（厚度为 10-30nm），其具有高比表面积（高达 2287 m(2) g(-1))、显著的中孔体积分数（高达 58%）和良好的导电性（211-226 S m(-1))。这些纳米片非常适合在低（低至 0°C）至高（100°C）温度离子液体基超级电容器应用中使用：在 0°C 和 10 A g(-1)的电流密度下，电极保持着高达 106 F g(-1)的显著电容。在 20°C、60°C 和 100°C 以及极端电流密度 100 A g(-1)下，仍具有出色的电容保持率（72-92%），比电容分别为 113、144 和 142 F g(-1)。这些特性使这些材料在拉贡图上具有优异的功率-能量特性（基于活性质量归一化），是迄今为止报道的电化学电容器中最好的特性之一：在非常高的功率密度 20 kW kg(-1)和 20°C、60°C 和 100°C 下，能量密度分别为 19、34 和 40 Wh kg(-1)。此外，组装好的超级电容器装置的最大能量密度为 12 Wh kg(-1)，高于市售超级电容器。通过利用大麻韧皮纤维前体的复杂多层结构，通过简单的水热碳化结合活化，能够实现这种精致的碳。这种新型的前体合成路线为各种不同应用（包括储能）的高性能碳的简便大规模生产提供了巨大的潜力。
